U1 O3 - Emergency diagnostics Flashcards

Question

In what case would you see an increased Buccal mucosal bleeding time? What are the contraindications?

Answer 1

Instances where BMBT may be increased include: • thrombocytopaenia • von Willebrand’s disease • drug therapy e.g. aspirin. A BMBT should NOT be performed on dogs that are already known to be thrombocytopaenic- thrombocytopaenia should be confirmed initially on a blood smear, as previously discussed. Thrombocytopaenic animals will have a prolonged BMBT so confirmation with the test is unnecessary.

Answer 2

Secondary Haemostasis Secondary haemostasis is the process of clot formation using coagulation factors - it follows the formation of an initial platelet plug (Cornell University College of Veterinary Medicine, 2013). It can therefore be affected by deficiency in any clotting factor. These deficiencies may arise from a lack of production (e.g. vitamin K deficiency or haemophiliacs); or consumption of the coagulation factors (e.g. sepsis or trauma).

Answer 3

Activated partial thromboplastin time (aPTT) This assesses the function of both the intrinsic and common pathways. Activated partial thromboplastin time (aPTT) is measured from blood collected into a citrated plasma tube. The tube MUST be accurately filled as the results will be inaccurate otherwise.

Answer 4

``` Prothrombin time (PT) This identifies deficiencies in the extrinsic (factor VII) and common pathways (fibrinogen, II, V and X). It measures the time for fibrin to be produced after activation of factor VII, then factors X, V and II (prothrombin). Tissue factor and calcium are added to a citrated plasma tube, containing a blood sample, to activate. The tube MUST be accurately filled as an inaccurate result will be obtained otherwise. Fibrin formation, from fibrinogen, is the end point of the assay - this can also be measured using optical or mechanical means. ```

Answer 5

As with aPTT, deficiencies of less than 30% are required to produce prolongation of the PT. Factor VII has the shortest half-life of the clotting factors, so PT maybe increased before aPTT in a patient with a coagulopathy.

Answer 6

Acquired vitamin K deficiency (rodenticide poisoning) is an example of a condition that can prolong PT. Whilst eventually both PT and APTT will increase, PT will become elevated first-normally within 48-72hrs of ingestion of the rodenticide.

Answer 7

Activated clotting time. Activated clotting time is measured by taking a blood sample, then discarding the first 0.25-0.5 ml of it. This removes the tissue factor which could otherwise complicate the test. 2ml of the blood sample is put into a tube containing diatomaceous earth (produced by Becton-Dickinson, Oxford). After mixing, the tube is incubated at 37°C for 60 seconds in the dog; and 45 seconds in the cat. After thisthe 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. An in-house test-kit is also available for measuring activated clotting time (ACT). Sampling technique is important when considering coagulation profiles. Samples should be from a “clean stick”, with minimal dwell time in the vessel and they should be non-haemolysed. Other patient specific factors considerations need to be considered (e.g. a patient with a coagulopathy should not have jugular blood samples taken)

Answer 8

``` Slide Agglutination (also called saline dispersion test) A saline dispersion test should be performed to determine if there is true agglutination in a blood sample. N.B. Agglutination can arise with immune-mediated haemolytic anaemia when antibody covered RBCs stick together. In this test, a drop of blood from an EDTA blood tube or capillary tube is put onto a slide- it is assessed for the presence of agglutination (development of obvious flecks within the drop of blood). If agglutination appears to be present, three drops of saline are added to the blood on the slide. This will cause dispersal of RBCs if rouleaux (stacking of RBCS) rather than agglutination was present- the flecks will disappear with rouleaux. If true autoagglutination has occurred, the flecks will still be seen as the RBCs remain stuck together. Autoagglutination is caused by cross-linking of antibodies which are bound to the erythrocyte membranes - this is diagnostic for an immune-mediated component to the haemolysis. It is important to remember that the saline does not induce the agglutination – it merely confirms that it is true agglutination. ```

Answer 9

Coombs Test A Direct Antiglobulin Test looking for the auto-immune antibodies that are directed against the red cells (Coombs) can be used to confirm immune mediated haemolytic anaemia. Because the end (positive) result of this test is agglutination, the Coombs test need not be run if the patient is already auto-agglutinating. Blood should be taken for this assay prior to transfusion.

Answer 10

Point of Care Ultrasound

Answer 11

Focused assessment sonogram for trauma

Answer 12

Thoracic Focused Assessment with Sonography for Trauma

Answer 13

Abdominal Focused Assessment with Sonography for | Trauma

Answer 14

Colloid osmotic pressure

Answer 15

• the minimum database 1.3.3.1 Minimum Database A minimum database consists of the following: • Packed cell volume (PCV) • Refractometric total solids (TS) or total protein (TP) ** • Blood glucose (BG) • Blood urea (BUN) * blood smear * electrolytes * blood gases * urine specific gravity.

Answer 16

1.3.3.1 Minimum Database A minimum database consists of the following: • Packed cell volume (PCV) • Refractometric total solids (TS) or total protein (TP) ** • Blood glucose (BG) • Blood urea (BUN) • Blood smear

Answer 17

The volume of blood required for this database is small (~ 0.2ml depending on equipment used) and can be collected from the hub of an intravenous catheter at the time of placement (if the catheter was not flushed with heparinised saline prior to placement)

Answer 18

Separate venepuncture to collect blood for a MDB should not be necessary- merely adding to the patient morbidity. During catheter placement blood can also be collected for additional laboratory tests such as electrolytes/ venous blood gases (N.B. arterial blood gas analysis would require placement of an arterial catheter)

Answer 19

Total solids (TS) versus total protein (TP) - these terms are often used interchangeably but are not quite the same. Total solids (TS) refer to everything dissolved in plasma (plasma proteins, urea, triglycerides, cholesterol and glucose), while total protein literally refers to the main plasma proteins (primarily albumin and globulins).

