U3 O3 - Haematological and Haemostatic Emergencies Flashcards

Question

What type of disease is Babesia canis and what can it cause?

Answer 1

This causes haemolytic anaemia Infection with Babesia canis or Babesia gibsoni - babesiosis. This is a tickborne, protozoal blood parasite which was previously rarely seen in the UK. However, it has become more prevalent with increased importation and the more relaxed recent pet passport scheme of recent years. It can occasionally be a cause of illness in imported dogs (Solano-Gallego, 2016). Clusters of case have been reported in the UK with dogs imported from Europe. There have also been some recent outbreaks of babesiosis in the UK in dogs that have not travelled out with the UK (Wright, 2018). Babesiosis, however, is mainly confined to North America, Asia and Africa.

Answer 2

Its a type of haemolytic anaemia Microangiopathic anaemia – mechanical damage to RBCs as they circulate. This could be associated with haemangiosarcoma, splenic torsion and heartworm disease (Goggs and Hackner, 2018). Broken RBCs (schistocytes) are often seen on blood smears from affected patients.

Answer 3

1. Immune-mediated disease 2. Toxicity 3. Drug related 4. Severe hypophosphataemia 5. Incompatible blood transfusions

Answer 4

1. Immune mediated disease- can be secondary to FeLV; or Mycoplasma haemofelis (aka haemoplasma)- (previously known as Haemobartonella felis).

Answer 5

2. Toxicity e.g. garlic and onion poisoning; lead poisoning which leads to Heinz body formation. Cat haemoglobin is very sensitive to oxidative damage and easily injured- therefore there are several causes of Heinz body anaemia in cats e.g. diabetes mellitus, hyperthyroidism, lymphoma and administration of propofol for long periods (> 12 hours)

Answer 6

3. Drug related e.g. methimazole, paracetamol

Answer 7

Severe hypophosphataemia (cats < 0.48 mmol/l) – this can occur secondary to other diseases e.g. diabetes mellitus

Answer 8

Clinical signs are usually acute onset, developing over a period of 2-3 days, and depend on the severity of the anaemia

Answer 9

Mildly affected cases may simply appear lethargic and slightly tachypnoeic. Patients with severe anaemia will be weak, obtunded and possibly collapsed. Increased intravascular haemolysis Extravascular haemolyis pulmonary thromboembolism and disseminated intravascular coagulation (DIC) are relatively common sequels to IMHA leading to respiratory distress

Answer 10

Break down of RBCs in the circulation leading to an accumulation of haemoglobin and bilirubin in soft tissue and urine. Consequently, the patient may have icteric/jaundiced mucous membranes; and haemoglobinuria where the urine is stained by haemoglobin pigment so appearing darker in colour than normal ‘port wine urine’. This indicates intravascular haemolysis

Answer 11

Increased intravascular haemolysis – break down of RBCs in the circulation leading to an accumulation of haemoglobin and bilirubin in soft tissue and urine. Consequently, the patient may have icteric/jaundiced mucous membranes; and haemoglobinuria where the urine is stained by haemoglobin pigment so appearing darker in colour than normal ‘port wine urine’. If the anaemia is severe, the patient is likely to be tachycardic with bounding pulses- cats may also have a haemic murmur. There may be splenomegaly and hepatomegaly. The clinical signs and prognosis tend to be poorer for dogs with intravascular haemolysis.

Answer 12

Extravascular haemolysis – the RBCs are phagocytosed prematurely by macrophages in the spleen, liver and bone marrow so there is less likelihood of jaundice and haemoglobinuria

Answer 13

In cats with Mycoplasma (Haemobartonella) haemofelis, three main presentations have been reported (Weingart et al., 2015) - 1. Kittens and some adults develop peracute anaemia with collapse and hypothermia 2. Kittens and most adults develop acute anaemia and fever, splenic enlargement and tachypnoea - as well as appearing generally sore all over their bodies. 3. Adult cats developing mild anaemia, mild pyrexia, lethargy and loss of weight. The condition is often more chronic.

Answer 14

There will be abnormal haematological parameters e.g. decreased PCV, RBC count and haemoglobin levels. PCV is quick and easy to check but can be affected by factors such as dehydration- total protein/ total solids (TP/TS) should be checked at the same time to gain as much information as possible e.g. the PCV will be decreased but TP/TS should be normal with IMHA. The patient may have thrombocytopaenia +/- neutrophilia.

Answer 15

A lot of information can be found from a blood smear so these should be performed routinely in any patient with anaemia (Sharkey, 2015). On a blood smear from a patient with haemolytic anaemia there is often evidence of a strong regenerative response.

