Blood groups and transfusion medicine Flashcards
What are blood groups based on?
Refer to inherited antigens on surface of the red blood cells
What does the degree of reaction to a transfusion depend on?
- Titre (amounts) of antibodies
- Isotype (IgM vs IgG)
- Antibody leading to either immediate lysis or graudal removal
What is the effect of an antibody that leads to the immediate lysis of red blood cells regarding transfusions?
Totally failed transfusion, likely death
What determines the nature and frequency of blood transfusion reactions?
Presence of naturally occurring antibodies to blood group antigens
Compare the risk of transfusion reaction between dogs and cats, and explain
- Dogs: few naturally occurring antibodies to major blood groups, low risk of transfusion reaction
- Cats often have naturally occurring antibodies to major blood groups, increases risk of transfusion reaction
Name the main blood groups in dogs
- > 10 blood group systems
- Dog Erythrocyte antigen: 6 types: 1.1, 1.2, (1.3), 3, 4, 5, 7 (alternate: 1,3, 4, 5, 7)
- Dal
- Kai
Discuss the importance of the Dal and Kai blood groups
- Usually delayed transfusion reactions
- Generally not typed for
Name the main blood groups of horses and identify the most immunogenic
- 7 groups
- A, C, D, K, P, Q, U
- Aa, Qa, Ca
Why are standard breed horses commonly used as blood donors?
Low prevalence of Aa and Qa
Describe blood transfusions from cattle
- Healthy donor, easy to handle, not heavily pregnant
- Cross matching unnecessary, transfusion reactions after single administration of blood are rare and mild
- Rare but consider in selected cases
Outline the principles of blood group testing
- Blood typing detects antigen pattern on erythrocyte surface
- Typing does not determine the presence of antibodies, i.e. does not mean totally compatible with donor
- Simple kits available for cats, dogs, horses
- Lab tests fo equine and bovine samples
Explain the principles of cross matching for blood transfusions
- If have had previous transfusions will have antibodies to blood types so type is irrelevant
- Assesses blood compatibility between donor and recipient
Compare a major and a minor cross match for blood transfusions
- Major: detects if recipient’s serum contains any antibodies against the donor’s RBCs
- Minor: detects if donor’s serum contains any antibodies against the recipient’s RBCs
Outline the method for cross matching of blood
- Collect sampples from donor and recipient into anticoagulant tube (EDTA/heparin)
- Centrifuse samples and remove and retain plasma
- Resuspend in saline, repeat centrifuge-discard 3 times to wash RBCs
- Prepare 3-5% washed RBC suspension with saline
- Major: mix donor RBC suspension with plasma from recipient (equal vol) and vice versa for minor
- Incubate at 37, 20 and 4°C
- Check after 15-30 mins for haemolysis and/or agglutination by visual inspection or microscopically
What is the ideal blood donor type for dogs and why?
DEA1.1 negative, as antibodies to DEA1.1 are responsible for acute reactions in dogs, but less crucial vs cats
Outline the requirement for blood typing and cross matching in dogs for blood transfusions
- Most dogs can receive first transfusion safely
- Type first, ideally cross match
- If cannot type, then transfusion should be fairly safe the first time
- IF gone beyond 4 days, are likely to have mounted immune response to antigens the animal has encountered before so definitely need to blood type
- Ideally second transfusion cross matched
What blood can be given to DEA 1.1 positive fogs?
Can receive DEA1.1 positive or negative
Outline the requirement for blood typing and cross matching in cats for blood transfusions
- Much greater risk in cats than dogs of peracute and fatal transfusions reactions
- Never transfuse without typing
Describe the reactions caused by type B feline blood type
Type B: high incidence of anti-A antibodies, leads to peracute reaction in A or AB cat
Which blood types can be given to which cats?
- AB donate to A or AB, not B
- AB can receive A or AB (low risk of anti-B antibodies in A may cause minor reaction)
- Only B blood to B cats, not AB due to anti-A antibodies in type B cats
What are the aims of blood transfusions?