Answer 20

``` Total solids (TS) refer to everything dissolved in plasma (plasma proteins, urea, triglycerides, cholesterol and glucose), ```

Answer 21

total protein literally refers to the main plasma proteins (primarily albumin and globulins).

Answer 22

The value for TP should therefore be slightly lower than TS. Most refractometers have been calibrated to give a TP measurement which is, in fact, the TS minus a small factor.

Answer 23

There are some breed and age specifics where PCV will be higher or lower (greyhounds/ sighthounds/paediatric patients)

Answer 24

Refractometric TS allows estimation of serum proteins and a rough estimation of colloid osmotic pressure (COP)

Answer 25

PCV is used to determine if a patient is anaemic or polycythaemic.

Answer 26

An increase in both PCV and TS is consistent with dehydration- although this may only be apparent with severe dehydration. A normal PCV/ TS could be present in a slightly dehydrated patient

Answer 27

An increase in PCV alone could be normal for the breed e.g. greyhound. It could be due to polycythaemia, but it could also be stress-induced (adrenaline/ epinephrine) splenic contraction

Answer 28

Decreased PCV and TS will often arise following haemorrhage or after aggressive fluid therapy

Answer 29

A decrease in both PCV and TS is not usually seen during/immediately following haemorrhage. During acute, active haemorrhage, whilst the total blood volume will be decreased, the PCV and TS may be normal because there has not yet been any fluid shift from the interstitial space to intravascular space (blood vessels). Soon there will be fluid movement from the interstitial space to the intravascular space causing dilution of the TS; the PCV is likely to be maintained near normal, initially, due to splenic contraction which releases more erythrocytes to improve oxygen delivering capacity. Therefore, if an animal is presented in shock with a low TS yet normal PCV, haemorrhage is the likely condition needing to be ruled-out. If the haemorrhage continues, both the PCV and TS are likely to decrease.

Answer 30

Low TS may also arise with a normal PCV if there has been protein loss/decreased production: (Hypoalbinaemia) primarily albumin (Mackin, 2010). This loss may be through the kidneys, GI tract or from the vasculature into a body cavity (thirdspacing) secondary to inflammation (e.g. peritonitis). Failure to produce can be associated with chronic liver disease or malnutrition.

Answer 31

Normal TS with a low PCV is consistent with enhanced erythrocyte destruction or a non-regenerative anaemia (Haemorrage, anaemia and hypoproteinamia)

Answer 32

Hyperglobinaemia | artifactual

Answer 33

(Chronic anaemia and haemolytic anaemia)

Answer 34

``` Pediatric patients Septic patients insulin secreting tumour Hypoadrenocorticism exercise induce (working dogs) ```

Answer 35

diabetes mellitus stress reponse (cats) In dogs, hyperglycaemia can be associated with head trauma and seizures- it is a poor prognostic indicator Patients with severe hypovolaemia or hypoxaemia may have hyperglycaemia due to the sympatho-adrenal response. However, depending on the individual patient it is possible they could be hypoglycaemic e.g., severe liver disease preventing gluconeogenesis

Answer 36

Azotaemia is when there are increased nitrogenous compounds in the blood stream e.g. urea and creatinine

Answer 37

Blood urea nitrogen (BUN) can be used as a screening test to identify azotaemic animals

Answer 38

A low BUN result on a dipstick is considered | accurate, but a high value should be supported with additional laboratory tests.

Answer 39

BUN may be elevated secondary to a pre-renal, renal or post-renal cause e.g., dehydration, renal disease or urethral obstruction

Answer 40

A blood smear provides vital information on the number and morphology of cells within blood. A blood smear should always be performed (and interpreted) if a haemotology profile is performed.

Answer 41

Erythrocytes, leukocytes and platelets should be evaluated - with attention paid to both the number and the cell morphology.

Answer 42

Cellular morphology should be viewed in the monolayer.

Answer 43

The presence of immature neutrophils (band cells) should be noted- this can indicate a severe inflammatory or infectious condition

Answer 44

In a patient with SIRS (septic or non-septic), leucocytosis may be present typically with a left shift (immature/ band neutrophils) and toxic changes to the neutrophils (eClinpath, 2013). Leucocytosis and mature neutrophilia can be part of a stress leukogram Septic patients may also be leucopaenic because of sequestration of white blood cells at the site of the infection (e.g. pyometra). Leucopaenia can also be present with viral infections e.g. parvovirus

Answer 45

Toxic changes that can be seen include- ➢ blue granules/ foamy appearance of the cytoplasm ➢ swelling of the nucleus ➢ Dohle bodies (light blue-grey, oval, inclusions in the peripheral cytoplasm)

Answer 46

Toxic neutrophils occur when the condition intensely stimulates neutrophil production, with decreased maturation time in the bone marrow.

Answer 47

The platelet count may be moderately decreased in bleeding or septic patients, secondary to consumption; or severely decreased and the actual cause of hypovolaemic (haemorrhagic) shock in a patient with blood loss.

Answer 48

Reducing levels of platelets in a critically ill patient can indicate that they are developing disseminated intra-vascular coagulation (DIC). Thrombocytopaenia is one of the earliest indicators of DIC.

Answer 49

• In healthy patients, under oil immersion (x100) microscopic examination, there should be 11-15 platelets per high power field (h.p.f.) in the monolayer. This is equivalent to a platelet count of ~ 165 - 225 x109platelets/l. Each platelet viewed, per h.p.f., equates to 15 x 109 / l in the bloodstream.

Answer 50

A patient with a platelet count of <5 per high power field should be closely monitored for evidence of bleeding

Answer 51

Less than 3 platelets per high power field (equivalent to equivalent to 0- 45x109 /L) is a dangerously low levels of platelets. Intervention would be indicated.

Answer 52

If the blood smear is stained with new methylene blue, then reticulocytes are demonstrated- they have a fine trabecular structure within the cells (made up of nuclear material and cellular organelles). In cats, reticulocytes may appear with punctuate dots/ clusters and lines of condensed organelles. These start out as the aggregate form (clusters and lines) and mature to the punctuate dots. Therefore, large numbers of the aggregate form of reticulocyte in cats demonstrates active regeneration

Answer 53

Nucleated red cell may be seen with a strongly regenerative response Nucleated RBCs may also be seen in cases of splenic disease, myelodysplastic conditions and lead intoxication

Answer 54

In dogs with immune-mediated haemolytic anaemia, there may be - Spherocytes- produced when macrophages remove part of the red cell wall. Strongly regenerative response Auto-agglutination

Answer 55

Fragments of red cells (schistocytes)

Answer 56

Fragments of red cells (schistocytes) may be secondary to haemangiosarcoma or disseminated intravascular coagulation

Answer 57

Heinz bodies are the result of oxidative damage to haemoglobin in red cells- they appear as refractile, poorly staining bodies, located beneath or protruding from the red cell membrane

Answer 58

In cats, the presence of Heinz bodies may suggest intoxication e.g. paracetamol or onion. Heinz bodies may also develop in cats with prolonged or repeated use of propofol. In addition, parasites e.g. Mycoplasma haemofelis or Babesia sp. may be present. Mycoplasma haemofelis may be seen as chains, discs or rods on the surface of erythrocytes. The PCV can decrease rapidly in cats with this condition.

Answer 59

Blood pH < 7.35

Answer 60

Blood pH > 7.45

Answer 61

Henderson- Hasselbach Equation - | CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3-

Answer 62

The main gases that are present in blood are oxygen (O2) and carbon dioxide (CO2).

Answer 63

The partial pressure of oxygen and carbon dioxide (PO2 and PCO2) represent the amount of the gas that is dissolved in blood.