Answer 16

``` Features of a regenerative response are- • large, polychromic red cells • anisocytosis • a high reticulocyte count ** • +/- an increase in the number of nucleated red cells. ```

Answer 17

‘Since a regenerative response takes approximately 3 to 5 days to mount, acute cases may initially appear poorly regenerative

Answer 18

There may be spherocytes- these are red blood cells which are spherical rather than the usual disc shape.

Answer 19

They can be present for several reasons but can be associated with IMHA- produced when macrophages remove part of the red cell wall

Answer 20

It is harder to recognise spherocytes in cat blood smears. N.B. Lack of spherocytes in a dog with haemolytic anaemia can be suggestive of zinc toxicity

Answer 21

White cell counts are also often elevated due to the increased bone marrow activity of a regenerative response.

Answer 22

Basophilic stippling of erythrocytes may be seen with lead poisoning, but this may also be seen in cats with a marked red blood cell regenerative response.

Answer 23

Heinz bodies are the result of oxidative damage to haemoglobin in the red cells and appear as refractile, poorly staining structures located beneath the red cell membrane or protruding from it. In cats, Heinz bodies are suggestive of intoxication e.g. paracetamol or onion poisoning.

Answer 24

Staining of the blood smear with new methylene blue, will demonstrate reticulocytes.

Answer 25

They have a fine trabecular structure within the cells (made up of nuclear material and cellular organelles)

Answer 26

In cats, reticulocytes may appear with punctate dots or clusters and lines of condensed organelles. These start out as the aggregate form (clusters and lines) and mature to the punctate dots. Therefore, the presence of large numbers of the aggregate form of reticulocyte, in cats, demonstrates active regeneration. The presence of immature nucleated red blood cells also demonstrates a marked regenerative response. These cells are more basophilic and much larger than the mature erythrocytes.

Answer 27

The best means of diagnosing Mycoplasma haemofelis infection is by polymerase chain reaction (PCR)

Answer 28

the organism Mycoplasma haemofelis may be found as chains, discs or rods on the surface of erythrocytes. The PCV can decrease rapidly in cats with this condition

Answer 29

With an immune mediated condition, cells destined to be destroyed are first coated with antibodies. Auto-agglutination is caused by cross-linking of the antibodies which are bound to the erythrocyte membranes- strongly suggesting that the haemolysis is immune-mediated

Answer 30

Auto-agglutination makes RBCs stick together- macroscopically this looks like small flecks, within the drop of blood on a slide; microscopically the RBCs stick to each other, looking like bunches of grapes.

Answer 31

A saline dispersion test (also called slide agglutination test) should be performed to determine if there is genuine auto-agglutination of red blood cells or if, instead, rouleaux formation has occurred. Rouleaux is a physiological clumping/stacking of red blood cells- adding saline will cause the RBCs to separate/disperse if rouleaux is present. It is not a sign of immune-mediated disease. If auto-agglutination has occurred, the RBCs will remain stuck to each other because they are coated with antibody. In this test, a drop of anticoagulated blood, from an EDTA blood tube or capillary tube, is mixed with 3 drops of saline on a microscope slide

Answer 32

Further confirmation of IMHA, can be done using both the direct and indirect Coombs test. The direct Coombs test demonstrates RBC coating with anti-RBC antibodies; the indirect Coombs test demonstrates the presence of anti- RBC antibodies in serum. The Coombs test is of debatable value being very specific but not very sensitive. It also needs to be carried out by an external laboratory- due to the critical nature of many of these patients, presumptive treatment is likely to be required before the results come back.

Answer 33

Radiography | Metallic foreign material e.g. coins may be visible on abdominal radiographs in dogs with zinc toxicity

Answer 34

Phosphate levels should be measured, particularly in cats as levels <0.48mmol/L can induce haemolysis. This is a common issue in patients with diabetic ketoacidosis for example. Other causes include decreased intestinal absorption, increased renal losses and transcellular shifts

Answer 35

organ function tests, particularly for liver and kidney function, and electrolyte levels should be checked as well. Bilirubin may be increased secondary to the breakdown of the red blood cells (pre-hepatic). Renal parameters may be elevated and azotaemia is common. Assessment of renal function including urine specific gravity is important.

Answer 36

The patient should be cage rested and stress avoided to minimise additional oxygen requirements. Supplementary oxygen may be administered - however it is important to consider that the problem is not with the respiratory system but an issue with the binding and delivery of oxygen. Therefore, the hypoxia will really only improve once the haemoglobin level increases. If using supplemental oxygen techniques, consideration should be given to the potential for an anaemic patient to have a coagulopathy. Placing nasal prongs or catheters may cause significant haemorrhage. An IV catheter should be placed, on vet direction, to allow vascular access for medications, fluids and possible blood transfusion(s). Care should be taken when placing due to the increased risk of thrombus formation. Intravenous access may be challenging in these patients. Due to the immune system compromise, that can accompany some of these disease processes, an aseptic technique is absolutely vital and repeated venepuncture should be avoided. It is sometimes more successful accessing a saphenous vein that has not been used for blood sampling. Placing a central line (jugular catheter) is an option for some patients but only if certain there is not a concurrent coagulopathy.

Answer 37

With IMHA being an immune-mediated condition, immunosuppressive treatment is the main long-term treatment (e.g. prednisolone) – discussed further below. If the PCV has dropped below 20% and there are clinical signs related to anaemia, blood products may be required- packed red blood cells would be appropriate in this situation (Goggs and Hackner, 2018). However, the veterinary surgeon’s decision to transfuse (termed transfusion trigger) will be based on various factors, including clinical signs, and not just the PCV (Walton and Tappin, 2018). There are risks associated with transfusion which need to be balanced against the benefit to the patient and the effect the anaemia is having on the individual. If a patient’s own RBCs are being destroyed by antibodies, it is possible that transfused RBCs are even more likely to be destroyed, thus precipitating a serious transfusion reaction.

Answer 38

Ongoing monitoring should involve assessment of mucous membrane colour, heart rate, pulse quality, capillary refill time (CRT), PCV and patient mentation. It is important to monitor for complications e.g. sepsis/ transfusion reactions as well as meeting the patient’s basic nursing needs. Nursing care will include addressing patient comfort and ensuring they cannot cause themselves further harm; providing enrichment, if appropriate, as these patients need to be restricted; grooming; TLC and nutritional support

Answer 39

If a diagnosis of IMHA is confirmed, immunosuppressant treatment will be required e.g. corticosteroids (prednisolone in tapering doses). Other immunosuppressant therapy may be required for dogs that are refractory to treatment e.g. azathioprine or cyclosporine. These additional drugs generally permit the prednisolone dose to be reduced sooner, thus lessening the side-effects of corticosteroids on the animal. As side-effects, including bone marrow suppression may be seen, patients will need to be closely monitored during use.

Answer 40

In cats, doxycycline or oxytetracycline for 3 weeks may be required if Mycoplasma (Haemobartonella) haemofelis has been diagnosed/suspected. Doxycycline has been reported to cause oesophagitis and dogs/cats should therefore eat after administration (BSAVA, 2020) Pradofloxacin is a relatively new fluoroquinolone antibiotic reported to be effective (International Cat Care, 2018). Enrofloxacin may be used for 3 weeks but may not fully clear the parasite as well as increasing the risk of acute renal failure. Treated cats, may however, remain as carriers.

Answer 41

With IMHA, thrombo-prophylaxis using drugs such as clopidogrel or aspirin may be required- affected dogs are prone to developing thromboembolic disease (pulmonary thromboembolism, DIC or portal thrombi) which will worsen the prognosis for recovery (Goggs and Hackner, 2018) (Day, 2012). It is unclear currently what the best antithrombotic is- recent research has indicated that that unfractionated heparin or rivaroxaban could be useful (Goggs and Hackner, 2018). The American College of Veterinary Emergency and Critical Care have developed a consensus statement on the rational use of anti-thrombotics in Veterinary Critical Care

Answer 42

Zinc toxicity Immediate emergency treatment is required due to the high risk of death -IVFT (based on perfusion parameters and hydration status); GIT protectants packed red blood cell transfusion if there are clinical signs relating to the anaemia. As soon as the patient’s condition is sufficiently stable, the foreign material should be removed endoscopically or surgically (Goggs and Hackner, 2018). Removal and/or treatment of underlying causes of oxidative RBC damage is needed e.g. propofol infusion, hypophosphataemia etc

Answer 43

The classic model of coagulation, with the separate extrinsic and intrinsic pathways leading to a final common pathway resulting in blood clot formation (fibrin plug) shows how coagulation takes place in a laboratory setting (in vitro).

Answer 44

it is proposed that a different process takes place in a living patient that is bleeding (in vivo)- the cell-based model of haemostasis. This model considers the roles of cells in haemostasis in the living patient

Answer 45

Research shows that haemostasis occurs on the surface of certain cells and it involves three overlapping phases- initiation, amplification and propagation.

Answer 46

Following tissue damage, it is proposed that exposure of tissue factor to blood results in the activation of factor VII (and some other factors) – INITIATION. This leads to the production of a small amount of thrombin

Answer 47

This thrombin production activates platelets which then bind factors V, VIII, and IX on their surface (i.e. cell based) - AMPLIFICATION.

Answer 48

Once bound to platelets, the activated clotting factors lead to the conversion of large amounts of prothrombin to thrombin - PROPAGATION.

Answer 49

Research shows that haemostasis occurs on the surface of certain cells and it involves three overlapping phases- initiation, amplification and propagation. Following tissue damage, it is proposed that exposure of tissue factor to blood results in the activation of factor VII (and some other factors) – INITIATION (Sucker and Zotz, 2015). This leads to the production of a small amount of thrombin (refer to diagram above). This thrombin production activates platelets which then bind factors V, VIII, and IX on their surface (i.e. cell based) - AMPLIFICATION. Once bound to platelets, the activated clotting factors lead to the conversion of large amounts of prothrombin to thrombin - PROPAGATION. This sudden production of a large amount of thrombin (‘thrombin burst’) leads to the conversion of a large amount of fibrinogen to fibrin (the clot), as well as further activation of factor XIII. The clot is formed at the site of blood vessel injury.

Answer 50

Healthy, Intact Blood Vessel containing blood (red blood cells, white blood cells, platelets and plasma containing clotting factors (CF)). Tissue factor (TF) in blood vessel smooth muscle and outer coating - Damage to blood vessel The first phase, initiation, occurs on cells with tissue factor (TF) and leads to a small amount of thrombin being produced. N.B. Tissue factor (TF) is a protein which is on the surface of many extravascular cells, which make up the walls (not the lining) of the blood vessels e.g. vascular smooth muscle cells and adventitial cells. Normally blood would not contact cells bearing tissue factor. Therefore, if blood does encounter TF, it is because there is damage to the blood vessel meaning haemorrhage is likely to be occurring. Tissue factor is considered to be the primary initiator of blood coagulation in vivo The second phase, amplification, is when platelets and co-factors are activated. The third phase, propagation, occurs on the surface of platelets, and results in the production of large amounts of thrombin. This in turn leads to conversion of fibrinogen to fibrin and the formation of a clot at the site of the injury.

Answer 51

Disorders of primary haemostasis are generally associated with thrombocytopaenia (decreased platelet number) and, occasionally, thrombocytopathia (platelets not functioning normally).

Answer 52

Disorders of secondary haemostasis are generally associated with clotting disorders such as haemophilia A, liver disease, rodenticide poisoning (relative vitamin K deficiency) and DIC

Answer 53

History, signalment and clinical signs are important when trying to identify an underlying cause. A disorder of primary haemostasis (thrombocytopaenia or thrombopathia) usually presents with mucosal/ epithelial haemorrhage and/ or petechiation. With primary haemostatic disorders evidence of bleeding is commonly seen on the mucosa or the skin.

Answer 54

A disorder of secondary haemostasis is usually associated with a larger volume bleed e.g. haematoma and intracavity bleeding (e.g. thorax, abdomen, joints).

Answer 55

Thrombocytopaenia may occur due decreased platelet production or increased platelet use, destruction or removal from the circulation

Answer 56

Clinical signs associated with thrombocytopaenia are not likely to be apparent until the platelet count is < 40 x 109 /l

Answer 57

Thrombocytopaenia may be caused by a drug reaction e.g. cephalosporins; or platelet activity can be affected by certain drugs e.g. aspirin. Aspirin, in particular, will have a long-lasting effect on platelet function. Once administered, the platelet function remains depressed for the lifespan of the platelet, rather than the half-life of the drug e.g. the time the drug is in the animal’s system.

Answer 58

Clotting Defects Von Willebrand’s disease is caused by an absence of von Willebrand’s factor (vWF). Unlike the other clotting factors which are made in the liver, Von Willebrand’s factor is made within endothelial cells and megakaryocytes- it is an adhesive protein which is required to encourage platelet aggregation and adhesion during primary haemostasis

Answer 59

Von Willebrand’s disease is a common inherited disease in Dobermans, Rottweilers and German Shepherd Dogs

Answer 60

Haemophilia A is the most common inherited coagulation deficiency disorder in dogs

Answer 61

Haemophilia A is the most common inherited coagulation deficiency disorder in dogs. There is decreased factor VIII which is essential for the intrinsic clotting cascade.

Answer 62

Rodenticide intoxication creates a deficiency in active vitamin K - vitamin K is required by factors II (prothrombin), VII, IX and X (vitamin K dependent clotting factors) for functional clotting activity.

Answer 63

vitamin K is required by factors II (prothrombin), VII, IX and X (vitamin K dependent clotting factors) for functional clotting activity.

Answer 64

Rodenticides are divided into first and second-generation compounds - the latter being developed as resistance to the first-generation products had developed in the wild rodent population

Answer 65

The second-generation rodenticides include compounds such as brodifacoum, bromadiolone and difenacoum.

Answer 66

The signs are caused by spontaneous haemorrhage, usually within two to five days of ingestion. As this is a disorder of secondary haemostasis, there may be clinical signs relating to ➢ bleeding into body cavities e.g. the pleural space, the pericardium, abdomen, joints ➢ pulmonary haemorrhage ➢ GI tract haemorrhage ➢ external bleeding from orifices (nasal cavity, oral cavity), wounds etc. ➢ intracranial or intraspinal cord haemorrhage

Answer 67

Clinical signs will include varying degrees of lethargy, weakness and anaemia. Additionally, depending on the location of the bleeding, clinical signs can include  bruising, haematomas  dyspnoea due to pleural space disease (see Unit 3 Outcome 2)  coughing, haemoptysis  abdominal distension  joint swelling/ lameness  pericardial effusion- muffled heart sounds (see Unit 3 Outcome 1)  seizures, paresis, paralysis

Answer 68

Disseminated intravascular coagulation (DIC) is a complicated derangement of the clotting pathways that arises secondary to some other serious problem. It often arises in association with systemic inflammatory response syndrome (SIRS)/ sepsis but can develop secondary to serious conditions e.g. trauma, heatstroke, pancreatitis. Widespread inflammation results in systemic coagulation- a hypercoagulable state. This leads to a prothrombotic state and the formation of multiple intravascular clots (microthrombi) that ultimately lead to reduced organ perfusion- being a further complicating factor in organ failure. Due to the prothrombotic state and formation of many intravascular clots, the clotting factors are consumed or ‘used-up’- this then leads to a clotting factor deficiency making the patient hypocoagulable (coagulopathic) with a tendency to bleed. In all cases, there will be clinical signs associated with the underlying disease process that has caused the systemic inflammation and DIC (e.g. pancreatitis, IMHA, sepsis). DIC may be present but be asymptomatic whereas some patients will have very serious signs with overt/ clinical bleeding

Answer 69

The diagnosis of DIC can be challenging especially in the early stages where it is subclinical (Hackner and Rousseau, 2015)- as it is a dynamic condition the signs and findings change frequently. There is also no specific diagnostic test for DIC- patients with clinical signs attributable to DIC often have thrombocytopaenia and prolonged clotting times (PT, aPTT) (Goggs and Hackner, 2018). Schistocytes may be apparent on a blood smear. One of the first indicators of a patient developing DIC, alongside clinical signs, is platelet consumption - so serial blood smears monitoring platelet numbers in patients at risk should be performed. The prognosis for patients that develop DIC is poor- early identification is essential to improve survival rates. It is essential in a patient with suspected or confirmed DIC to identify the underlying reason and treat it.

Answer 70

Other possible causes of acquired disorders of secondary haemostasis (coagulopathy) include liver failure (clotting factors are made in the liver) and dilution coagulopathy e.g. when larger volumes of fluids are given. In a patient with acute blood loss, platelets and clotting factors will be consumed. If the patient also receives intravenous fluid therapy (likely with hypovolaemia), all clotting factors (including von Willebrand’s factor) and platelets will be diluted. This can result in prolonged bleeding in some patients. Acquired coagulopathy can develop secondary to severe hypothermia. In human medicine the triad of death is reported and is certainly a concern in animal patients also.

Answer 71

These vary from patient to patient, the underlying cause, the location and the rate of blood loss. Depending on the underlying cause, blood loss can be acute or chronic. With acute blood loss, there will be signs of hypovolaemia e.g. pale mucous membranes, tachycardia, prolonged capillary refill time etc. A patient with chronic haemorrhage (e.g. endo/ectoparasites) may not show clinical signs until their iron store is significantly depleted. As young animals have less of an iron store, they may show clinical signs relatively earlier in the disease process. Patients can develop organ dysfunction (e.g. kidney) secondary to decreased perfusion due to hypovolaemia or microthrombi (hypercoagulable state). Diagnostic testing It is important to identify whether the bleeding is localised e.g. gastric ulcer or widespread e.g. coagulopathy

Answer 72

PCV Whole blood loss will influence blood composition and the PCV and TP/TS. How exactly it is affected depends on how recent the blood loss was. During active bleeding, whole blood is being lost (RBC, plasma proteins and plasma). At this stage, the actual PCV will not necessarily alter very much (Jasani, 2015) although the total blood volume will be decreased. Once compensatory mechanisms start to take an effect, fluid moves from the interstitial space into the bloodstream- meaning the remaining RBC and proteins will be diluted (so the PCV and TP/TS will decrease). In dogs, the spleen often contracts in response to haemorrhage meaning the PCV may remain in the normal range temporarily- the TP/TS, however, will still be reduced at this stage. This splenic response tends not to occur in cats. If there is ongoing, recurrent bleeding then the PCV will decrease.

Answer 73

If an abdominal or thoracic bleed is suspected, comparing the PCV of peripheral blood with the abdominal/thoracic blood can indicate whether there is active, current bleeding or whether it has occurred previously. If there is current haemorrhage, the PCV of peripheral blood and the thoracic/ abdominal sample will be very similar. If the haemorrhage occurred previously, the peripheral PCV could be higher, the same or less than the sample obtained by abdominocentesis or thoracocentesis. The fluid obtained from abdominocentesis/ thoracentesis will not clot as the clotting factors will have already been consumed at the time of the haemorrhage. If blood obtained doing ‘centesis does clot, it suggests accidental penetration of an organ/ blood vessel.

Answer 74

Abdominocentesis/ thoracentesis would not be appropriate in a patient with marked thrombocytopaenia or coagulopathy- therefore, before performing, a blood smear should be prepared, and an estimate made of the platelet count. If thrombocytopaenia/coagulopathy is suspected, blood samples should always be taken from peripheral veins and pressure applied for at least 5 minutes post-sampling.

Answer 75

With haemorrhage, usually the blood smear picture is a regenerative one with polychromasia, macrocytosis and an increased number of reticulocytes.

Answer 76

In cases associated with neoplasia, particularly haemangiosarcoma, or disseminated intravascular coagulation (DIC), fragments of red cells may be seen in the circulation these are known as schistocytes

Answer 77

As platelets/ thrombocytes are integral to haemostasis, thrombocytopaenia may be the underlying cause of haemorrhage; however, thrombocytopaenia could also arise secondary to platelet consumption during severe haemorrhage

Answer 78

Several fields (~10) are examined in the monolayer segment of the smear under oil immersion. The monolayer segment lies between the main body of the smear and the feathered edge- it is composed of a single layer of cells.

Answer 79

Each one platelet seen in an oil immersion (x100) | field is roughly equivalent to a platelet count of 15x109platelets/L.

Answer 80

Therefore, a normal blood smear should have ~ 11-15 platelets per field (x 100) - equating to a platelet count of 165- 225 x109platelets/L

Answer 81

Consistently (over several fields), less than 0-3 platelets per oil immersion field equates to a very dangerously low platelet count (equivalent to 0-45x109/L) Patients with < 5 platelets per field should be closely monitored for evidence of active haemorrhage.

Answer 82

Very large platelets suggest thrombopoiesis e.g. a bone marrow response.

Answer 83

Certain breeds of dog can have inherited macrothrombocytopaenia due to a mutation. This is common in Cavalier King Charles Spaniels, Norfolk and Cairn terriers amongst others

Answer 84

A true platelet count may be done, manually, using a haemocytometer, commercial diluting fluid and a microscope. A commercial ammonium oxalate diluent pipette system should be used e.g. ‘Unopette Micro-Collection System for WBC and Platelet Determination’ (BD Diagnostics, 2008). This is filled as directed and lyses the red cells after 10 minutes or so. A Neubauer modified haemocytometer is then filled with the mixture and left in a humid environment (a small covered dish with a layer of wet filter paper in the bottom) for 5-10 minutes, to allow the platelets to settle to the floor of the haemocytometer. A platelet count is performed by examining the haemocytometer microscopically. Platelets can be differentiated from white cells by their smaller size and refractile nature. The total number of platelets, in the central major square on each side of the haemocytometer, is counted. This square is divided into 25 smaller squares, each of which contains 16 further squares. The average of the two major square counts is then the total platelet count in 109/L. Normal values for dogs are 200-700x109/L and for cats are 300-800 x109/L

Answer 85

Abdominocentesis If abdominal bleeding is suspected, the abdomen may be examined using ultrasound (POCUS) - anechoic free fluid would be present. A peritoneal tap (abdominocentesis) should be performed to confirm the presence of the blood, unless coagulopathy/thrombocytopaenia is suspected/known. Blood that has been present in the abdomen for some time will not clot due to the clotting factors already having been used. As previously discussed, blood from a haemoabdomen may have the same PCV, lower PCV or higher PCV than the peripheral PCV depending on how chronic the condition is

Answer 86

Process Checked Screening Test What Test Evaluates

Answer 87

Primary Haemostasis Platelet Count Platelet numbers

Answer 88

Primary Haemostasis Buccal Mucosal Bleeding Time (BMBT) Platelet numbers and function; endothelial function

Answer 89

Primary Haemostasis Platelet Function Analyser (PFA- 100) ** Platelet function

Answer 90

Primary Haemostasis Platelet Aggregometry ** Platelet function

Answer 91

Primary Haemostasis Thromboelastography (TEG) and thromboelastometry (ROTEM) ** Platelet numbers and function, coagulation factors, haematocrit

Answer 92

Secondary Haemostasis Fibrinogen Fibrinogen concentration

Answer 93

Secondary Haemostasis Prothrombin time Factors VII:TF, X, V, II and fibrinogen

Answer 94

Secondary Haemostasis Activated partial thromboplastin time (aPTT) Factors XII, XI, IX, VIII, X, V, II and fibrinogen

Answer 95

Secondary Haemostasis Activated clotting time (ACT) Factors XII, XI, IX, VIII, X, V, II and fibrinogen

Answer 96

Secondary Haemostasis Thrombin time (TT) ** Fibrinogen concentration and quality

Answer 97

Fibrinolysis D-dimers Lysis of cross-linked fibrin

Answer 98

Fibrinolysis Tissue plasminogen activator, TEG and ROTEM ** Endogenous fibrinolytic potential

Answer 99

The main test that is used to determine if there is an abnormality of primary haemostasis is the buccal mucosal bleeding time (BMBT).

Answer 100

Buccal mucosal bleeding time (BMBT) - The BMBT uses a commercial device to produce two standardised cuts to the buccal mucosa of the upper lip - 5mm long and 1mm deep. Cats may need sedation for this test. The patient is placed in lateral recumbency, the upper lip reflected, to expose the mucosal surface, and held in place by a gauze tape lightly applied around the maxilla (BSAVA, 2010) (Oakley, 2007). The BMBT device is then placed on the mucosa and activated. The incisions are then left alone until bleeding stops- the time taken should be recorded. This is assessed by using a swab or filter paper placed near to the incisions (3-4 mm below), but not touching them- bleeding is judged to have stopped when blood stops being taken up by the clean edge of the swab/filter paper. The BMBT is taken as the mean bleeding time of the two incisions and should normally be less than 4 minutes (1.7- 3.3. minutes dogs and 1.0- 2.4 minutes in cats (BSAVA, 2010).

Answer 101

The BMBT evaluates primary haemostasis by assessing platelet and vascular aspects of haemostasis

Answer 102