- Replace what is lacking
- Support patient whilst investigations are carried out/treatment initiated
- Aim for clinical improvement rather than normal PCV (post transfusion PCV 25-30% in dogs, 20% in cats)
List the indications for the use of blood transfusions
- Evidence for circulatory collapse
- Rapid drop in PCV from normal to <20% in dogs, or <15% in cats (e.g. 10% or more)
- Absolute PCV 15-20% depending on history and presenting clinical signs
- If PCV < 10-12% immediate requirement
- Signs of specific organ hypoxia, even if don’t look very anaemic, particularly CNS
- Clear evidence of reduced oxygen carrying capacity e.g tachycardia/pnoea/bounding peripheral pulse
- Concern that PCV is likely to fall lower over period of time where transfusion would be difficult to organise
Describe whole blood
- “unaltered” blood from suitable donor
- Should be harvested aseptically into closed collection system
- Single unit = 450ml
- Must be transferred within 8 hours or must be refrigerated after collection
- All blood products are present and functioning
- Most common agent transfused in private practices
What is whole blood most appropriate for?
Animals that have been haemorrhaging e.g. in coagulopathies, thrombocytopaenia, whole blood loss due to trauma/surgical complications
What are packed red blood cells most appropriate for?
Anaemia due to haemolysis/chronic disease/erythropoietic failure)
Can use in conjunction with colloidal solution if animal needs whole blood but not available
What is fresh frozen plasma most appropriate for?
Coagulopathies
What is contained in oxygen carrying solutions?
No cells, no plasma proteins
Describe stored whole blood
- Fresh whole blood not transfused within 8 hours stored in fridge <4°C
- Storage life of 3-5 weeks depending on anticoagulant used
- Once transfusion begun must be complete in 4 hours
- lacks platelets, WBCs, labile clotting factors
In which conditions is stored whole blood most valuable?
Haemorrahge due to trauma, vit K dependent rodenticide toxicity, coagulopathies due to liver disease
How are packed red cell products produced?
- Prepared from whole blood by centrifugation
- Whole blood collected into system, plasma separated
- Red cells then resuspended in small volume of plasma and nutrient solution (e.g. SAG-M: sodium chloride, adenine, glucose, mannitol)
- PCV 70-80%
Describe the storage of packed red cell products
- Unit vol ~250ml
- Shelf life 3-6 weeks depending on preservative (SAG-M 6 weeks)
- Stored to enable air to circulate aroudn units
How are autologous transfusions carried out?
- Taken from animal, through in-line filter and back into itself
- Savenging systems available to harvest bnlood but not essential
- cavity blood drawn into sterile sysringe and driven back into patient using in-line filter or placed asempically into sterile empty fluid bags
What are the indications for use of autologous transfusion?
- Acute cavity haemorrhage due to trauma/coagulopathies
- Harvest blood ready later for transfusion when anticipating haemorrhage
What are the risks of autologous transfusions?
- Sepsis
- Dissemination of neoplasia (do not perform in ruptured haemagiosarcomas)
Outline the advantages of autologous transfusions
- reduced potential for exposure to allogenic blood
- Reduced risk of new infectious diseases
- Reduces chance of transfusion reactions,
- Immediate availability
- No need to anticoagulate if present in body cavity >1hour
How should autologous blood be transfused?
Using gravity feed rather - better survival of blood
What is fresh frozen plasma?
Plasma harvested from fresh whole blood within 8 hours of collection, and provides maximal concentrations of all factors
Describe the storage of fresh frozen plasma
If stored <20degreesC can be stored for up to 12 months
Give the indications and dose of fresh frozen plasma
- Acquired or inherited coagulopathies
- DIC, pancreatitis
- Liver disease
- Perioperative use for vWD or other inherited coaguloapthies
- Dose: 6-10mg/kg every 12 hours, up to 20 ml/kg for severe coagulopathy
Desribe stored plasma/frozne plasma (non-FFP)
- FFP >1 year old
- OR FFP that has been thawed or separaed from whole blood >8 hours after collection (up to 24 horus acceptable to prepare plasma)
- Some factor acitvity los but vit K dependent factors not labile so should be functional
- Can use up to 5 years from preparation if stored
What are the uses of stored plasma/frozen plasma?