Answer 64

Blood gas analysis can give essential information on the respiratory and metabolic status of a patient. It is important to note when considering respiratory status that arterial blood gases will be more accurate

Answer 65

Firstly, the acid/base status can be evaluated by assaying pH, PCO2 and bicarbonate

Answer 66

Secondly lung function can be assessed by measuring the amount of oxygen (PaO2) and carbon dioxide (PaCO2) in arterial blood. (N.B. a = arterial; v = venous)

Answer 67

Arterial blood gas analysis (ABG) is preferred when assessing respiratory status but venous blood gas analysis (VBG) will still yield useful information regarding metabolic status.

Answer 68

Determining the metabolic status of the patient will therefore provide vital clues to aid in the diagnosis of a condition, as well as help in the management/treatment of it. ➢ The presence of acidosis and alkalosis will also determine the type of fluid and replacement therapies indicated

Answer 69

Analysis of the respiratory component of the blood gas will help in the identification of a specific respiratory condition: as well as guiding therapy/intervention and prognosis. For example, deciding on when to provide supplemental oxygen. The use of arterial blood gases can help guide oxygen therapy protocols. Whilst oxygen is widely considered to be a benign therapy there is a risk of hyperoxia and associated complications. Monitoring of the PaO2 allows us to identify when we can reduce FiO2 for individual patients. N.B. Some figures are measured (e.g. pH) and some are calculated (e.g. BE). Animals with respiratory fatigue may need ventilation

Answer 70

The pH or acidity of the body is maintained within a relatively, narrow range (7.35– 7.45) through expiration of CO2 from the lungs; and the excretion of hydrogen ions through the kidneys. There are also a series of other buffers such as bicarbonate which act to keep the pH within narrow limits

Answer 71

Alterations to pH mean that cells and metabolic processes are unable to function leading to organ dysfunction, failure and ultimately death.

Answer 72

Any variation in the pH outside of this range will result in compensatory changes such as an increase/decrease in respiratory rate that will attempt to correct the pH: CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3- However, these compensatory changes, whilst maintaining pH, can result in increased energy and oxygen consumption for the patient.

Answer 73

Bicarbonate is very important | for the body’s ‘buffering’ system.

Answer 74

Plasma CO2 levels increase in animals that are hypoventilating- this is RESPIRATORY ACIDOSIS ↑CO2 + H2O → ↑H2CO3 → ↑H+ + ↑HCO3-

Answer 75

If a patient has METABOLIC ACIDOSIS e.g. diabetic ketoacidosis or lactic acidosis secondary to anaerobic metabolism, caused by hypovolaemia, it will often be tachypnoeic (rapid, shallow breathing). The tachypnoea is a compensatory response from the respiratory system to try and rid the body of acid (CO2) to maintain pH. This response results in more CO2 being expired and so more H+ ions binding with HCO3- to maintain equilibrium. With less H+ in circulation, this compensatory mechanism should assist the blood pH return to neutral. ↓CO2 + H2O → ↓H2CO3 → ↓H+ + ↓HCO3-

Answer 76

If a patient loses excess acid (hydrogen ions H+) through gastric vomiting or has excess bicarbonate, it will develop a METABOLIC ALKALOSIS - which results in the blood becoming more alkaline.

Answer 77

If a patient hyperventilates and expires too much carbon dioxide, it will develop a RESPIRATORY ALKALOSIS. This can also occur in anaesthetised patients undergoing IPPV or those receiving mechanical ventilation.

Answer 78

The kidneys assist in maintaining the correct pH but their response is not as immediate as that obtained by altered ventilation (Lungs)

Answer 79

The kidneys assist in maintaining the correct pH but their response is not as immediate as that obtained by altered ventilation. The kidney function is also commonly reduced in emergency patients, especially those that are hypotensive or hypovolaemic on presentation. As such supportive measures may need to be considered to optimise renal function.

Answer 80

``` When performing ABG the following are assessed: • pH • PCO2 • Bicarbonate (HCO3 - and ‘base-excess’) ```

Answer 81

If this an arterial blood sample (preferred) PaCO2, is | assessed; if this is a venous blood sample PvCO2, is assessed. carbon dioxide in blood

Answer 82

Increased CO2 (PCO2) levels in the blood stream decrease the pH of blood e.g. it becomes more acidic- acidaemia. As discussed previously, the cause is ineffective ventilation (hypoventilation). The animal therefore has a respiratory acidosis.

Answer 83

Decreased CO2 (PCO2) levels in the blood stream increase the pH of blood - alkalaemia e.g. it becomes more alkaline- the cause is hyperventilation. The animal therefore has a respiratory alkalosis.

Answer 84

metabolic alkalosis, bicarbonate will be increased.

Answer 85

In metabolic acidosis, bicarbonate will be decreased (less to mop up H+/ hydrogen ions);

Answer 86

Reasons for altered bicarbonate levels are - o Metabolic causes e.g. lost in diarrhoea, anorexia o Respiratory causes e.g. hypoventilation

Answer 87

Because bicarbonate levels can be affected by respiration, the concept of the base excess (BE) was developed to identify metabolic rather than respiratory causes of acid-base disorders (

Answer 88

The base excess (BE) is a calculated figure which estimates the metabolic (rather than respiratory) component of the acid-base balance Whilst we commonly evaluate pH, PCO2 and HCO3 to measure acidosis or alkalosis in the blood we can also evaluate BE to differentiate between the metabolic and respiratory components. It measures the amount of excessive base (alkali) or acid in blood and so gives information on the metabolic aspect of the acid-base balance.

Answer 89

It measures the amount of excessive base (alkali) or acid in blood and so gives information on the metabolic aspect of the acid-base balance. It calculates the amount of strong acid (or alkali - base deficit (BD)) that would theoretically have to be added to blood to neutralise it. The normal range is - 2→ +2 e.g. if a patient’s blood were alkaline for metabolic reasons, it would have too much base (e.g. increased HCO3). To neutralise the blood, strong acid would in theory be needed. The more alkaline the blood is the more acid would be required. The amount that is required is the base excess and it is an indication of how alkaline the blood is e.g. + 4 is less alkaline than +8.

Answer 90

If the number is more negative than it should be (e.g. -9) the patient has a base deficit. There is an excess of acid/ or lack of ‘base’/alkali in the bloodstream. This means more alkali/base would have to be added to neutralise blood. This shows that the patient’s blood too acidic= metabolic acidosis (more common)

Answer 91

If the number is more positive than it should be (e.g. +12) the patient has a base excess- there is an excess of ‘base’ (alkali)/ or lack of acid in the blood stream meaning more acid would have to be added to neutralise blood. This shows that the patient’s blood is too alkaline = metabolic alkalosis (less common)

Answer 92

As the body buffering system diagram demonstrates, blood CO2 levels (pCO2) can be altered quickly by altering ventilation (almost instantly). The kidneys are also involved in buffering, but this is a slower mechanism (2-3 days).

Answer 93

The anion gap calculation is used to determine whether metabolic acidosis is due to: o An increase in the level of acid in the system e.g. diabetic ketoacidosis, uraemic acids, toxins or lactate; o A loss of alkali (bicarbonate) e.g., from the kidneys.

Answer 94

Anions are negatively charged particles e.g. Cl- + HCO3 - present in extracellular fluid (ECF) (remember plasma is also part of the ECF);

Answer 95

cations are positively charged particles present in ECF e.g. Na+ + K+

Answer 96

Anion gap = (Na+ + K+) – (Cl- + HCO3-

Answer 97

The normal value for the anion gap for dogs is 8-25, i.e. normally dogs have 8-25 more positive ions than negative ions.

Answer 98

The normal value for the anion gap for cats 10-27 i.e. normally cats have 10-27 more positive ions than negative ions.

Answer 99