``` Instances where BMBT may be prolonged include: • thrombocytopaenia • thrombopathia • blood vessel anomalies • von Willebrand’s disease • drug therapy e.g. aspirin ```

Answer 103

A BMBT should NOT be performed on patients that are already known to be thrombocytopaenic- thrombocytopaenia should be confirmed on a blood smear, as previously discussed. Thrombocytopaenic animals will have a prolonged BMBT so confirmation with the test is unnecessary.

Answer 104

Activated partial thromboplastin time (aPTT) assesses the function of both the intrinsic and common pathways.

Answer 105

Factors XII, XI, IX and VIII (intrinsic pathway) are evaluated by assessing aPTT; factor V, factor X, prothrombin (II) and/or fibrinogen (I) (common pathway) are also evaluated by assessing aPTT

Answer 106

This is not a very sensitive test, as, at least, one factor must be reduced to less than 30% of their normal values before aPTT. A dog with bleeding caused by haemophilia A, (lack of factor VIII) or von Willebrand’s disease, may have a prolonged aPTT but it is possible that it could still be within the normal reference range. aPTT is more sensitive to heparin and DIC

Answer 107

Prothrombin time (PT)- this identifies deficiencies in the extrinsic (factor VII:TF) and common pathways (fibrinogen (I), prothrombin (II), V and X).

Answer 108

It measures the time for fibrin to be produced after activation of factor VII. As with aPTT, at least one factor must be decreased by more than 30% for PT to be prolonged. Factor VII has the shortest half-life of the clotting factors, so PT maybe increased before aPTT in a patient with a coagulopathy. Vitamin K is required to activate factors II, VII, IX and X which are produced in the liver. Acquired vitamin K deficiency (rodenticide poisoning) is an example of a condition that can prolong PT (due to lack of active factor VII). Because of factor VII’s relatively short half-life, PT may be the only clotting test to be prolonged in the early stages of vitamin K deficiency, so PT is very sensitive to vitamin K deficiency. In rodenticide toxicity PT will be elevated first - however both aPTT and PT are likely to be prolonged over time. PT may also be prolonged due to DIC, chronic liver disease or endotoxaemia. The deficiency of factor VII will prolong PT even if there is no change in other clotting tests.

Answer 109

Point of care coagulometers are now available, from a variety of companies, which can be used in practice to evaluate aPTT and PT (N.B. this link demonstrates the use of one such coagulometer). They are very useful for in-house rapid results, especially when evaluating the intrinsic and common pathways. However, as they are not 100% sensitive and specific, any results that do not fit with clinical findings should be confirmed via conventional laboratory testing . It is very important that the samples are collected and stored, and analysers are used according to the manufacturer instructions. Some require a sample to be placed in sodium citrate; others involve taking a sample from the patient and placing directly in the analyser. For reliable information about coagulation, the sampling technique needs to be considered – a clean stick is needed, the sample should not be haemolysed and it should be handled carefully once obtained.

Answer 110

Activated clotting time. This is another point of care, in-house test-kit that can be used to measure activated clotting time (ACT) on a non-coagulated whole blood sample. It is a simple rapid test which identifies serious abnormalities in the intrinsic and common pathways. 2ml of blood is placed into a tube, warmed to 37°C, containing a contact activator e.g. diatomaceous earth. After careful mixing, the tube is gently tilted, at 10 second intervals, to determine if a clot has formed. Normal ACT for dogs is 60-110 seconds and for cats is 50-75 seconds.

Answer 111

Normal ACT for dogs is 60-110 seconds and for cats is 50-75 seconds.

Answer 112

D-dimers – these are fibrin degradation products (FDPs) that are created when a fibrin clot is broken down by plasmin. They are a sensitive test for DIC

Answer 113

A patient with serious blood loss will have signs of hypovolaemia/ hypovolaemic shock. Vascular access should be gained, preferably via the peripheral cephalic vein, in case of an underlying coagulopathy. Blood samples should be obtained at this stage, prior to starting treatment, for PCV, TS and blood smear evaluation initially; additional haematological, biochemical and clotting evaluation may be performed once the patient is more stable. As these patients may already have significant blood loss, care needs to be taken, especially in small patients, not to worsen the anaemia. If the patient is clearly coagulopathic at presentation, it may be sensible to take all the samples required at one time to prevent further venepuncture being required. This will be the decision of the attending veterinary surgeon. If possible, further blood loss should be prevented e.g. pressure on bleeding wound. Additionally, depending on the volume and rate of blood loss, crystalloid fluids or colloids may be required. Rarely, hypertonic saline (HTS) may be used. However, it should be noted that if the patient is bleeding uncontrollably e.g. into a cavity such as the abdomen, the increase in blood pressure and cardiovascular volume from HTS administration is likely to increase the blood loss. If the animal is severely anaemic or the PCV has dropped rapidly, a whole blood transfusion may be required. For animals who are bleeding due to deficiencies in coagulation factors (e.g. secondary to anticoagulant rodenticide intoxication), fresh frozen plasma, frozen plasma or packed RBCs may be administered. (PBBUK, 2020) If there is no access to processed blood products then a whole blood transfusion may be required. For feline patients in the UK, there is no access to a UK based feline blood bank with blood products meaning the only option for those patients is a whole blood transfusion. Oxygen supplementation may be required in some cases

Answer 114

The patient should be cage rested with minimal handling- deep bedding should be provided to prevent injury, including padding on the front of the kennel if they are likely to rub their face/nose or try to escape. Excessive venepuncture and other invasive techniques should be avoided to minimise further haemorrhage and effective haemostasis should be performed (pressure should be applied for a full five minutes). Jugular venepuncture should not be performed in patients with known or suspected abnormalities in primary or secondary haemostasis; and subcutaneous injections should be avoided. The patient should be observed closely for any deterioration/ complications e.g. ongoing/further haemorrhage, neurological signs, dyspnoea etc. Positioning of patients with suspected abdominal masses for procedures must be performed with extreme care to prevent inducing further haemorrhage -ideally the patient will be allowed to adopt the position they are most comfortable in. If haemorrhage into the pleural space is suspected to be the cause of dyspnoea, thoracocentesis may be required, depending on the patient’s clotting ability (for technique see Unit 3 Outcome 2). Pericardiocentesis may be required for the patient with cardiac tamponade due to haemopericardium (also dependent on clotting ability)

Answer 115

If abdominal haemorrhage is present, a pressure abdominal wrap may be applied if considered appropriate, in some cases. Additionally, with abdominal haemorrhage, if fresh blood is not available, auto-transfusion is a treatment possible option, the abdominal blood is collected and auto-transfused back into the patient’s circulation. As the clotting factors will already have been used, this will not correct any clotting deficiencies. It may, however, be enough to stabilise the patient whilst the underlying problem is corrected, or additional blood products are sourced. Autotransfusion should be performed through a blood giving set with a microfilter to remove any clots

Answer 116

Rodenticide poisoning In the case of rodenticide associated haemorrhage, or where rodenticide is suspected of being absorbed, vitamin K treatment will be required. It should be noted that it is no longer recommended to routinely start prophylactic vitamin K treatment as soon as ingestion of an anticoagulant rodenticide is confirmed (VPIS,2020). Recommendations are like other intoxications - including gastric decontamination, supportive therapy as needed and checking a baseline clotting profile (PT and APTT). The clotting profile is then checked every 24hrs for abnormalities – PT will become elevated first at which point Vitamin K therapy can begin if necessary The actual treatment regime depends on the type of rodenticide ingested and the results of blood tests to assess clotting function (see Unit 5, outcome 3). However, it will take at least 12 hours for new clotting factors to be produced by the patient, therefore a plasma transfusion may be required initially to provide an emergency supply of these. If the patient is anaemic, then packed RBCs may be administered as well; or a whole blood transfusion may be performed. The half-life of clotting factors is short so a second plasma transfusion may be required. Lower doses of vitamin K1 and a shorter course of treatment will be needed for patients with known first-generation rodenticide toxicity (BSAVA, 2020). Vitamin K1 is administered initially by subcutaneous injection (there is a risk of anaphylaxis with intravenous injection). The subcutaneous injection sites should be alternated and the patient’s activity restricted during this period to prevent the chance of bleeding (BSAVA, 2020). Modern, second generation rodenticides, such as brodifacoum, have prolonged halflives, remaining active in the body for a relatively long period- thus a longer course of vitamin K1 therapy may be needed – up to 3-4 weeks in most cases).Whilst parenteral vitamin K1 is used for the initial treatment, oral vitamin K can be administered for the remainder of the treatment. A final prothrombin time (PT) should be assessed 2-3 days after the last planned treatment. If the PT is prolonged, another 2 weeks of vitamin K1 therapy is indicated. Following this PT should again be performed 2-3 days after the last vitamin K1 treatment

Answer 117

Ongoing nursing care for patients with blood loss Once blood loss has been stopped and volume replacers administered as required, ongoing assessment of the patient’s vital signs should be instigated. This should focus on perfusion parameters- MM colour, CRT, heart rate, pulse quality and patient mentation. In addition, blood pressure and PCV should be monitored closely to identify any ongoing blood loss as quickly as possible. Clinical examination should include monitoring of the patient for development of DIC- in particular the patient should be monitored for signs of ecchymoses, petechiation, prolonged haemorrhage from venepuncture and/or haematuria. Bruising may develop especially on the ventral abdomen in some patients - clipping small patches of hair to be able to visualise that can be helpful. Clear nursing orders are required e.g. if the patient is thrombocytopaenic, it is therefore prone to spontaneous haemorrhage. Additional tests, such as aPTT and PT, may also be required to assess response to treatment, where clotting deficiencies are suspected.

Answer 118

Non-regenerative anaemia | This is when there is a reduced or failure of erythropoiesis in the bone marrow.

Answer 119

Possible aetiologies Non-regenerative anaemia could be associated with any of the following ➢ Bone marrow suppression or dysfunction associated with drug therapy e.g. chemotherapy, oestrogen, sulpha drugs, chloramphenicol and phenylbutazone ➢ Chronic organ failure (e.g. kidney disease- the kidneys are responsible for producing erythropoietin, a hormone which stimulates red cell production (erythropoiesis) and release from the bone marrow) ➢ Infection e.g. FeLV, FIV and Ehrlichia canis are possible causes. ➢ Myelodysplasia or aplasia of the bone marrow ➢ Neoplasia of the bone marrow or metastatic infiltration of the bone marrow by neoplastic cells - myelophthisis ➢ Lead poisoning ➢ Malabsorption or nutritional deficiencies e.g. iron or vitamin B12 may be a cause of non-regenerative anaemia. ➢ Chronic disease- anaemia of chronic disease is a very common cause of nonregenerative anaemia e.g. chronic inflammation, neoplasia, endocrinopathy etc.

Answer 120

Haematology Typically, there is no or minimal evidence of regeneration. The anaemia will usually be normocytic and normochromic. If it is associated with iron loss, then it may be microcytic and hypochromic. Reticulocytes will not be present with non-regenerative anaemia. However, with acute blood loss (haemorrhage / haemolyis), it can take 2-4 days for there to be a bone marrow response and evidence of regeneration. It is increasingly recognised that marrow-directed immunemediated disease exists, sometimes in conjunction with peripheral IMHA. In these cases, there may be no evidence of regeneration. Immunosuppressive therapy is often needed for weeks to months before the animal’s bone marrow becomes regenerative once again.