- Anticoagulant rodenticide toxicity, haemophilia B
- Liver disease, DIC, pancreatitis
Describe oxyglobin
- No longer available
- cell free bovine polymerised ahemoglobin in LRS
- Stored as deocyhaemoglobin
- Binds oxygen less tightly than normal RBC-Hb, improved dissociation at lower tissue oxygen conc
- Once opened, discard within 24 hours
- Significant colloidal influence as well as oxygen carrying capacity
- Impact and duration of effect is dose dependent
What dose of oxyglobin will generate a PCV increase of:
a) 3% for 11-23hours
b) 12% for 74-82hours
a) 10ml/kg
b) 30ml/kg
What dose and rate of oxyglobin should not be exceeded in the dog?
- Dose not over 30ml/kg in 24 hour period
- Rate not exceeding 10ml/kg/hr
What dose and rate of oxyglobin should not be exceeded in the cat?
- Should not exceed 10ml/kg in 24 hour period
- Rate not exceeding 3ml/kg/hr
When is the use of oxyglobin indicated?
- Anaemia and circulatory collapse
- Care with volume replete patients
- Esp. good where rapid (temporary) oxygen provision is required
How does oxyglobin affect clinical pathology parameters?
- Due to heavy colour of product
- Biochem and optical coagulation methods
- Haematology less affected
- Machines directly measuring Hb will also measure oxyglobin
Briefly outline feline blood products
- No bank for feline blood/blood products in UK
- Problem of storage of feline blood is absence of true closed collection system
- Whole blood obtained from practice based donor schemes currently
- Human albumin used with some success in hypoalbuminaemic cats
What volume of blood raises the PCV of the recipient by 1% in dogs and cats?
- Dogs: donor PCV 45%, 2ml/kg raises by 1%
- cats: donor PCV 37%, 3ml/kg raises by 1%
Give the formulae for the volume to be transfused in cats and dogs
- Dogs: 1.5ml x desired PCV rise x BW in kg
- Cats: desired PCV rise (%) x BW in kg x2
What are the risks of giving blood as a colloid and as a shock/replacement fluid?
Calcium chelation and hypocalcaemia, influencing clotting cascade and platelet function/activation
Describe the standard rate of transfusion for dogs
- Usually 0.25ml/kg/hr for 1-20 mins followed by 0.5mg/kg/hr for 10-20 mins
- If no reaction, then increase rate to between 5-10ml/kg/hr to deliver blood within 4 hours
Describe the standard rate of transfusion for dogs and cats
Usually 1-3ml/hg for first 10-20mins then if all ok increase to 5-10ml/kg/hr if circulation status appropriate
What must not be co-adminsited with blood or blood products and why?
LRS - can lead to clotting or haemolysis
Describe the method of transfusion
- Often do not need to add supplemntary fluid when using packed red cells to reduce viscosity
- Chlorpheiramine prior to starting transfusion suggested, but evidence of stopping acute reaction is lacking
- Use cephalic, jugular or intraosseus
- Filtered giving set
- Infusion pumps give more reliable introduction of blood vs giving set
- Main factor in preventing haemolysis is storage
- Aim to complete within 4 hours to prevent contamination
- Do not warm blood
Compare the administration of blood transfusions to dogs and cats (and smaller dogs)
- Dogs: standard blood unit infused via blood giving set which contains filter to remove clots and other large fragments
- In cats/smaller dogs: syringe collection used, best administered by syringe driver and in-line pediatric filter
Outline the monitoring of blood transfusions
- TPR, resp effort, CRT, membrane colour every 5 mins for first half hour, during which rates change
- Then reduce checks to every 15-30 mins until completion
- Changes in parameters noted then reduce rate and review whether these continue to change
- PCV should be obtained after an hour or so, ensures some vol distribution has occurred making PCV more accurate
What is indicated if theimpact of a blood transfusion is lost within 24 hours?
Reaction or fulminable disease
How can the risk of non-immunological reactions to blood transfusions be minimised?