``` An increase in the anion gap (e.g. 40) in cases of acidosis, tells us that there are more anions (e.g. lactate, ketones. present than normal e.g. diabetic ketoacidosis. ```

Answer 100

However, a normal anion gap in a case of acidosis (identified from the BE calculation) tells us that the acidosis is due to a loss of bicarbonate (alkali) rather than increased acid e.g. diarrhoea

Answer 101

Blood lactate is considered a global indicator of tissue perfusion.

Answer 102

It can be used to assess tissue oxygenation; response to therapy and as a prognostic indicator.

Answer 103

Lactic acid is generated during anaerobic metabolism. This is most commonly secondary to decreased tissue perfusion, severe hypoxaemia; or a combination of these.

Answer 104

Lactic acidosis is the most common | cause of metabolic acidosis in veterinary medicine.

Answer 105

Normal serum lactate concentrations in dogs should be < 2.5 mmol/L (range 0.3 – 2.5 mmol/L). Concentrations greater than 2.5 mmol/L are considered clinically significant.

Answer 106

Lactate levels of 2.5 – 4 mmol/L are intermediate; lactate levels > 4 mmol/L are considered high.

Answer 107

Correlations have been made between lactate levels and likely patient mortality/prognosis (Young, 2012). Generally, the higher the lactate level, the poorer the prognosis. It is, however, more important to monitor trends in lactate levels - a significant decline in lactate would improve the prognosis whereas increasing lactate levels, in a patient, receiving treatment would give more cause for concern.

Answer 108

Prolonged vessel occlusion, excessive restraint, patient struggling, excessive panting, twitching and tremoring and delays in sample analysis will increase the serum lactate concentration, even in animals with adequate perfusion.

Answer 109

Lactate is most useful as a monitoring tool for gauging response to resuscitation in patients with shock.

Answer 110

Severe anaemia will result in a decreased oxygen delivery to tissues with the generation of lactic acid secondary to anaerobic metabolism. The presence of hyperlactataemia may therefore be utilised to aid in the decision to transfuse anaemic patients.

Answer 111

Lactate can also be used to analyse effusions from the abdominal cavity. In septic patients lactate levels will be increased in the effusion and glucose will be decreased due to anaerobic cellular metabolism taking place.

Answer 112

Sodium is the main extracellular cation (Na+) in the body. In addition to being involved in blood pressure control, muscle and nerve function, it is important in maintaining intracellular fluid (ICF) and extracellular fluid (ECF) water distribution and balance

Answer 113

The concentration of sodium reflects water balance; abnormalities in sodium are generally a result of gain or loss of water or sodium

Answer 114

Sodium can change osmotic gradients within the body leading to shifts of water into or out of cells e.g. cerebral oedema.

Answer 115

Hyponatraemia can occur in disease conditions such as intestinal obstruction (sodium is lost with the vomit), hypoadrenocorticism (sodium is lost from the kidneys) or a gain in free water (e.g. inappropriate use of hypotonic fluids).

Answer 116

(sodium is lost with the vomit

Answer 117

sodium is lost in the kidneys

Answer 118

Hypernatraemia can be seen in salt toxicity (gain in salt); a lack of free water (e.g. cat that has been accidentally locked in a shed for multiple days with no access to water) or because of iatrogenic administration of high sodium substances. Hypernatraemia can also be seen in disease processes e.g. hyperaldosteronism

Answer 119

causes cell dehydration

Answer 120

hyponatraemia results in cell oedema

Answer 121

Both conditions can affect neuron function potentially causing serious neurological signs. Whilst sodium is only one of the many electrolytes monitored, it is arguably one of the more important -plasma sodium concentration is the major determinant of plasma osmolality. Extremely high or low sodium levels must be carefully corrected to avoid neurological signs developing and avoid patient mortality.

Answer 122

Chloride (Cl -) is an extracellular anion which, along with sodium, is involved in water balance. Along with bicarbonate, it also has an important role in acid-base balance

Answer 123

hypochloraemia will occur secondary to a high gastrointestinal obstruction (because of loss of hydrochloric acid in vomit). Hypochloraemia is usually associated with metabolic alkalosis. Replacement of the chloride is essential to correct the metabolic derangement.

Answer 124

Hyperchloraemia may occur in a patient with diarrhoea- as the kidneys retain chloride ion when bicarbonate is lost, there may be metabolic acidosis. Iatrogenic hyperchloraemia may be caused by administration of saline fluids e.g. 0.9% NaCL (Rahilly, 2012). Chloride concentration may be artefactually increased in patients receiving potassium bromide as an anti-seizure medication

Answer 125

Potassium (K+) is the main intracellular cation. Because most potassium is located within cells, plasma / serum assessment does not necessarily accurately reflect the total amount of potassium in the body

Answer 126

Along with sodium, potassium plays an important role in nerve and muscle function

Answer 127

Plasma levels of potassium are dependent on diet, renal function, pH, insulin levels and cell integrity.Most of the body potassium is ingested

Answer 128

Insulin drives potassium into cells

Answer 129

Hypokalaemia, therefore, can be seen with anorexia, malnutrition, chronic vomiting or diarrhoea. It can also arise with renal disease due to increased diuresis, following insulin administration or secondary to drug therapy e.g.furosemide.

Answer 130

Potassium is excreted via the kidneys so decreased renal excretion can cause hyperkalaemia.

Answer 131

High levels of potassium lead to an atrial standstill which can lead to sudden and fatal arrhythmias

Answer 132

urethral obstruction, acute renal failure and typical hypoadrenocorticism can all result in hyperkalaemia.