Answer 121

Anaemia associated with chronic renal failure tends to be relatively mild - whereas it will be severe in leukaemia induced aplastic anaemia. A concurrent leucopaenia and thrombocytopaenia (pancytopaenia) may be seen with some bone marrow conditions. Identification of the underlying cause of the non-regenerative anaemia is required- e.g. underlying kidney disease or endocrinopathy. Bone marrow biopsy may be indicated although this is not likely to be an emergency investigation. The prognosis for non-regenerative anaemia is often poorer due to the, often, serious nature of the underlying cause e.g. neoplastic infiltration of the bone marrow. The clinical findings will depend on the degree of the anaemia and how rapidly it has developed. Often non-regenerative anaemia develops slowly as RBCs have a relatively long lifespan (Fry, 2011). Clinical findings may be more related to the underlying condition e.g. polyuria/polydipsia with hyperadrenocorticism.

Answer 122

Like patients with regenerative anaemia, the focus is on supporting the cardiovascular system and maintaining an effective circulation of oxygenated blood. There is unlikely to be volume depletion (i.e. it is normovolaemic) but a packed red blood cell transfusion may be required to increase oxygen carrying capacity. A patient with chronic anaemia will have had time to adjust to the anaemia, and so the urgency for transfusion is usually less than with acute blood loss. Having chronically adjusted to the low haematocrit, the patient may be extremely anaemic on presentation e.g. PCV <15%.

Answer 123

Whole blood, packed red blood cells, plasma, and different subgroups of plasma may be administered to patients for different reasons.

Answer 124

Because of the necessary short time- scale from collection to administration to ensure the viability of platelets and some clotting factors (PBBUK, 2020) whole blood transfusions must be from in-house donors. Feline patients will need a fresh whole blood transfusion from a local donor in most scenarios. However, it is now possible to import feline blood into the UK for use in veterinary clinics.

Answer 125

Canine Fresh Whole Blood (FWB) contains red blood cells, platelets, leucocytes and all plasma proteins including the labile and nonlabile clotting factors. Not refrigerated and administered within 4-8 hours

Answer 126

Whole blood loss, platelet deficiency, no access to blood components e.g. packed RBCs

Answer 127

Whole blood that is > 8 hours since collection and is refrigerated at 1-6˚C for 21-28 days. Contains red blood cells, leucocytes, plasma proteins and non-labile clotting factors.

Answer 128

Anaemia and hypoproteinaemia N.B. separate pRBC and plasma transfusions may be a better treatment option

Answer 129

Packed red blood cells in nutrient solution. Restore oxygen carrying capacity. Refrigerated at 1-6˚C. The maximum length of storage depends on whether any additives are added to the RBCs (21- 42 days). Ideally pRBCs should be administered as soon after collection as possible due to potential issues associated with older pRBC administration

Answer 130

Anaemia with no loss of blood volume- lack of red blood cells only not clotting factors/ platelets

Answer 131

Plasma which is separated from whole blood and frozen within 24 hrs of collection. Previously guidance suggested it had to be separated and frozen to -18˚C within 8 hours of collection. Contains plasma proteins including all clotting factors. Must be used with 12 months or becomes frozen plasma. Source of all clotting factors, lipids, electrolytes, immunoglobulins and albumin

Answer 132

All clotting factor deficiencies coagulopathies; pretreatment of patients with von Willebrand’s disease; volume resuscitation acute trauma N.B. due to the high volumes required not indicated for hypoalbuminaemia

Answer 133

FFP that is greater than 12 months old; or thawed but unused FFP Does NOT contain clotting factor V, factor VIII or von Willebrand’s factor but does contain all the Vitamin K dependant clotting factors II, VII, IX, and X. Also source of lipids, electrolytes, immunoglobulins and albumin

Answer 134

Anticoagulant toxicities N.B. due to the high volumes required not indicated for hypoalbuminaemia

Answer 135

Portion of plasma which is separated from fresh frozen plasma by process of controlled thawing and centrifugation. It is a concentrated product containing the labile clotting factors. It contains fibrinogen, clotting factors VIII, von Willebrand’s Factor and fibrinogen. Once prepared, refrozen (< -18˚C) and stored for up to 1 year from original collection.

Answer 136

Source of factor VIII, fibrinogen and von Willebrand’s. NOT for inherited clotting factor deficiencies (II, VII, IX and X)

Answer 137

Separated from frozen plasma. Like FP containing non-labile clotting factors. This is what is left after cryoprecipitate has been removed. It does NOT contain factors VII, VIIIc, XIII and von Willebrand’s factor but does contain plasma proteins including albumin and Vitamin K dependant clotting factors II, VII, IX and X. Once prepared, refrozen (< -18˚C) and stored for up to 1 year from original collection

Answer 138

Vitamin K clotting factor deficiencies (II, Vii, IX | and X) NOT Haemophilia A and von Willebrand’s

Answer 139

Prepared from fresh whole blood. Very difficult to make as platelets so fragile and must be handled with extreme care (therefore fresh whole blood may be administered instead where platelets are required) (Gibson and Callan, 2018) Platelet rich plasma/ Platelet concentrate and Lyophilised platelets are currently unavailable in the UK

Answer 140

Severe uncontrollable haemorrhage due to thrombocytopaenia?

Answer 141

Indications for transfusion include- 1. anaemia- due to blood loss (regenerative- haemorrhage, haemolysis) or failure of production (non-regenerative) 2. coagulopathy 3. thrombocytopaenia

Answer 142

If a patient has anaemia, the decision to transfuse is based upon the patient’s clinical signs- NOT the value of the PCV. A feline patient with chronic renal failure, for example, could have a very low PCV of 15-20% due to decreased erythropoietin production. Because it is likely to be compensating well, there is minimal indication to administer a blood transfusion. A patient with acute blood loss from trauma, for example, may have a higher PCV of 25-30%. However, because they will be cardiovascularly unstable, hypoxic and hypotensive. transfusion is more likely to be required. Trigger points for deciding when to transfuse are non-specific - the decision to transfuse is made based on the patient’s clinical status, reason for the anaemia and response to supportive treatment.

Answer 143

The choice of product can be aided by assessing the patient’s PCV and total protein/ total solids (TP/TS).

Answer 144

If the PCV is low but the TP/TS is normal, the patient would benefit from a packed red blood cell transfusion

Answer 145

If both the PCV and TP/TS are both low, the patient would benefit from whole blood

Answer 146

If a patient has a coagulopathy, it would benefit from plasma and packed red blood cells if anaemia is present

Answer 147

Packed red blood cell transfusions are indicated for patients showing signs of low tissue oxygenation (hypoxia) as a result of the anaemia

Answer 148

The aim is NOT to return the PCV back to normal but to remove some of the clinical signs and hope that the bone marrow will respond, if possible.

Answer 149

In acute blood loss due to haemorrhage or haemolysis, a patient may show clinical signs due to low oxygen carrying capacity before their PCV has declined significantly, as discussed previously. In more chronic anaemia in dogs, clinical signs are not often apparent until the PCV is < 20%. However, for rapid, dramatic blood loss, serious clinical signs may be apparent, requiring life-saving transfusion, even if the dog’s PCV is above 20%. In a cat, a transfusion is not likely to be performed unless the PCV has decreased to 10-15% (International Cat Care, 2015). In any patient, if the PCV is < 12-15% there will be tissue hypoxia