- Handle and store blood bags carefully
- Always use filtered giving set for administration
- Administer transfusions at an appropriate rate for the patient’s condition
- Monitor recipient closely during first 30 min of transfusion
- Consider initial slow flow rate (0.5mg/kg/kr during first 30 min of transfusion)
Describe the signs of a transfusion reaction in a type B cat receiving type A blood
- Massive intravascular haemolysis of type A donor blood
- May occur after admin of very small vols of mismatched blood
- Occurs rapidly
- May be fatal
Describe the signs of a transfusion reaction in a type A cat receiving type B blood
- Extravascular haemolysis leading to milder clinical signs
- Low half life of RBCs (2 days+)
- PCV will fall to pre-transfusion levels within days of the transfusion
- Can mimic ongoing haemolysis in cats with IMHA or haemorrhage
What are the consequences of of acute haemolytic reactions due to pre-formed antibodies (IgG usually) directed against RBC?
Acute intravascular haemolysis: DIC and death possible
Following a blood transfusion, what are the following signs indicative of?
Hyperthermia, tachycardia, dyspnoea, tremors, vomiting, collapse, haemoglobinuria
Acute intravascular haemolysis
Which animals are more at risk of acute intravascular haemolysis following blood transfusions?
Cats more than dogs, increased risk in dogs with increasing no. of transfusions
Compare the signs of acute intravascular haemolysis, and acute non-haemolytic blood transfusion reactions
Similar, but acute non-haemolytic usually without haemoglobinaemia/uria
What is the most common cause of an acute non-haemolytic transfusion reaction?
Bacterial contamination
What is the most common cause non-haemolytic transfusion reactions?
IgE and mast cell emdiated
Following a blood transfusion, what are the following signs indicative of?
Anaphylaxis i.e. urticaria, dyspnoea, vomiting
Non-haemolytic reaction
How do non-haemolutic, non-hypersensitive transfusion reactions occur?
Suspected due to broken down platelets or WBCs releasing inflammatory mediators. reduced by pre-sampling leukoreduction
Describe the signs of acute transfusion reactions (<24h)
- Pyrexia
- Depression
- Dyspnoea, tachypnoea, coughing
- Tachycardia or bradycardia
- Vomiting
- Vocalisation (cats)
- Urticaria (esp. dogs)
- Erythema or pruritus
- Tremors or seizures-
- Shock
- Cardiopulmonary arrest
Describe the clinical signs of delayed transfusion reactions (>24hours)
- Fever
- Anorexia
- Jaundice
- Often subclinical
- May get non-regenerative anaemia (e.g. myelodegenerative) in some dogs
What is a logical approach to non-haemolytic transfusion reactions
- Stop, provide antihistamine and possibly glucocorticoids
- May require circulatory support
What is a logical approach to any transfusion reaction?
- Stop immediately
- Clinical exam, esp: cardio, temp, haemoglobinaemia/uria
- Supportive treatment as indicated: fluids, corticosteroids, oxygen, antihistamines, adrenaline, diuretics
- Check blood typing or cross matching
- Check blood bag for evidence of lysis
List your differentials for a 3 day old foal that was initially normal and is now presenting with marked icterus, dark urine, loose yellow faeces, too weak to stand and unable to suckle
- Neonatal isoerythrolysis
- Portosystemic shunt
- Congenital liver dys/hypo/aplasia
- Sepssi
- Bacterial toxin
- EHV-1
- Clostridium leading to necrotising hepatitis
- Dehydration (dark urine)
- renal disease
- Hypoglycaemia (weakness)
What tests should be performed when presented with an icteric foal?
- Direct Coomb’s test
- Biochem and haematology
- Urinalysis
What emergency treatment should be provided to an icteric foal?
- Supplemental oxygen via nasal tube
- Urinary catheter
- Fluid therapy (vol depends on fluid deficit, 1L initially as a bolus)
What are the following haematology findings in a foal indicative of? RBC low, Hb low, PCV low Neutrophils high Monocytes high Low plasma proteins High icterus index = active jaundice Lactate high
Haemolytic anaemia, most likely neonatal isoerythrolysis
Outline the treatment for a foal with neonatal isoerythrolysis
- Fluids
- Blood transfusion (care re. blood transmitted diseases, wash with saline and centrifuge dam’s blood to remove alloantibodies)
- Give milk
- Antimicrobial therapy e.g. cefquinome
What IgG titres would indicate failed and successful antibody transfer following plasma transfusion in a foal?
- Failed: below 300-400mg/dL
- Successful: >8g/dL