Answer 133

Low levels of potassium can lead to | severe neurological dysfunction including intractable seizures

Answer 134

most of the body’s calcium is within mineralised bone -

Answer 135

~ 1% is in the ECF

Answer 136

The calcium ions (Ca 2+) in plasma can be: • free • bound to other substances e.g. albumin or phosphate (PO4 3− ).

Answer 137

Only ‘free’ calcium (in blood plasma) is biologically active

Answer 138

Only ‘free’ calcium is biologically active (involved in heart and muscle contraction)- this is often referred to as ‘ionised’ calcium.

Answer 139

The total level of calcium is affected by pH, vitamin D level, albumin level and diet.

Answer 140

There may be issues with the relative levels of calcium and phosphorus in unbalanced, home-made ‘all meat’ and ‘raw’ diets

Answer 141

Blood calcium levels can be affected by nutrition, endocrine disease, renal disease and neoplasia amongst other conditions

Answer 142

Hypercalcaemia can lead to cardiac dysrhythmias and acute renal failure - the most common cause is neoplasia . Hypercalcaemia can also be associated with renal failure, hyperparathyroidism, hypoadrenocorticism and vitamin D toxicity

Answer 143

Causes of hypocalcaemia include eclampsia, pancreatitis, ethylene glycol toxicity and diabetic ketoacidosis. Hypocalcaemia can result in muscle tremors, tachycardia, seizures and tetany.

Answer 144

Like calcium most phosphate (PO4 3−) in the body is found in mineralised bone

Answer 145

The unbound, free remainder is involved in several physiological processes e.g. maintenance of cell membrane, acid-base balance and cell energy production. Phosphate is a main intracellular ion

Answer 146

Phosphate levels are higher in young, growing animals than in mature animals.

Answer 147

Hyperphosphataemia is often seen in animals with renal failure due to decreased excretion

Answer 148

Hypophosphataemia, can develop with metabolic conditions such as diabetic ketoacidosis - this can cause haemolysis.

Answer 149

This is a main intracellular cation – magnesium (Mg 2+) has a similar distribution to calcium and phosphorus in the body. Most is found in muscle or bone.

Answer 150

As with plasma calcium, free/ ‘ionised’ magnesium is biologically active. (involved in heart and muscle contraction) Magnesium is involved in cell energy production and heart and muscle function

Answer 151

Hypomagnesia can be present in critical patients, especially if there are other electrolyte abnormalities. It is most seen in diabetic patients that are also hypokalemic. In the presence of refractory hypokalaemia, magnesium should be measured and supplemented as indicated. It can cause neuromuscular weakness, cardiac arrhythmias and anaemia.

Answer 152

Osmolality is a measure of the number of dissolved particles per unit of water e.g. how concentrated the fluid is.

Answer 153

Plasma osmolality is a measure of the number of dissolved particles per unit of water in plasma: ‘tonicity’. It indicates how concentrated the plasma is and is a good indicator of water-balance

Answer 154

As many critical patients have water imbalances, it is useful to be able to measure the osmolality of fluids e.g. plasma/serum. With water loss, there are relatively more dissolved particles per unit of water. The fluid is more concentrated e.g. hypertonic lots of particles in fluids

Answer 155

With water gain, there are less dissolved particles per unit of water. The fluid is hypotonic. A few particles in fluids - dilute

Answer 156

If the osmolality of two fluids is the same, this is called isotonic same number of particles in another fluid

Answer 157

Serum/plasma osmolality = 2(Na++K+) + BUN (blood urea nitrogen) + BG (Blood glucose)

Answer 158

Urine specific gravity (SG) measurement is often used as an indicator of urine osmolality.

Answer 159

Hyperbilirubinaemia is common in animals with sepsis (especially cats). In dogs it is thought to result from an endotoxin-induced defect in hepatocellular transportation of conjugated bile resulting in intrahepatic cholestasis; whereas in cats it is likely a result of haemolysis.

Answer 160

Clinical/blood biochemistry is the chemical analysis of blood (serum/plasma).

Answer 161

``` ALT ALKP BUN CREA BILE ACIDS TP ALBUMIN GLOBULIN ```

Answer 162

alanine aminotransferase

Answer 163

This is specific for liver cell damage - significantly increased levels are associated with hepato-cellular necrosis. The levels are frequently raised following trauma, hepato-toxicity and hypovolaemic shock.

Answer 164

alkaline phosphatase

Answer 165

Although this is found in several different tissues in the body, ALKP/AP is generally considered to provide information about bone and the liver- especially liver cell damage and biliary stasis.

Answer 166

Increased levels of ALKP/AP can be associated with hepatocellular disease, hepatobiliary pancreatitis, biliary obstruction, administration of steroids or high levels of endogenous steroid. It will be elevated in the juvenile patient due to increased osteoblast activity in bone

Answer 167

It will be elevated in the juvenile patient due to increased osteoblast activity in bone

Answer 168

An assessment of bile acid levels provides information about hepatic function

Answer 169

Bile acids are normally excreted into the gall bladder then into the gastrointestinal tract. 90% of bile acids are then reabsorbed from the intestine and transported back to the liver.

Answer 170

Alterations in bile acid levels may be seen in | association with a decrease in hepatic function such as portosystemic shunts.

Answer 171

An assessment of bile acid levels is usually made before and 1-2 hours after food (‘fasted’ and ‘post-prandial’)

Answer 172

Creatinine is formed at a regular rate by the breakdown of protein - it is then excreted by the kidneys

Answer 173

decreased renal excretion

Answer 174

Albumin | Albumin is the main plasma protein and is produced by the liver

Answer 175

Creatinine provides information about the functional capacity of the kidneys, in particular glomerular filtration rate.

Answer 176

Azotaemia is an increase in | nitrogenous blood products - creatinine and urea.

Answer 177

Elevated creatinine can be pre-renal (decreased kidney perfusion); renal (typically intrinsic/intrarenal causes) or postrenal (bladder rupture, urethral obstruction)

Answer 178

decreased kidney perfusion);

Answer 179

(typically intrinsic/intrarenal causes

Answer 180

bladder rupture, urethral obstruction)

Answer 181

Total protein | This is the sum of albumin and globulins

Answer 182

It is a large protein which has an important role in maintaining the intravascular colloid oncotic pressure i.e. it is very important in osmosis and intravascular fluid balance.

Answer 183

Total protein levels are mostly likely to be affected by altered levels of albumin

Answer 184

Decreased plasma albumin levels can be due to decreased production or increased loss

Answer 185

A decrease in albumin can be seen with gastrointestinal disease/protein-losing enteropathy (PLE), protein losing nephropathy, malnutrition, dilution (e.g. IVFT) and liver disease.

Answer 186

It can also occur secondary to serious inflammation with or without infection (e.g. pancreatitis/ sepsis) where vasculitis leads to leaking of albumin from the blood vessels (redistribution).

Answer 187

Globulin | There are three classes- alpha, beta and gamma.

Answer 188

Alpha and beta globulins are | produced in the liver and are involved in enzyme and cell transport functions

Answer 189

Gamma (immuno) globulins are produced by plasma cells and are involved in the immune response

Answer 190

There are different classes of immunoglobulins (Ig) e.g. IgG, IgA, IgM and IgD

Answer 191

Globulin levels are calculated by subtracting the albumin level from the total protein.

Answer 192

Increased levels are often seen with infection and | inflammation, due to increased production of gamma globulins

Answer 193

Liver disease: ammonia is converted to urea in the liver, so urea levels can be decreased with chronic liver disease (cirrhosis); or if the liver is bypassed e.g. portosystemic shunt.

Answer 194

Renal disease. Urea is excreted by the kidneys, so levels will be elevated by renal disease. As with creatinine, however, elevated urea levels could be prerenal (e.g. hypovolaemia/dehydration), renal or post-renal (urethral obstruction). Serum creatinine is a more reliable indicator of renal function.

Answer 195

Gastrointestinal haemorrhage (or very high protein diet)- the increased protein digestion will result in elevated urea levels, but creatinine will be normal.

Answer 196

The packed cell volume (PCV) is often also known as the haematocrit.

Answer 197

This is a measurement of the percentage of the blood volume represented by the red blood cells - it provides an indication of the oxygen carrying capacity of the blood.

Answer 198

The PCV and haematocrit are measured in different ways: • The PCV is measured manually using centrifuged blood and a microhaematocrit reader. • The haematocrit is calculated using an automatic analyser (

Answer 199

➢ Reticulocytes Reticulocytes are immature, non-nucleated red blood cells that are found in the circulation in increased numbers in regenerative responses.

Answer 200

➢ Reticulocytes Reticulocytes are immature, non-nucleated red blood cells that are found in the circulation in increased numbers in regenerative responses.

Answer 201

The mean cell volume provides information about the average size of red blood cells

Answer 202

Cells may be: • macrocytic (bigger than normal), • normocytic (normal size) • microcytic (smaller than normal).

Answer 203

Relates to cells size - bigger than normal

Answer 204

Relates to cell size normal size

Answer 205

relates to cell size - smaller than normal

Answer 206

RBCs become smaller as they develop in the bone marrow- so if immature are released early into the bloodstream e.g. following haemorrhage, they will be relatively large. In regenerative anaemia, immature cells are often released into the circulation and are relatively larger than mature erythrocytes

Answer 207

If a patient, has iron deficiency anaemia, the circulating red blood cells are smaller than normal as they have spent longer developing in the bone marrow, due to the lack of iron.

Answer 208