Answer 150

``` Clinical signs that would prompt consideration of a blood transfusion in a normovolaemic patient include: • collapse • very depressed mentation • tachycardia • tachypnoea/ respiratory distress ```

Answer 151

Plasma products can be used for several reasons e.g. coagulopathy may be treated with plasma when there is active bleeding; or an invasive procedure is planned (e.g. surgery) in a patient with a known/ inherited coagulopathy e.g. Von Willebrand’s disease.

Answer 152

Although transfusions of plasma have previously been used in the management of hypoproteinaemia, this is no longer routinely recommended (Cotter, 2019) due to the large volumes that are necessary (e.g. 4 litres of plasma to correct hypoalbuminaemia in a 20kg dog) and the associated cost. In addition, transfusions are not benign- they can induce reactions and will affect the immune system. However, depending on the underlying cause for a hypoproteinaemia, a plasma transfusion may still be helpful in some patients. If there is capillary bed damage, for example, plasma products will provide labile clotting factors and help repair the endothelial glycocalyx so preventing further loss of proteins and therefore supporting oncotic pressure.

Answer 153

The ideal, in-house, cat donor should be larger than > 4-4.5kg and but not obese, to ensure enough blood volume can be taken; ideally it should be friendly and good-natured. Cats that are stressed by visits to the vet are not good donors- they are not choosing to donate so it is important that they are not unduly stressed by the procedure. Cats will require sedation to donate blood and the owner must be fully aware of any potential risks. The cat should be older than 12 -18 months but less than 8 years of age (ideally less than 5 years). Ideally, they should be indoor cats, that have not been outside of the UK, to avoid the risk of transmitting any infectious diseases, including those screened for. Cats with current disease (e.g. renal, hepatic, abscess etc.) or those on medication should not be used. The donor should also be up to date with vaccinations and worming. The donor cat should not have received a blood transfusion previously. Pregnant queens should not be used due to the risks imposed on the mother and unborn foetuses. However, previously pregnant but currently non-pregnant queens can be used as donors. Cats should not give blood more than once every 3 months. It is essential to consider donor welfare – this should be paramount to the decision making for these patients. There is no benefit to the donor of this procedure, especially as there is a need for sedation with most feline donors. Consequently everything possible must be done to protect the welfare of the donor - including making the decision that they are not suitable to donate.

Answer 154

The ideal, in-house, cat donor should be larger than > 4-4.5kg (International Cat Care, 2018) (Tappin, 2016) and (PBBUK, 2020) but not obese, to ensure enough blood volume can be taken

Answer 155

The cat should be older than 12 -18 months but less than 8 years of age (ideally less than 5 years)

Answer 156

Cats should not give blood more than once every 3 months.

Answer 157

A full clinical examination should be performed- ideally this includes echocardiography to exclude occult heart disease. The donor’s blood pressure should also be measured before donation and assessed as being within the normal range (~ 120 mmHg -180 mmHg) The donor’s biochemistry and haematology should be checked and screened for feline viruses (FeLV, FIV) and ideally Mycoplasma (Haemobartonella) haemofelis infection prior to giving blood. Ideally cats would also be screened for FIP but this is problematic as many healthy cats possess antibodies to Feline Coronavirus. If an outdoor cat is used, infectious diseases should be screened for on each occasion. The PCV of the donor should be established, prior to donation, to ensure it is within the normal range- it should be > 30% and ideally > 35%. TS should be confirmed at the same time. It is essential that blood typing is performed too.

Answer 158

The blood type is determined by the presence of specific antigens on the surface of the erythrocytes. These antigens stimulate an immune response, with production of antibodies, in a cat of a different blood type. This can trigger an immune-system response (transfusion reaction) in the recipient, resulting in haemolysis of the donated erythrocytes.

Answer 159

Cats are either type A (most in the UK), type B, or very occasionally AB

Answer 160

most non-pedigree cats are type A

Answer 161

many pedigree cats are type B

Answer 162

Cats have naturally occurring antibodies to the other blood type i.e. a type A cat will have antibodies to type B RBC antigens. Because of this, there is no universal donor in cats- most cats develop naturally occurring antibodies in the first few months of life to other blood types (unlike dogs and humans). cross matching should be considered even when carrying out a feline blood transfusion for the first time. Type AB cats do not have antibodies

Answer 163

Type B cats have high levels of anti-A antibodies (95% have antibodies).

Answer 164

Type B cats should NOT receive blood from either group A or group AB recipients otherwise a very severe major transfusion reaction would occur.

Answer 165

If a type B cat is given type A blood, a very serious transfusion reaction is likely to occur when anti-A antibodies haemolyse type A RBC - this could be rapidly fatal

Answer 166

Type A cats will generally have antibodies to type B RBC antigens but at a low level (titre)

Answer 167

In type A cats, transfused with type B blood, the transfusion reaction is likely to be less serious but the transfused RBC will be very short-lived

Answer 168

A type AB patient should ideally receive type AB blood although it is often hard to find AB donors. They could possibly receive type A blood as there are relatively low levels of anti-B antibodies in this. There will, however, probably be some transfusion reaction. Type A packed RBC or washed type A RBCs would be ideal but these cannot currently be produced in general practice. Type B donors should NOT be used due to the high levels of anti-A antibodies.

Answer 169

The half-life of transfused erythrocytes in the correctly typed and cross matched feline recipient is about 30-38 days.

Answer 170

If incorrectly matched, this can be much shorter (matter of hours in the case of A erythrocytes transfused into a B type cat; or 1-2 days in the case of B erythrocytes transfused into an A type cat).

Answer 171

There is also a rare, recently identified, Mik antigen (cats) that cannot be screened for by typing. Pre-existing anti- Mik antibodies are present in some cats however the prevalence of these are not known. As discussed later, cross matching should be considered even when carrying out a feline blood transfusion for the first time.

Answer 172

EDTA blood samples can be submitted to external laboratories for typing e.g. University of Glasgow (n.d.) or University of Bristol (n.d.). Commercial, simple rapid card-agglutination tests can be used in- house • Rapid Vet-H Feline, DMS Laboratories (Rapidvet Company, 2012) • Feline Quick Test , Alice Veterinary Diagnostic

Answer 173

Blood typing of both the donor and recipient is necessary

Answer 174

Cross matching is an in vitro test (Walton, 2015) where donor and recipient blood is mixed to look for signs of a potential reaction. In cats, the reaction could be agglutination or haemolysis

Answer 175

In cats, the reaction could be agglutination or haemolysis

Answer 176

It is important to cross matchcross match before performing a transfusion in a cat, especially if the blood types are not known or the recipient has previously received a transfusion - as it will have developed new antibodies to the transfused blood. The recently identified Mik antigen, means that it is even more important that cats are cross matched – the Mik antigen was first identified after a cat had a transfusion reaction following administration of typed, compatible A blood.

Answer 177

Cross matching can be performed by a commercial laboratory or can be performed in-house.

Answer 178

There are commercial gel tests for performing rapid in-house cross matching . Agglutinated/ clumped RBC are unable to pass through the gel matrix- thus in a positive cross matchcross match RBCs remain at the top and in a negative cross match they pass through. However, because incompatibility in cats might present as haemolysis instead of agglutination, there may be difficulty in interpretation. In cats, therefore, the rapid slide test is generally used as a means of cross matching blood in an emergency. Because of the likelihood of there being antibodies present in cat blood to the other blood type, an abbreviated version of the full cross match procedure can be performed

Answer 179

The rapid slide test (abbreviated slide procedure) is performed as follows- 1. A blood sample is taken from the donor and the recipient 2. Some blood from each cat is placed into labelled plain tubes and allowed to clot; blood from each cat is also placed into labelled potassium EDTA tubes 3. All tubes (potassium EDTA and plain) are centrifuged to separate the blood cells from plasma /serum. 4. Four clean glass slides are prepared and labelled as follows- a. Donor control b. Major cross match c. Minor cross match d. Recipient control 5. On the donor control slide, one drop of donor erythrocytes (from the spun down potassium EDTA tube) is added to two drops of donor serum or plasma (ideally serum should be used for the cross match). 6. On the major cross match slide, one drop of donor erythrocytes (from the spun down potassium EDTA tube) is added to two drops of recipient serum or plasma. 7. On the minor cross match slide, one drop of recipient erythrocytes (from the spun down potassium EDTA tube) is added to two drops of donor serum or plasma. 8. On the recipient control slide, one drop of recipient erythrocytes (from the spun down potassium EDTA tube) is added to two drops of recipient serum or plasma. 9. The slides should be carefully rocked back and forwards. Within 2 minutes of mixing, the slides should be examined for visual evidence of macroscopic agglutination reactions; within 5 -15 minutes of mixing, examine each slide should be examined microscopically for evidence of microscopic agglutination The same rapid slide test that is used for cats may be used for cross matching dog blood

Answer 180

agglutination (clumping of erythrocytes)

Answer 181

It is important to differentiate agglutination (clumping of erythrocytes) from rouleaux formation (organised stacking erythrocytes on top of another). Agglutination suggests there has been a cross match reaction but rouleaux formation does not. This differentiation can only be made microscopically as demonstrated at pattern changes

Answer 182

The major cross match tests for antibodies in the recipient’s serum/plasma against donor RBCs. An incompatible MAJOR cross match would show that a serious, acute, haemolytic transfusion reaction would arise if the transfusion was performed.

Answer 183

The minor cross match tests for antibodies in the donor’s serum/plasma against recipient RBCs. An incompatible MINOR cross match is less likely to cause a transfusion reaction due to the volume of donor plasma being small and dilution in the recipient

Answer 184

The following results of the cross match slide test could arise- ➢ Type A serum mixed with type B or AB erythrocytes would result in a weak, macroscopic agglutination (visible to the naked eye) or no agglutination at all. ➢ Type B serum mixed with type A or AB erythrocytes would usually result in a strong macroscopic agglutination reaction. ➢ Type AB serum mixed with type A or type B erythrocytes should result in no reaction.

Answer 185

Type A serum mixed with type B or AB erythrocytes would result in a weak, macroscopic agglutination (visible to the naked eye) or no agglutination at all.

Answer 186

Type B serum mixed with type A or AB erythrocytes would usually result in a strong macroscopic agglutination reaction.

Answer 187

➢ Type AB serum mixed with type A or type B erythrocytes should result in no reaction.

Answer 188

A positive major cross match (strong agglutination) suggests type B has been the recipient and type A or AB has been the donor.

Answer 189

A positive minor cross match slide test (strong agglutination) suggests type A or AB as the recipient and type B as the donor.

Answer 190

To differentiate between a type A and a type AB donor, the minor cross match slide should be examined. There will be little or no agglutination in the case of the type A donor and no agglutination with the type AB donor.

Answer 191

If the major and minor cross matches are both negative (no agglutination) then the donor and recipient are likely to be the same blood type.

Answer 192

Cross matching can also be done by mixing samples in tubes (International Cat Care, 2015) but this is more time-consuming. The procedure is similar but after the initial centrifugation, the plasma should be removed from the EDTA tubes and the RBCs washed in 2-3 mls of saline. They should be centrifuged again and the saline removed. This should be repeated twice. The RBCs should be suspended in saline- 0.2 ml RBC to 4.8 ml saline. 4 tubes are labelled and mixed as for the slide test (donor control, major cross match, minor cross match and recipient control). The tubes are now incubated at 37°C for 15 minutes before being centrifuged and analysed. The samples can be analysed macroscopically and microscopically as above

Answer 193

Interpretation of the cross match slide test can be done as follows- ➢ To differentiate between a type A and a type AB donor, the minor cross match slide should be examined. There will be little or no agglutination in the case of the type A donor and no agglutination with the type AB donor. ➢ To differentiate between the two, examine the major cross match test. If the recipient is type A, there will be no reaction or it will be weakly positive; if the recipient is type AB, there will be no reaction. ➢ If the major and minor cross matches are both negative (no agglutination) then the donor and recipient are likely to be the same blood type.

Answer 194

Occasionally, even though the results are negative (no agglutination), there may be low levels of anti-B or anti-A antibodies. This may result in mild haemolysis occurring sometime after the transfusion. Agglutination in the donor or recipient controls, is usually due to operator error. It is important to be aware that despite blood typing and cross matching, a transfusion reaction could still occur. Consequently, all recipients should be monitored very closely during and following the blood transfusion

Answer 195

As with cats, the larger the dog, and the more placid it is, the easier and more suitable a donor it will make. The dog should be health screened to ensure it is free of disease. It should weigh more than 25kg in weight, be in good body condition and aged between 12 months (PBBUK, 2020) and 18 months and 7-8 years of age. The donor should be up to date with preventative healthcare (vaccination, worming and some sources also advise regular flea treatment); although none should have been administered recently (within 2 weeks for vaccinations). To avoid transmission of some infectious diseases, not present in the UK, the dog must not have travelled abroad (PBBUK, 2020). A potential donor should not have had recent surgery, be pregnant or received a previous blood transfusion (it may have developed alloantibodies against a transfused, different blood type). A dog can donate every one to three months as required. A dog should not need to be sedated for donation – sedation is not allowed for dogs donating to an authorised blood bank

Answer 196

It should weigh more than 25kg in weight

Answer 197

aged between 12 months and 18 months and 7-8 years of age

Answer 198

A dog can donate every one to three months as required

Answer 199

As a minimum requirement, the donor’s PCV and TS should be checked prior to donation to ensure they are within normal limits. Ideally a full haematological and biochemical assessment should be also performed. The donor should ideally be screened for conditions such as pathogens such as Babesia sp., Brucella canis, Haemobartonella canis and Dirofilaria immitis (heartworm). Whilst there are very few vector spread, blood-borne conditions endemic in the UK (Gibson and Callan, 2018), there have been recent reports of dogs affected with Babesiosis who have not travelled abroad. It may be that more comprehensive screening for blood -borne pathogens will be introduced in the future. Increasing incidence of Angiostrongylus vasorum in dogs in the UK is a consideration prior to donation. One potential complication of A. vasorum infection is a coagulopathy which would be a risk to the donor (Gibson and Callan, 2018). Point of care antigen tests to detect A. vasorum infection may be considered in areas where infection level is high.

Answer 200

A pregnant bitch should not be used owing to the risk to her and the foetuses. Tappin (2016) discusses the potential risk of a bitch who has had a previous pregnancy being used as a donor. There is the possibility that a DEA 1.1 negative bitch bred with a DEA 1.1 positive dog may have developed DEA1.1 antibodies thus increasing the risk of her blood causing a minor transfusion reaction in the recipient; although another study found no incidence of pregnancy related alloantibody formation

Answer 201

classified according to the surface antigens (dog erythrocyte antigen - DEA)

Answer 202

Unlike cats, dogs do not have naturally occurring alloantibodies to the different blood antigens. It is rare, therefore, for a reaction to occur immediately the first time a patient is transfused with non-compatible blood

Answer 203

Most of the blood groups are not of significance when considering blood transfusions as they are not very antigenic

Answer 204

DEA 1 is the most immunogenic antigen therefore it is most likely to stimulate antibody production after a transfusion to a noncompatible recipient

Answer 205

Contrary to what was previously considered, it is important to appreciate that there is no universal canine donor blood type. Consequently, it is considered best practice to blood type and cross match all donor and recipient blood for dogs, as with cats, irrespective of whether there has been a previous transfusion or not

Answer 206

``` Most of the blood groups are not of significance when considering blood transfusions as they are not very antigenic. The DEA 1 status of the donor is, however, clinically very important for compatibility screening. DEA 1 is the most immunogenic antigen therefore it is most likely to stimulate antibody production after a transfusion to a noncompatible recipient). Transfusion of incompatible RBCs will cause an immune reaction. If a DEA 1 negative dog receives blood from a DEA 1 positive one, it takes some time (> 4days post-transfusion) for antibodies to form in the recipient (DEA1 negative). A haemolytic reaction is therefore likely to be delayed and can occur 1-2 weeks after the transfusion. This is often mild, with no/ minimal clinical signs (Yagi, 2016). Once antibodies have formed, however, the recipient will react much more quickly to any further DEA1 positive blood being transfused. Preexisting antibodies against DEA 1, following a previous non-compatible transfusion, can cause potentially a fatal, haemolytic transfusion reaction within a few hours of administration ```

Answer 207

the concept of a ‘free first transfusion’ in a dog is a myth. As previously discussed, if a mismatched transfusion occurs (e.g. DEA 1 negative dog receives DEA 1 positive blood), there will be a delayed haemolytic reaction, often mild although possibly with anaemia and bilirubinuria. The dog’s immune system is now sensitised, and any further mismatched transfusion would cause an immediate and dramatic transfusion reaction. This is a particular concern in patients that require repeated transfusions such as those with IMHA. If it is known that the dog has had a previous transfusion, this significant potential problem can be recognised in advance

Answer 208

If the dog has moved to a new home or been rescued and it has no medical history, there is a significant risk if it requires a blood transfusion but had previously had one. If there is any doubt as to whether a previous transfusion has been administered, cross matching should be performed

Answer 209

Ideally a donor dog would be negative for DEA1, 2, 3, 5 and 7. The most important DEA to be negative to is DEA 1 as it is most antigenic

Answer 210

Ideally, DEA1 negative dogs should receive DEA 1 negative blood

Answer 211

DEA 1 positive dogs could receive DEA1 positive or negative blood

Answer 212

This means if it is genuinely not possible to | perform typing of a recipient for a first transfusion only, then DEA 1 negative blood products should be used

Answer 213

In the UK, it is currently only possible to routinely test for DEA 1, when typing, - the other DEA antigens cannot be identified. If blood typing cannot be performed immediately, a sample of both donor and recipient blood should be tested later in case a further transfusion is required

Answer 214

~ 60% of canine blood bank donors, when | blood-typed, were DEA 1 negative

Answer 215

- ~ 78% of Greyhounds tested were DEA 1 negative Many Boxer and Flat Coat Retriever donors are also DEA 1 negative;

Answer 216

Golden Retrievers and all Rottweiler donors are DEA 1 positive

Answer 217

Test cards are currently available for DEA1 determination- • Rapid Vet-H (Rapid Vet Company, 2012) • Canine Quick Test

Answer 218

As with cats it is best practice to cross match all dogs and it is a misconception that blood type testing for DEA 1 means cross matching in dogs is unnecessary. There are many possible causes of blood incompatibility especially as there are so many DEA groups and the likelihood of, yet, unrecognised groups

Answer 219

As discussed previously, cross matching is particularly important if - • the recipient received blood more than 4 days previously and a second transfusion is anticipated • The recipient has had a previous transfusion reaction • The recipient has been pregnant previously • The previous history of the patient is unknown.

Answer 220

The commercial, in-house gel tests can be used for dogs and are rapid and relatively easy to interpret demonstrating both major and minor cross matches

Answer 221

Where time allows, the test tube test is recommended

Answer 222

The procedure for performing the test tube test is described 1. Blood samples are collected as for the slide test 2. Then spun down in a centrifuge. Washed erythrocytes from both the donor and recipient are made into a 4% solution by taking 0.2ml of spun down erythrocytes from the potassium EDTA sample and adding this to 4.8ml of isotonic saline - this helps to prevent rouleaux formation 3. Four tubes are labelled as for the four slides in the rapid slide test a. Donor control b. Major cross match c. Minor cross match d. Recipient control 4. Into each tube, 2 drops of the 4% red cell solution and 2 drops of serum/plasma is added as described below (N.B. serum is preferred) a. Donor control tube- two drops of donor erythrocyte suspension is added to two drops of donor serum (or plasma). b. Major cross match tube- two drops of donor erythrocyte suspension are added to two drops of recipient serum (or plasma). c. Minor cross match tube- two drops of recipient erythrocyte suspension are added to two drops of donor serum (or plasma). d. Recipient control tube- two drops of recipient erythrocyte suspension is added to two drops of recipient serum (or plasma). 5. The tubes are then lightly centrifuged at low speed for 20-30 seconds to encourage the red cells to accumulate. 6. The tubes are gently shaken and held up to the light to examine for evidence of macroscopic agglutination or haemolysis. 7. If ‘clots’ are apparent macroscopically, the sample should be examined microscopically to determine whether they are true ‘clots’ (agglutination) or nonspecific rouleaux formation. 8. The degree of clotting/cross reaction can then be graded from a. No clots microscopically or macroscopically (negative) b. Microscopic aggregates (+w) c. Small macroscopic aggregates (+1) d. Medium macroscopic aggregates (+2) e. Several large macroscopic aggregates (+3) f. One large clot (+4) The results can be interpreted as follows1. A positive major cross match suggests the recipient has many antibodies to the donor erythrocytes. This suggests that the recipient has anti-DEA1 antibodies and, therefore, this donor’s blood would NOT be suitable for the recipient. 2. A positive minor cross match suggests that the donor has antibodies against the recipient’s erythrocytes. The strongest reactions occur in the presence of anti-DEA1 antibodies meaning that donor’s plasma should NOT be used for this recipient. The donor’s erythrocytes could potentially be used, providing they are washed in saline before administration. This, however, is rarely possible in practice. 3. A positive recipient control suggests that the recipient’s blood is autoagglutinating. This is likely to be caused by non-specific anti-erythrocyte antibodies rather than specific DEA ones. 4. A positive donor control usually suggests a handling error or, rarely, that the donor could have immune mediated haemolytic anaemia

Answer 223

The degree of clotting/cross reaction can then be graded from a. No clots microscopically or macroscopically (negative) b. Microscopic aggregates (+w) c. Small macroscopic aggregates (+1) d. Medium macroscopic aggregates (+2) e. Several large macroscopic aggregates (+3) f. One large clot (+4)

Answer 224

A positive major cross match suggests the recipient has many antibodies to the donor erythrocytes. This suggests that the recipient has anti-DEA1 antibodies and, therefore, this donor’s blood would NOT be suitable for the recipient

Answer 225

A positive minor cross match suggests that the donor has antibodies against the recipient’s erythrocytes. The strongest reactions occur in the presence of anti-DEA1 antibodies meaning that donor’s plasma should NOT be used for this recipient. The donor’s erythrocytes could potentially be used, providing they are washed in saline before administration. This, however, is rarely possible in practice.