``` Mean cell (corpuscular) haemoglobin concentration (MCHC) This is a measurement of the average haemoglobin concentration per red blood cell ```

Answer 209

Depending on the haemoglobin levels in RBCs, they will be • normochromic (normal colour = normal haemoglobin concentration) • hypochromic (paler than normal = reduced haemoglobin).

Answer 210

normochromic (normal colour = normal haemoglobin concentration)

Answer 211

hypochromic (paler than normal = reduced haemoglobin).

Answer 212

Immature RBCs contain less haemoglobin- thus regenerative anaemia will usually be hypochromic; whereas non-regenerative anaemia will be normochromic.

Answer 213

Neutrophils: an increase in the number of neutrophils is most commonly associated with infection or inflammation.

Answer 214

The white blood cell count is made up of neutrophils, lymphocytes, eosinophil, monocytes basophils.

Answer 215

band cells

Answer 216

an increase in the number of immature neutrophils in the circulation is known as ‘a left shift’

Answer 217

This is seen where neutrophils are | involved in an active inflammatory or infectious process; or where there is abnormal neutrophil production.

Answer 218

In a normal regenerative response, the | number of mature neutrophils will outnumber the band neutrophils indicating that the immune response is working well

Answer 219

However, if band neutrophils outnumber the mature neutrophils, this indicates that the mature neutrophils are being consumed/destroyed- the immune response is not working as well as we would like or is being overwhelmed. This is called a degenerative left shift

Answer 220

Lymphopaenia (decreased circulating lymphocyte numbers)

Answer 221

Lymphocytes (T and B lymphocytes) are associated with the immune response

Answer 222

Lymphopaenia (decreased circulating lymphocyte numbers) can be seen in association with acute infection or chronic stress e.g. chronic disease or corticosteroid therapy etc.

Answer 223

Lymphocytosis (increased numbers of circulating lymphocytes)

Answer 224

Lymphocytosis (increased numbers of circulating lymphocytes) can be seen with hypoadrenocorticism, leukaemia or prolonged antigenic stimulation. It may also be seen with an acute stress response.

Answer 225

Eosinophils are present in relatively small numbers. They are associated with allergic disease and parasitism. Increased numbers may also be seen with specific conditions such as pulmonary infiltration with eosinophilia (PIE) or neoplasia. Eosinopaenia may be a stress response or secondary to corticosteroid treatment

Answer 226

FALSE - Basophils abnormalities in basophil numbers are rarely identified.

Answer 227

Monocytes these large cells are only present in blood for a short time before leaving and developing into macrophages.

Answer 228

Increased numbers can be associated with chronic, intracellular infections or a stress response

Answer 229

Haemostasis is the process of stopping bleeding by vasoconstriction and clot formation/ coagulation

Answer 230

vasoconstriction • primary haemostasis - formation of an initial platelet plug • secondary haemostasis/ clot formation - the platelet plug is stabilised by cross-linked fibrin- clot • thrombolysis- clot break-down.

Answer 231

Formation of an initial platelet plug

Answer 232

The platelet plug is stabilised by cross linked fibrin

Answer 233

Primary Haemostasis Platelets are required for primary haemostasis (the start of clot formation). Alterations in the platelet numbers occur for many reasons and with various diseases.

Answer 234

For example, thrombocytopaenia can arise due to: • Increased platelet destruction e.g. immune-mediated thrombocytopaenia (IMHA) • Increased platelet ‘consumption’: platelets have been used up secondary to haemorrhage or inflammation.

Answer 235

The monolayer segment lies between the feathered edge of the smear and the main body of the smear - it is composed of a single layer of cells.

Answer 236

Oil immersion fields are examined in the monolayer segment of the smear.

Answer 237

Therefore, a normal blood smear should have 11-15 platelets per field on average. Each one platelet, seen in an oil immersion (x100) field, is roughly equivalent to 15x109 platelets/l.

Answer 238

Dangerously low levels of platelets would be | indicated by less than 3 platelets per oil immersion field (equivalent to 0-45x109/l)

Answer 239

A true platelet count may be done, manually, using a haemocytometer, commercial diluting fluid and a microscope

Answer 240

A commercial ammonium oxalate diluent pipette system should be used (e.g. ‘Unopette Micro-collection System for WBC and Platelet Determination’ produced by Becton-Dickinson, Oxford UK). This is filled as directed and lyses the red cells after ~ 10 minutes. 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 then 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 241

Platelet function can be assessed in a laboratory using specific analysers. Clinically, however, the best way is to perform a buccal mucosal bleeding time

Answer 242

Buccal mucosal bleeding time - The BMBT requires the use of a commercial device that produces two standardised cuts to the buccal mucosa of the upper lip - 5mm long and 1mm deep. The patient is placed in lateral recumbency, the upper lip is reflected to expose the mucosal surface and held in place by a gauze tape lightly applied around the maxilla, enough to partially block venous return (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. The BMBT evaluates primary haemostasis by assessing platelet and vascular aspects of haemostasis

Answer 243

Instances where BMBT may be increased include: • thrombocytopaenia • von Willebrand’s disease • drug therapy e.g. aspirin.

Answer 244

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

Answer 245

It can be affected by deficiency in any clotting factor. These deficiencies may arise from a lack of production (e.g. vitamin K deficiency or haemophiliacs); or consumption of the coagulation factors (e.g. sepsis or trauma).

Answer 246

Secondary haemostasis is the process of clot formation using coagulation factors - it follows the formation of an initial platelet plug

Answer 247

Activated partial thromboplastin time (aPTT) This assesses the function of both the intrinsic and common pathways. Activated partial thromboplastin time (aPTT) is measured from blood collected into a citrated plasma tube. The tube MUST be accurately filled as the results will be inaccurate otherwise. Calcium and brain tissue thromboplastin (or a similar source of lipoprotein) are added to the citrated tube- this activates the clotting process leading to fibrin formation. The intrinsic and common pathway factors are activated in this process (factors XII, XI, IX, VIII, X, V, and II). Final fibrin formation can be monitored by optical or mechanical means. This is not a very sensitive test, as factors must be reduced to less than 30% of their normal values before the aPTT is prolonged. A dog with bleeding caused by haemophilia A (lack of factor VIII) or von Willebrand’s disease, may have a prolonged aPTT - it is, however, possible that aPTT could still be within the normal reference range.