Answer 226

A positive recipient control suggests that the recipient’s blood is autoagglutinating. This is likely to be caused by non-specific anti-erythrocyte antibodies rather than specific DEA ones.

Answer 227

A positive donor control usually suggests a handling error or, rarely, that the donor could have immune mediated hemolytic

Answer 228

A closed collection system is where the only exposure of the blood collection equipment to air is when the cap is removed from the needle prior to venepuncture thus limiting the potential for contamination.

Answer 229

Blood collected using an open system should ideally be administered immediately. If being stored it should be refrigerated between 1-6 ˚C and used within 24 hours of collection.

Answer 230

The following equipment is required for collecting blood from a feline donor 1. Sedation/ anaesthesia drugs and equipment 2. Clippers 3. Diluted chlorhexidine (or povidone-iodine) 4. Cotton wool/ gauze swabs/gloves 6. 250ml or 450ml blood collection bag as source of CPDA-1/CPD. 7. Sterile 10ml syringe and 20G needle to withdraw anticoagulant 8. 60ml luer tip syringe, 19G butterfly catheter and three-way tap 9. 2 or 3 small swabs 5cm roll conforming bandage i.e. vet wrap for neck bandage 10. Scissors 11. +/- Plastic or guarded haemostat (protective cover over haemostat teeth) 12. +/- Macroclamp-P 13. Neck bandage equipment

Answer 231

For closed blood collection in the dog the following equipment is required 1. Clippers 2. Diluted chlorhexidine/ povidine-iodine solution 3. Cotton wool/ gauze swabs/gloves 4. Surgical spirit 5. 450 ml blood collection bag with CPDA-1 or CPD anticoagulant 6. Plastic or guarded haemostat (protective cover over haemostat teeth) 7. +/- Macoclamp-P if using (used to seal and prevent contamination) 8. +/- Tube stripper 9. Scissors 10. Electronic scales for weighing blood if using a collection bag 11. Swabs and bandage material for neck bandage after the collection

Answer 232

Needle The needle should be placed in the jugular vein to allow a rapid bleed with minimal risk of coagulation. It is important to get a clean first ‘stick’ to limit the chance of clot formation and limit loss of platelets. Flow should be consistent if the needle is well seated in the vessel. It is possible for the donor to develop a haematoma during this process so careful monitoring of the venepuncture site during collection is necessary. Sometimes the haematoma will be significant meaning that the donation will need to be stopped. The bag is connected to a length of drip tubing which is connected to 16- gauge thin walled needle.

Answer 233

60ml Syringe This can be used for collecting blood in cats. It should be pre-filled with the correct volume of anticoagulant (CPDA1 or CPD) from a blood collection bag prior to use. Smaller syringes filled with proportionately less anticoagulant can be also be used.

Answer 234

The blood collection bag that is used as source of anticoagulant for feline blood collection can be used for administering the blood transfusion if required. The remaining anticoagulant must first be removed and discarded.

Answer 235

These are generally supplied as a 450ml capacity bag containing 63ml of citrate phosphate dextrose adenine1 (CPDA1) or citrate phosphate dextrose (CPD) as anticoagulant

Answer 236

If the intention is to separate the blood into plasma and packed red cells, then ‘triple’ or ‘quad’ bags are available. These have satellite bags for separation of the products. Small animal single and double bag syringe collection sets are also available

Answer 237

The best anti-coagulant used for storing blood for any length of time is citrate based either citrate phosphate dextrose adenine1 (CPDA1) or citrate phosphate dextrose (CPD)

Answer 238

The ratio of anticoagulant to blood should be ~ 1:7.

Answer 239

Blood collection bags contain ~ 63 ml of anticoagulant per 450 ml bag

Answer 240

There is too much anticoagulant in a 250 ml/ 450 ml blood collection bag for the amount of blood that can be collected from a small animal e.g. a cat. Therefore, for a cat blood collection, 7.5ml of anticoagulant is withdrawn aseptically from the collection bag initially. This is then introduced, using a three-way tap, into the 60ml syringe that is to be used for the collecting the blood- meaning that the ratio of blood to anticoagulant will be correct. Whilst commercial cat collection bags are available, they are not routinely used in the UK

Answer 241

For collecting erythrocytes only (i.e. separating blood post collection), the anticoagulant used should be citrate phosphate dextrose adenine1 (CPDA1). If no other anticoagulant is available, it is possible to use heparin if an immediate transfusion is planned although this is not ideal

Answer 242

Whole blood should ideally be administered as soon as possible, after collection, for various reasons- blood that was collected over four to eight hours previously, is no longer considered ‘fresh’. As previously discussed, there is a progressive loss of labile clotting factors and platelets. Additionally, the level of compounds such as 2,3 diphosphoglycerate (2,3-DPG) in the blood decreases proportionately to the time stored with time stored. This compound increases the binding of haemoglobin to oxygen and decreased levels can be particularly significant in dogs

Answer 243

Cats and dogs can donate ~ 20% of their blood volume - maximum 11 ml/kg (cat) and maximum 18ml/kg (dog)

Answer 244

maximum 11 ml/kg (cat)

Answer 245

maximum 18ml/kg (dog)

Answer 246

a full unit (450 ml bag) of blood is collected.

Answer 247

Generally, 2ml of transfused whole blood/kg of the recipient’s weight raises the recipient’s PCV by 1%.

Answer 248

1ml of transfused packed red blood cells/kg of the recipient’s weight raises the recipient’s PCV by 1%

Answer 249

To calculate the required blood volume more precisely the following formula can be used- ❖ Volume of donor blood (ml) = 80(dog) x BW (kg) x desired change PCV/PCV of transfused blood ➢ N.B. BW is the body weight of the recipient. ➢ N.B. for cats, the factor in the equation above is 60 as their blood volume is lower than dogs

Answer 250

A more recent formula which is thought to accurately estimate the new PCV following transfusion is- ❖ PCV change (%) = volume administered (bodyweight (kg) x 1.5)

Answer 251

Plasma products may be administered at 4-6 ml/kg/hr with a total dose of 10-20ml/kg per day

Answer 252

A cat’s blood volume is ~ 60 ml/kg (55-65 ml/kg)-

Answer 253

Collection technique (feline) It is essential that an aseptic technique is used throughout with very close attention to infection control. Prior to commencing the volume of blood to be collected should be calculated. A cat’s blood volume is ~ 60 ml/kg (55-65 ml/kg)- no more than 20% of the cat’s blood volume should be collected (< 11-13 ml/kg). If the volume that the recipient requires has been pre-calculated, that is all that should be taken from the donor to reduce the risk. The correct amount of anticoagulant for the volume of blood required should be introduced into the 60-ml syringe attached to a butterfly catheter using an aseptic technique- 1ml anticoagulant to 7 ml blood or 1.3 ml anticoagulant to 10 ml blood (PBBUK, 2020). If the bag is to be used for administering the blood, the remaining anticoagulant should be removed at this stage. The catheter tubing should be charged with anticoagulant and the guarded haemostat positioned (PBBUK, 2020). N.B. It is essential that air does not enter the collection system.

Answer 254

Sedation / anaesthesia Sedation is generally required for cats as it takes several minutes to collect the blood from the jugular vein. Most cats will not sit still for long enough to allow for this and sedation/ general anaesthesia will limit stress. Butorphanol and diazepam combination; or ketamine and midazolam/diazepam combinations. Alternatively, full anaesthesia can be induced with an IV induction agent e.g. propofol and maintained with isoflurane/sevoflurane and oxygen (PBBUK, 2020) and (Tappin, 2016). Alpha 2 agonists should be avoided. However, it could be argued that if a full general anaesthesia is required to immobilise the patient adequately, they are not a suitable donor

Answer 255

Venepuncture and blood collection Once the cat is sedated or anaesthetised the jugular region should be clipped (5 cm x 5 cm) and surgically prepared. EMLA cream can be applied. The cat is positioned in lateral recumbency with the forelimbs drawn caudally to aid visualisation of the vein. If the cat is only lightly sedated, sternal recumbency is another option (PBBUK, 2020). The phlebotomist applies new sterile gloves and introduces the primed 19-gauge winged (butterfly) catheter, attached to a 60ml syringe, aseptically into the cat’s jugular vein which is raised by the assistant. The haemostat is removed from the tubing and gentle pressure is applied to the syringe to create a gentle vacuum – excessive pressure will stop the blood flow and collapse the vessel especially if using a 60ml syringe system. (PBBUK, 2020). If the technique is correct, blood should flow freely into the syringe at a rate of ~ 5ml/minute. The syringe should be rocked gently as the blood is being collected to ensure mixing of blood with anticoagulant. If smaller syringes are used, these are attached in turn to the three-way tap. Once the calculated volume has been collected (~ 57 ml), the three-way tap is turned off towards the donor and the assistant stops raising the vein. The needle is removed from the vein and immediately recapped, using a safe technique. Blood products should be clearly labelled including donor identification, date and time of collection. Blood type and other pertinent information should be recorded even if it is being administered immediately to the recipient.

Answer 256

Aftercare of the donor The assistant should apply direct pressure to the donor’s vein, using swabs, for at least two minutes and possibly up to 5 minutes. Thereafter a Vetrap™ bandage is applied over the swabs and kept on for 30-60 minutes. The donor should be closely observed during this period with monitoring of heart rate, blood pressure and mucous membrane colour. Cats should be offered food and kept quietly cage rested for the first 3-4 hours postdonation. Intravenous fluids may be administered at 30 ml/kg over three hours although this is not routinely recommended by all sources (Gibson and Callan, 2018). They should be kept indoors for the next 24-48 hours if they go outdoors. The blood can be administered to the recipient immediately following collection - the butterfly needle and tubing are removed from the three-way tap. It can either be administered directly from the syringe through a Hemo-nate filter or it can be introduced into a plain blood bag (anticoagulant removed) and administered through a filtered giving set.

Answer 257

Restraint Most dogs will not require sedation or anaesthesia, but instead can be restrained preferably in lateral recumbency. If it is considered that sedation is needed, then the choice of dog choice as a donor should be reviewed. At Pet Blood Bank UK (PBBUK) donation sessions, for example, the dog is lifted onto a padded table and placed in lateral recumbency. Light restraint is used – the dog is stroked and reassured to ensure it settles and is relaxed for the procedure. The dog is never held down or forced to remain in position.

Answer 258

Venepuncture and blood collection Using an aseptic technique, the blood collection bag is removed from its protective wrapper and placed on the scales which are then zeroed. A haemostat is applied to the tubing. If blood products are to be stored, a closed collection must be used (Walton, 2014). The jugular vein is clipped and prepared aseptically in advance; EMLA cream should be applied and allowed time to work. Ideally the dog is placed in lateral recumbency with forelimbs drawn caudally. The needle of the collection bag is introduced into the jugular vein with a clean ‘stick’ to minimise the risk of platelet loss and clot formation. The needle should be well sited into the vein to ensure it does not become dislodged during the collection process. The assistant should remove the haemostat and blood should start to flow freely. With a flow rate of 40-50 ml/ minute the collection should be complete within 15 minutes. The collection bag should be rocked gently, every 50 ml or 15 seconds, as blood is collected to ensure mixing with the anticoagulant. Once the bag starts to become quite full it is important to pay attention to its weight. The maximum amount which can be safely collected from a dog is 16-18m/kg. Generally, however, one unit (450ml) (~ 405-495 ml) is collected from an appropriately sized donor. Each 1ml of blood weighs 1.053 g so the weight of the bag is ~ 426 – 521g (Gibson and Callan, 2018). Once the bag is sufficiently full, pressure is relieved from the jugular vein and the tubing re-clamped. A tubing stripper can be used to milk the blood from the tubing into the bag. The tubing can then be clamped at 10 cm intervals for later cross matching. The blood collection bag should be clearly labelled for identification purposes with patient identification, date, expiry date and blood type (Gibson and Callan, 2018). After the needle is removed from the vein direct pressure is applied to the jugular vein, using swabs, for at least two minutes to prevent haematoma formation. A Vetrap™ bandage is applied over the swabs and kept in place for 30-60 minutes.

Answer 259

Aftercare of the donor The donor’s demeanour and vital signs (heart rate, mucous membrane colour and pulse quality) should be checked every 10-15 minutes initially. The patient should be offered water and a little food. The donor should be kept quiet for the following evening and night and only very lightly lead exercised for the following 24-72 hours. A harness is preferred to a collar to avoid pressure on the jugular vein. Dogs generally do not require intravenous fluids following donation but monitoring for signs of hypotension is important.

Answer 260

The blood that has been collected is centrifuged at 3800 rpm for 15 minutes at 4C, in a dedicated purpose-built blood transfusion centrifuge, to separate RBC and plasma

Answer 261

Plasma is separated from RBC, using a manual plasma separator, and transferred into satellite bags. This yields two products that can be used for different recipients- packed red blood cells and fresh plasma- these can be further split meaning four recipients could benefit from one donation. Samples are taken from each product for typing and cross- matching. Availability of stored blood products allows the vet to tailor treatment according to the patient’s needs e.g. an anaemic patient may require red blood cells but not plasma; a patient with a coagulopathy will require the clotting factors found in plasma but not necessarily red blood cells, unless there has been a significant haemorrhage.

Answer 262

Plasma should be frozen to – 20 C or lower as soon as possible, but within 24 hours to retain all its properties. It can then be stored as fresh frozen plasma (FFP) for up to one year. After one year it can be relabelled as frozen plasma with a shelf life of 5years.

Answer 263

If plasma is frozen after 24 hours it becomes frozen plasma (FP) (NOT FRESH PLASMA) as it has reduced coagulation properties- it has a shelf life of five years

Answer 264

Packed red blood cells can be stored at 1-6 ˚C for up to 42 days- the addition of a nutrient solution (SAGM) within the collection system helps to preserve their life

Answer 265

Details of the expiry date of the blood product should also be recorded and each unit individually labelled detailing the blood type of the unit, the date of collection, the expiry date, the donor’s individual number/identifier, the PCV of the sample and the total protein and the type of sample (whole blood etc.) as well as the name of the clinician who was responsible for collecting the sample/unit

Answer 266

Legal requirements The date of collection and details of the donor should be recorded. Details of the expiry date of the blood product should also be recorded and each unit individually labelled detailing the blood type of the unit, the date of collection, the expiry date, the donor’s individual number/identifier, the PCV of the sample and the total protein and the type of sample (whole blood etc.) as well as the name of the clinician who was responsible for collecting the sample/unit. When blood products are administered, the date and recipient’s details must also be recorded. Transfusion records can be downloaded from the PBBUK website. Using a transfusion record ensures all pertinent patient information is recorded and can be attached to their clinical records

Answer 267

consent should be obtained prior to administration of blood products. As they are biological products, there is a potential risk associated with their administration even if appropriate typing, cross matching and storage has been performed. The owner should be aware that there is a risk of a transfusion reaction, despite careful preparation. Rarely, the reaction could be life-threatening e.g. sepsis or toxic reaction. N.B. Screening, typing and cross matching does not completely prevent the possibility of transmission of infectious agents or transfusion reactions

Answer 268

Transfusion technique The patient should not be fed or given any medication during the transfusion. Prior to starting the blood product should be checked for type, expiry date etc. It should be visually inspected for any evidence of discolouration or presence of clots- bacterial contamination causes a brown to purple change in colour of RBC containing products. An aseptic technique must be used throughout. The shorter and wider the IV or IO cannula, the more rapidly the product can be administered.

Answer 269

They have a very short lifespan once breached and should ideally be used within 4 hours of opening some sources state up to six or eight hours

Answer 270

Prior to transfusion, blood products should ideally be warmed to at least room temperature although the temperature MUST NOT exceed 37°C (Walton, 2014). Some authors, however, advise against active warming due to the potential for bacteraemia. Blood products can be gently and slowly warmed by placing them in a waterproof ziplock bag and placing this in a temperature monitored water bath. Using a protective zip pack whilst warming prevents contamination of the ports. Neither whole blood nor blood products should ever be warmed in the microwave as this will cause damage It should be noted that as the initial transfusion rate is very low for the first 30 minutes, meaning the temperature of the blood product e.g. pRBCs will increase to room temperature during that time. Active warming must be done cautiously - however it is very rarely indicated. If whole blood has been recently removed from the donor for immediate transfusion or refrigerated briefly before administration, it will not need to be warmed, as it will come to room temperature quite quickly. For platelets to be functional, the fresh whole blood should be kept at room temperature and used within 4 hours of collection. If whole blood is being administered the bag should be gently inverted to mix the components prior to administration.

Answer 271

Fresh whole blood can be administered for anaemia associated with clinical signs e.g. blood loss

Answer 272

Whole blood is the only source of platelets | and labile coagulation factors

Answer 273

10 ml/kg of fresh blood is reported | to raise the platelet count by 10 x 109/l

Answer 274

Packed red cells can be administered instead of whole blood where the patient has anaemia without hypovolaemia and does not need clotting factors. Packed RBCs can also be used if there is a risk of volume overload.

Answer 275

Blood products are generally administered intravenously either via a peripheral vein or through a central (jugular) line. For collapsed, moribund patients where venous access is not possible, the intra-osseous route could be used.

Answer 276

For any product containing RBCs, a microfilter is required to prevent small, microthrombi entering the patient’s circulation (PBBUK, 2020) (Walton, 2015). Filters are already present in the giving sets of blood bags. If a standard giving set is being used, however, then a separate in-line filter (e.g. Hemo-Nate) is required. It should be noted that some filters e.g. Hemo-Nate filters require changing after a certain volume of blood has been administered through them. The patient should be checked before and monitored closely during and following the transfusion

Answer 277

To prevent clot formation, calcium containing products should NOT be used with blood products e.g. Lactated Ringer’s Solution. 0.9% saline can, however, be administered with blood products. Packed RBCs no longer need to be resuspended with saline prior to administration (PBBUK, 2020). Glucose should also not be administered through the same IV line as the transfusion. Once the transfusion is finished the cannula should be flushed with 0.9 % saline before administering any other IV products. Hypotonic solution should not be used as they cause haemolysis and as discussed previously products containing calcium e.g. LRS should be avoided (Proulx and Waddell, 2012). If intravenous fluids e.g. LRS are required following/during a transfusion, it is good to place a second intra-venous catheter if possible. This means one can be maintained for blood products and the other for fluids and other medications.

Answer 278

The initial rate of administration is generally relatively slow at ~ 0.25-1 ml/kg/hour for the first 15-30 minutes. This should ensure prompt, early recognition of an immediate transfusion reaction before too much blood has been administered.

Answer 279

After this initial slow rate, the rate of infusion is increased to allow the remainder to be administered within the next 2-3.5 hours- the transfusion should be completed within 4 hours ideally to decrease the risk of bacteraemia. The standard rate of administration is ~ 4-6 ml/kg/ hour (PBBUK, 2020). Higher rates may be required depending on the clinical circumstances- in an emergency RBCs can be given as rapidly as needed. For patients with heart or renal failure, a maximum of 2-3 ml/kg/hour is suggested (International Cat Care, 2017) checked before.

Answer 280

For small patients, cats and neonates, a syringe driver can be used to deliver the blood at the required rate. Yagi (2016) discusses recent research into the optimum method of delivery of blood products- some methods are associated with RBC damage and decreased survival. Current best practice, for larger volume transfusions with a relatively high flow rate is to use gravity flow if close monitoring is provided for consistency of blood flow (Yagi, 2016). Peristaltic type infusion pumps are not recommended for administering products containing RBCs unless the manufacturer has specifically stated they are safe for this use. Yagi (2016) explains that validation of infusion pump use for veterinary blood products would be advantageous. Jasani (2015) discusses this further in the podcast presentation on administration of blood

Answer 281

Blood typing should have been performed but cross matching is not required for plasma products unless previous transfusions have been performed

Answer 282

A significant advantage of plasma is that it can be frozen and so can be stored longer than whole blood. It is, however, brittle and could be damaged if not handled carefully. Frozen plasma products should be thawed carefully in a warmed, temperature controlled/ monitored water bath (PBBUK, 2020) at a temperature < 37C prior to usethey must NOT be defrosted in the microwave.

Answer 283

``` Fresh frozen plasma can be used to treat patients with deficiencies in coagulation factors of various causes e.g. anticoagulant rodenticide toxicity, liver disease, and hereditary coagulopathies (see 3.3.6). Frozen plasma does not contain labile clotting factors but can be used as a source of non-labile clotting factors (see 3.3.6) Plasma obviously does not contain erythrocytes, platelets or leucocytes and so is of no use in patients that require replacement of these three products. It is mainly used to replace depleted coagulation factors. As previously discussed, it is not recommended for treating hypoalbuminaemia due to the large volumes required ```

Answer 284

Plasma should be administered through a filter in case of any fibrin clots or other cell debris. As with RBC transfusions, filters are already present in the giving sets of blood bags- if a standard giving set is being used, however, then a separate in-line filter (e.g. Hemo-Nate) is required.

Answer 285

The initial rate of administration is generally relatively slow at ~ 0.5-1 ml/kg/hour for the first 15-30 minutes This should ensure prompt, early recognition of an immediate transfusion reaction before too much blood has been administered

Answer 286

After this initial slow rate, the rate of infusion is increased to allow the remainder to be administered within the next 3.5 hours- the transfusion should be completed within 4 hours ideally to decrease the risk of bacteraemia. The standard rate of administration is ~ 4-6 ml/kg/ hour

Answer 287

The dose is usually ~ 10 mL/kg, although the dose range is wide. Generally, however, the maximum volume to be infused is 12 ml/kg (Gibson and Callan, 2018) - 20ml/kg/hour (Walton, 2014) in normovolaemic patients. Larger volumes may be required to manage the coagulopathy of patients with rodenticide intoxication

Answer 288

Peristaltic type infusion pumps can be used for plasma if the manufacturer states this

Answer 289

The patient should be assessed prior to starting the transfusion- its clinical status will obviously be dependent on the underlying disease/ injury e.g. there may already be jaundice in a case of immune mediated haemolytic anaemia. Baseline recordings of vital parameters should be recorded e.g. rectal temperature, mucous membrane colour, CRT, heart/ pulse rate and rhythm, respiratory rate and pattern +/- urine colour if possible. Ideally blood pressure should be recorded prior to and during the transfusion. The patient’s demeanour should be noted too. Any change in the patient’s condition during the transfusion could possibly indicate a reaction so it is important to monitor closely and have something to compare to. At minimum PCV and TP/TS should be monitored before the transfusion, after completion and 12-24 hours later (Gibson and Callan, 2018). However as these are critically ill patients it may be monitored more frequently in conjunction with other parameters such as electrolyte and acid base status.

Answer 290

The patient should be monitored continuously for the first 30 minutes of the transfusion. Ideally the monitoring should be continuous for the duration of the transfusion but if this is not possible, checks should be made at least every 15-30 minutes

Answer 291

The signs most often associated with immediate transfusion reactions are pyrexia, altered respiratory and heart rate and GI signs e.g. vomiting. Change in mucous membrane colour and signs such as urticaria and oedema may also develop. Urticaria can suggest an acute hypersensitivity reaction

Answer 292

If a reaction occurs, a veterinary surgeon must be alerted immediately. If the signs are very mild, decreasing the rate of administration may be enough for the signs to subside but the patient must now be monitored continuously. If serious signs are present, the transfusion should be stopped immediately until the type of reaction is identified. Depending on the type of reaction present, it may be possible to continue with caution, drug therapy may be required, or the transfusion may have to be stopped at that stage.

Answer 293

It is also essential to monitor the patient closely for signs of over infusion especially if very small, young or if there is coexisting disease e.g. heart failure. Ongoing assessment of the patient’s demeanour and behaviour is important along with checking and recording vital signs. Any unusual behaviour e.g. unsettled/ shivering or clinical signs e.g. vomiting/ urticaria should be addressed immediately. Ideally ECG, blood pressure and temperature recording should be performed throughout

Answer 294

Problems with administration If the infusion stops or slows down, the patency of the IV cannula should be confirmed and the filter examined for evidence of air bubbles, clots or debris. If gravity infusion is being used, raising the bag may help. If the product appears viscous, careful administration of 0.9% saline may help. Regular checks on the patency of the catheter and assessment for signs of extravasation are indicated.

Answer 295

However, delayed reactions can also occur. Therefore, it is important to keep the patient under close observation for any clinical signs or behaviours which may indicate a possible transfusion reaction. However, delayed reactions can also occur. Therefore, it is important to keep the patient under close observation for any clinical signs or behaviours which may indicate a possible transfusion reaction. Blood pressure, temperature and ECG monitoring should be continued in the posttransfusion period.

Answer 296

``` Clinical signs to be aware of include 1. Tachycardia (although cats will occasionally show bradycardia) 2. Arrhythmia 3. Weak pulses 4. Tachypnoea 5. Dyspnoea 6. Pale mucous membranes 7. Weakness, lethargy, decreased mentation 8. Muscle tremors 9. Evidence of haemolysis e.g. jaundice, haemoglobinuria and haemoglobinaemia. 10.Pyrexia ```

Answer 297

If a patient has received RBCs, the PCV and TS should be checked 1-6 hours post transfusion

Answer 298

It is important not to check PCV/ TS too soon ‘as fluid compartment equilibrium may be incomplete, leading to inaccurately high PCV readings’

Answer 299

if there is no ongoing haemorrhage or haemolysis ‘70% of the transfused RBCs are expected to remain in circulation’. They further explain that if whole blood was transfused the RBCs should have the same lifespan as normal ~ 110 days in dogs and ~ 70 days in cats. The lifespan of packed RBCs is, however, shorter and affected by various factors e.g. age, storage etc.

Answer 300

The most common signs in dogs are pyrexia and vomiting. There was reported to be an increased incidence of transfusion reactions in dogs with immune-mediated disease. Dyspnoea would be considered a very serious sign in a patient receiving a transfusion as all those that died developed dyspnoea

Answer 301

Transfusion reactions are classed immunological or non-immunological

Answer 302

``` Hypersensitivity reaction (Type I and Type II) ``` RBC incompatibility- haemolytic. Acute and delayed (Type II) Febrile non-haemolytic reactionto WBCs/ platelets (Type I) Immunosuppression Post- transfusion purpurathrombocytopaenia Transfusion related acute lung injury (TRALI)

Answer 303

Infectious disease transmission Volume overload Hypothermia Citrate toxicity- citrate chelates calcium (hypocalcemia) Thrombosis Transfusion related acute lung injury (TRALI) Bacterial contamination- could lead to endotoxic shock, DIC and death. If suspected, stop transfusion and blood should be examined microscopically (grams stain) and cultured. Poor prognosis Storage issues- hyperammonaemia, hyperkalaemia, acidosis Dilutional coagulopathy if stored products which lack platelets and Factors V, VIII and IX are transfused. Non- immunological haemolysis - mechanical, infusion pumps, overheating, freezing RBCs (most should be noted prior to starting)

Answer 304

Consequently, there are four main types of reaction that could develop because of a transfusion 1. Acute immunological transfusion reaction 2. Delayed immunological transfusion reaction 3. Acute non-immunological transfusion reaction 4. Delayed non-immunological transfusion reaction

Answer 305

Hypersensitivity reactions are the result of an immune response to foreign antigens. A hypersensitivity response may develop on first exposure but is much more likely to arise on subsequent exposures once the immune system has been primed and is able to ‘remember’ previous exposure. Hypersensitivity reactions that might develop in response to blood products are Type I (allergic), Type II (cytotoxic) and Type III (immune complex)

Answer 306

Acute immunological transfusion reaction (Type II) This is the response that develops when foreign, genetically different RBCs are transfused into a patient. The antigen – antibody response results in intravascular and extravascular haemolysis i.e. destruction of the RBCs. This reaction should be avoided if compatibility testing is performed prior to transfusion.

Answer 307

The time that it takes for this reaction to develop depends on whether there are preexisting antibodies to these foreign RBCs. If there are pre-existing antibodies an acute haemolytic transfusion reaction will occur with rapid destruction of the transfused RBCs by the recipient’ s immune system. This could occur in any cat where blood typing has not been done or in a dog that has had a previous unmatched transfusion. If there are no pre-existing antibodies, a delayed haemolytic reaction will occur. The delay is the time taken for the immune system to develop a response to the foreign RBCs- e.g. a dog where compatibility testing has not been performed. Subsequent transfusions of the same blood would lead to an immediate transfusion reaction.

Answer 308

The severity of the reaction depends on the amount of the RBCs that have been transfused- hence the reason that transfusions should be started slowly. The most severe reaction will arise in a patient that has had a previous incompatible blood transfusion where there are pre-existing antibodies . This causes an acute haemolytic crisis with pyrexia, haemoglobinuria and haemoglobinaemia. The haemolytic response can stimulate intravascular coagulation leading to disseminated intravascular coagulation (DIC). The patient is likely to rapidly develop signs of shock with decreased perfusion and hypotension- cats may develop bradycardia. The most serious cases will be fatal.

Answer 309

A delayed haemolytic reaction is likely to arise 3-21 days post-transfusion depending on the speed of the immune response

Answer 310

This can range in severity from being asymptomatic to clinical signs of pyrexia, haemoglobinuria and jaundice. The most common sign associated with a delayed transfusion reaction is a sudden drop in PCV.

Answer 311

If an immediate type II reaction is suspected, the transfusion MUST be stopped immediately. Supportive treatment for shock will be required with IV fluids, vasopressors +/- inotropes. Glucocorticoids may be used to try to limit the immune response

Answer 312

Acute immunological transfusion reaction (Type I) A type I reaction is an allergic reaction and is mediated by immunoglobulin E (Yagi, 2016). The detection of a foreign antigen by IgE antibodies results in mast cell degranulation and the release of inflammatory mediators. The inflammatory mediators e.g. histamine, serotonin and prostaglandins cause an acute inflammatory response

Answer 313

The inflammatory mediators e.g. histamine, serotonin and prostaglandins cause an acute inflammatory responsewith clinical signs which can include vomiting, diarrhoea, pyrexia, urticaria / ‘hives’, pruritus and facial swelling. In the most serious cases, there may be an anaphylactic reaction. Dogs with anaphylaxis tend to show haemodynamic collapse with hypotension whereas cats tend to show signs of hypersalivation, dyspnoea, collapse. A halo sign around the gall bladder may be seen on ultrasound in a patient who is experiencing a anaphylactic reaction.

Answer 314

This ‘allergic’ type I hypersensitivity reaction can be caused by any blood product but is most likely to be caused by antigens on donor white blood cells, platelets and plasma proteins. Yagi also states that the risk of a type I reaction increases the longer RBCs have been stored. Clinical signs tend to develop very rapidly which is why is classed as an immediate hypersensitivity reaction. Affected cases are not usually pyrexic and they tend to respond to administration of antihistamines and corticosteroids unlike type II reactions.

Answer 315

Type III Hypersensitivity This can be caused by intravenous administration of antigens which then form complexes with antibodies. In dogs, it has been caused by administration of human serum albumin, tetanus antitoxin, snake antivenom and incompatible plasma transfusions (Yagi, 2016). The immune complexes can cause damage to blood vessels, kidneys, synovial membranes and blood cells.

Answer 316

Clinical signs vary but could include pyrexia, neutropaenia, anaemia, thrombocytopaenia, enlarge lymph nodes, lameness and joint swelling and proteinuria.

Answer 317

Clinical signs usually develop 1-3 weeks | following the transfusion. Treatment is symptomatic

Answer 318

TRALI This is a condition, mainly recognised in humans, where the patient develops acute onset dyspnoea with hypoxaemia and hypoxia within a few hours of the transfusion starting. The pathophysiology of the condition is not fully recognised and the incidence in small animal transfusion medicine is unknown.

Answer 319

non-immunological transfusion reaction Acute circulatory overload/ transfusion-associated circulatory overload (TACO) It results from too rapid a rate of blood transfusion especially in a normovolaemic patient. This causes signs of circulatory overload with coughing, tachypnoea, dyspnoea and tachycardia. In more serious cases cardiac abnormalities and pulmonary oedema or pleural effusion can develop.

Answer 320

an anaphylactoid type reaction can arise due to mast cell degranulation. This is not an immune response but is thought to be caused by too rapid administration of plasma proteins. The clinical signs, however, are the same as a type I hypersensitivity reaction with shock in the worst scenario.

Answer 321

Hypothermia is another potential side-effect from rapid administration of cold blood products, particularly in smaller patients/neonates.

Answer 322

non-immunological reaction Hypocalcaemic tetany may also occur due to chelation of blood calcium by the presence of large amounts of citrated blood products. This is due to anticoagulants containing citrate- however should be avoidable if the correct amount of anticoagulant is used for the volume of blood collected. Clinical signs of hypocalcaemia will be present including hyperaesthesia, muscle tremors, collapse, seizuring vomiting and cardiac arrhythmias. Ionised calcium levels will be lowered. This can be managed with calcium gluconate at 0.5-1.5ml/kg IV given slowly over 10 minutes.

Answer 323

Sepsis is a potential problem when using stored blood products- bacterial contamination of transfused products could lead to endotoxic shock, DIC and death. Signs usually develop 24-36 hours post transfusion (e.g. vomiting, diarrhoea, tachycardia, pyrexia, collapse, hypotension and haemolysis). The bacteria or fungi responsible are usually those that can survive in chilled storage such as Yersinia spp. and Pseudomonas spp. in the case of whole blood products. If bacterial contamination is suspected during the transfusion, it should be stopped immediately and the blood should be examined microscopically (grams stain) and cultured. The prognosis is poor for affected patients

Answer 324

Should a transfusion reaction take place, the following steps should be followed: 1. Stop the transfusion 2. Alert the veterinary surgeon 3. If necessary, start resuscitation procedures as described in Unit 1 Outcome 3 4. If the patient does not need resuscitation, record clinical parameters – TPR, mucous membrane colour, capillary refill time etc. 5. Auscultate chest – check for arrhythmias. Carry out ECG if possible 6. Measure blood pressure 7. Medical therapy may be required on veterinary direction e.g. antihistamine / corticosteroid therapy if urticaria or angioedema is present

Answer 325

****Oxyglobin is NOT currently available. *** Oxyglobin® is a polymerised bovine haemoglobin solution. It has previously been used where a blood transfusion is not possible, but the oxygen carrying capacity of the patient’s blood is compromised. It is easy to use and has very good penetrative powers through small or damaged capillary beds as the haemoglobin molecule is about 100 times smaller than the erythrocyte. It rarely causes any reactions during or after administration- although as it is an effective plasma expander, there is a risk of volume overload

Answer 326

It does however interfere with some biochemical tests and patients can develop haemoglobinaemia, haemoglobinuria and sometimes jaundice following administration.

Answer 327

It does not last very long with a half-life of 18-26 hours and a maximum duration of 82 hours- red cell transfusions should last ~ 4-6 weeks

Answer 328

Oxyglobin® dose rate is 10-30mg/kg with a maximum rate of administration of 10ml/kg/hour in dogs.

Answer 329

Oxyglobin® has significant oncotic potential and will act as a plasma volume expander. As it also causes vasoconstriction the patient’s blood pressure may increase- which may be beneficial or detrimental depending on whether the patient is hypovolaemic or not.

Answer 330

An auto-transfusion can be performed by collecting blood from the body cavity of a patient who has haemorrhaged and re-infusing it into the venous circulation.

Answer 331

this should not be performed in a patient suspected to have neoplasia (e.g. haemoabdomen from a ruptured splenic haemangiosarcoma)

Answer 332

Because the bloodalready likely to have been fibrinolysed within the body cavity (clots broken down) an anticoagulant is not necessary

Answer 333

An aseptic technique, however, is essential. Blood can be collected using a sterile technique either into a 60ml syringe or a regular blood transfusion bag and administered as discussed previously through a filter to remove any microthrombi and debris

Answer 334

This is the transfusion of blood from another species e.g. transfusion of canine blood to a feline patient. Cats are most likely to be considered for xenotransfusion due to the relative difficulty in obtaining appropriate feline blood, especially in an emergency. N.B. Xenotransfusion should be considered as a last resort option for those with life threatening haemorrhage or anaemia where there are absolutely no alternative options.

Answer 335

Factors which make ready access to feline blood challenging include- ➢ availability of donor cat with correct blood type ➢ pre-existing antibodies meaning there is no universal feline blood donor type ➢ requirement to sedate the donor ➢ volume of blood required ➢ limited access to, cost and time delay for stored feline blood products

Answer 336

The evidence suggests that cats do not have naturally occurring antibodies to canine red blood cell antigens. Additionally they report that compatibility tests prior to a xenotransfusion did not demonstrate haemolysis or agglutination; there have been no reports of a severe transfusion reaction in a cat receiving a one-off transfusion of whole canine blood; anaemic cats receiving canine blood are reported to show improvement within several hours of the transfusion.

Answer 337

However, the transfused red blood cells will not last long (average 4 days) as antibodies are generally produced within 4-7 days of transfusion resulting in a delayed, haemolytic transfusion reaction. Additionally, the evidence suggests that if the xenotransfusion is repeated, after 4 -6 days from the first transfusion have elapsed, a serious anaphylactic response is likely which is often fatal.

Answer 338

Indications for performing a xenotransfusion- specifically dog to cat transfusion a xenotransfusion should not be performed if allogenic blood products are available i.e. suitable feline whole blood or stored packed red blood cells (pRBCs) (currently in the UK stored blood products would have to be imported from Portugal). The most likely reason for performing a dog to cat transfusion is where the patient has life-threatening anaemia and no suitable feline product can be available in the required time scale.

Answer 339

• A xenotransfusion can only be performed ONCE in a patient’s lifetime. Cats will rapidly develop antibodies (within a few days) which cause haemolysis of the transfused blood. This means that should a second xenotransfusion be performed (after this), a fatal transfusion reaction could occur

Answer 340

Experimental work cited by Adamantos and Smith (2016) suggests that cross matching of the canine donor blood and feline recipient blood prior to transfusion is unlikely to a show major incompatibility reaction; however, a minor cross match incompatibility may be present. Euler et al. (2016) advise that there might be various incompatibilities between canine and feline blood and that cross matching is not likely to reliably predict a transfusion reaction

Answer 341

``` Anaemia- regenerative or non-regenerative Blood loss Coagulopathy DIC Thrombocytopaenia ( if blood fresh) ```

Answer 342

The correct answer is: 3 year old, 5kg, female neutered indoor cat

Answer 343

The correct answer is: All of the above

Answer 344

The correct answer is: There is no universal donor in cats

Answer 345

d. 200ml CorrectGenerally, 2ml of transfused whole blood/kg of the recipient’s weight raises the recipient’s PCV by 1%. and Volume of donor blood required (ml) = 80(dog) x BW (kg) x desired change PCV PCV of transfused blood

Answer 346

The correct answer is: Medetomidine / ketamine

Answer 347

``` Details of when the blood was collected The patient from which it was collected Blood type The details of the recipient The expiry date of the blood product The PCV of the sample ( if appropriate) Name of clinician responsible for collecting the sample/unit ```

Answer 348

``` Displacement Phlebitis Thrombosis Infection Catheter embolism Air embolism Exsanguination Bandage/ tape issues ```

Answer 349

The correct answer is: Brodifacoum

Answer 350

The correct answer is: Acute haemorrhage

Answer 351

The correct answer is: Erythropoietin