Answer 248

``` Prothrombin time (PT) This identifies deficiencies in the extrinsic (factor VII) and common pathways (fibrinogen, II, V and X). It measures the time for fibrin to be produced after activation of factor VII, then factors X, V and II (prothrombin). Tissue factor and calcium are added to a citrated plasma tube, containing a blood sample, to activate. The tube MUST be accurately filled as an inaccurate result will be obtained otherwise. Fibrin formation, from fibrinogen, is the end point of the assay - this can also be measured using optical or mechanical means. As with aPTT, deficiencies of less than 30% are required to produce prolongation of the PT. Factor VII has the shortest half-life of the clotting factors, so PT maybe increased before aPTT in a patient with a coagulopathy. ```

Answer 249

Acquired vitamin K deficiency (rodenticide poisoning) is an example of a condition that can prolong PT. Whilst eventually both PT and APTT will increase, PT will become elevated first-normally within 48-72hrs of ingestion of the rodenticide.

Answer 250

Activated clotting time. Activated clotting time is measured by taking a blood sample, then discarding the first 0.25-0.5 ml of it. This removes the tissue factor which could otherwise complicate the test. 2ml of the blood sample is put into a tube containing diatomaceous earth (produced by Becton-Dickinson, Oxford). After mixing, the tube is incubated at 37°C for 60 seconds in the dog; and 45 seconds in the cat. After this 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. An in-house test-kit is also available for measuring activated clotting time (ACT). Sampling technique is important when considering coagulation profiles. Samples should be from a “clean stick”, with minimal dwell time in the vessel and they should be non-haemolysed. Other patient specific factors considerations need to be considered (e.g. a patient with a coagulopathy should not have jugular blood samples taken)

Answer 251

Additional laboratory tests Slide Agglutination (also called saline dispersion test) A saline dispersion test should be performed to determine if there is true agglutination in a blood sample. N.B. Agglutination can arise with immune-mediated haemolytic anaemia when antibody covered RBCs stick together. In this test, a drop of blood from an EDTA blood tube or capillary tube is put onto a slide- it is assessed for the presence of agglutination (development of obvious flecks within the drop of blood). If agglutination appears to be present, three drops of saline are added to the blood on the slide. This will cause dispersal of RBCs if rouleaux (stacking of RBCS) rather than agglutination was present- the flecks will disappear with rouleaux. If true autoagglutination has occurred, the flecks will still be seen as the RBCs remain stuck together. Autoagglutination is caused by cross-linking of antibodies which are bound to the erythrocyte membranes - this is diagnostic for an immune-mediated component to the haemolysis. It is important to remember that the saline does not induce the agglutination – it merely confirms that it is true agglutination.

Answer 252

If true autoagglutination has occurred, the flecks will still be seen as the RBCs remain stuck together. Autoagglutination is caused by cross-linking of antibodies which are bound to the erythrocyte membranes - this is diagnostic for an immune-mediated component to the haemolysis

Answer 253

Coombs Test A Direct Antiglobulin Test looking for the auto-immune antibodies that are directed against the red cells (Coombs) can be used to confirm immune mediated haemolytic anaemia. Because the end (positive) result of this test is agglutination, the Coombs test need not be run if the patient is already auto-agglutinating. Blood should be taken for this assay prior to transfusion.

Answer 254

Radiography uses ionising radiation, which is potentially harmful, but provides a wide viewing area e.g. the whole thorax may be seen. It provides clear images of bones and other organs. Ultrasound is non-invasive and provides ‘realtime’ (current) images that are constantly being updated. This can give information about the movement or function of some organs. It is very good at detecting ‘free fluid’.

Answer 255

Dorso-ventral The X-ray beam travels from dorsal to ventral (the patient is in sternal recumbency)

Answer 256

Ventro-dorsal The X-ray beam travels from ventral to dorsal (with the patient in dorsal recumbency) NEVER IF PATIENT DYSPNOEIC

Answer 257

Ventro-dorsal The X-ray beam travels from ventral to dorsal (with the patient in dorsal recumbency) NEVER IF PATIENT DYSPNOEIC Right lateral The animal is lying on its side with the right side closest to the cassette Left lateral The animal is lying on its side with the left side closest to the cassette N.B. lateral views are also not safe for a dyspnoeic patient

Answer 258

Rostrocaudal The X-ray beam passes through the skull in a rostral to caudal direction. The patient is positioned in dorsal recumbency. As this view requires general anaesthesia it is not likely to beperformed in the emergency presentation.

Answer 259

Oblique The X-ray beam passes through the area of interest at an oblique angle. This provides more information about the area under investigation by preventing superimposition.

Answer 260

Kilovoltage- penetrating power of the X-ray beam

Answer 261

milliampere seconds- number of X-rays

Answer 262

Focal (spot) Film Distance. This is also known as the | Film Focal Distance. It is the distance between the focal spot and the X-ray table

Answer 263

Radiodense/opaque material which is introduced into a | patient. Appears white on the radiograph

Answer 264

Radiolucent gas which is introduced into a patient. | Appears black on the radiograph

Answer 265

Both positive and negative contrast are introduced into the patient to provide maximum detail of the area being examined

Answer 266

Megahertz- measurement of the sound wave frequency

Answer 267

Ability of a structure to produce echoes

Answer 268

No echoes produced- appears black on ultrasound e.g fluid

Answer 269

Less echoes produced than adjacent tissues. Appears grey on ultrasound e.g. soft tissue

Answer 270

Very echogenic. More echoes produced than adjacent tissues. | Appears whiter on ultrasound e.g. relative more dense soft tissue, bladder calculus, bone

Answer 271

The same echogenicity as neighbouring tissue

Answer 272

Example- pleural effusion as the cause of respiratory distress in a dyspnoeic patient is likely to be apparent from the clinical examination. Therefore, rather than performing radiography at this stage, which will only confirm what was already apparent, and could cause the patient’s condition to worsen, the veterinary surgeon is likely to perform emergency thoracocentesis (removal of the pleural effusion), following a period of oxygenation. Not only will this be diagnostic, but it will help to improve the patient’s condition. Following this, with the fluid removed and the patient’s condition improved, radiography might be appropriate- it should be safer and the underlying cause of the effusion may be apparent e.g. liver lobe incarcerated in the thorax secondary to diaphragmatic rupture.

Answer 273

A dorsoventral view is the only projection that should be considered if the animal has breathing difficulties.

Answer 274

Although dorsoventral thorax is the usual orthogonal view especially for imaging the heart and the caudal lung lobes, occasionally a ventrodorsal radiograph of the thorax should be obtained as well. The ventrodorsal view is preferred where the main area of interest includes the cranial mediastinum, caudal vena cava or accessory lung lobe.

Answer 275

On the lateral radiograph the width of the heart is normally 2.5-3.5 intercostal spaces in dogs; and 2 intercostal spaces in cats. T

Answer 276

The height of the heart is roughly two thirds | of the height of the thoracic cavity in both dogs and cats, although there are breed variations

Answer 277

On the dorsoventral view the heart is roughly two thirds of the width of the thoracic cavity

Answer 278

On a lateral view of the thorax, the apex of the heart should sit just above the sternum. If elevated it might indicate the presence of air or fluid

Answer 279

The vertebral heart score technique can be used to assess cardiac size. There is some variation of vertebral heart score between different breeds. On a lateral view of the thorax the long axis of the heart (from carina to the apex of the heart) and the short axis (widest part of the heart in a line at right angles to the long axis) are measured. These lengths are then compared to the number of vertebrae from the cranial edge of T4. This will then give a length for each axis in whole/part thoracic vertebrae. Adding these two scores together gives the vertebral heart score (IMV, 2011). Suggested normal values for dogs are 8.5–10.7; the normal value for a cat should be < 8.

Answer 280

Enlargement of the heart will present as a change in the cardiac silhouette and alterations in the position of neighbouring structures e.g. elevation of the trachea. Alterations in the lung patterns such as air bronchograms or increased lung density may also be present if the patient has pulmonary oedema.

Answer 281

Cardiomegaly can be associated with a variety of conditions including vascular disease, congenital cardiac disease (e.g. patent ductus arteriosus) and cardiomyopathies.

Answer 282

In left-sided congestive heart failure the pulmonary veins will be enlarged compared to the arteries, and there may be peri-hilar alveolar/interstitial pattern in the dog; or diffuse/patchy interstitial/alveolar pattern in the cat.

Answer 283

Enlargement of the cardiac shadow could also be due to pericardial disease rather than enlargement of the heart itself as soft tissue and fluid have the same radiographic opacity. Pericardial effusion is quite common in the emergency patient – it can be idiopathic, haemorrhagic (e.g. coagulopathy), neoplastic or infectious. The cardiac shadow is usually very rounded and enlarged on a thoracic radiograph of a patient with a pericardial effusion- however ultrasound is more sensitive for diagnosing this condition as it can differentiate between fluid and soft tissue unlike radiography

Answer 284

vascular pattern bronchial pattern alveolar pattern interstitial pattern

Answer 285

• Vascular pattern | o Increased or decreased width of pulmonary vessels due to congestion or hypovolaemia.

Answer 286

Bronchial pattern o Thickening of the bronchi associated with inflammation (e.g. feline ‘asthma’)

Answer 287

Alveolar pattern o The presence of fluid in the alveoli results in a fluffy appearance of the lung fields. This could be caused by oedema (heart failure, drowning), haemorrhage or pneumonia (e.g. aspiration). There may be air bronchograms

Answer 288

• Interstitial pattern- increased opacity of the interstitial tissue which can be nodular or unstructured o e.g. oedema, pneumonia, haemorrhage, neoplasia, abscess.

Answer 289

Assessment of the bony structures of the thorax should be made • Fractured ribs / sternum o May be associated with pulmonary contusion o There may be a flail chest o There may be fractured ribs close to the vertebrae in a cat with feline asthma syndrome

Answer 290

If radiography is performed, changes indicative of pneumothorax include retraction of the lung from the chest wall (loss of vascular markings in this space), consolidation of lung lobes; and, on the lateral radiograph, the appearance of the heart “floating” on a cushion of air. The latter radiographic finding is due to the heart ‘falling’ to the side of the atelectatic (collapsed or airless) “down” lung. N.B. If a patient is dyspnoeic, as is likely with significant pleural space disease, a lateral view should NOT be attempted.

Answer 291

Retraction of lung lobes will be present. Interlobar fissures may also be more prominent due to the surrounding fluid; and it will probably be difficult to see the cardiac shadow.

Answer 292

The final image will depend on the amount and type of tissue that has passed from the abdomen into the thorax. The presence of a pleural effusion may obscure other findings. Part or all the lung fields may be obscured; intestinal gas shadows may be present in the thorax. Diaphragmatic rupture can cause unilateral or bilateral radiographic changes - the normal diaphragmatic outline will not be visible.

Answer 293

On the lateral view, air within the mediastinum will increase contrast in this area; resulting in structures, such as the aorta, which are not normally visible in this area being seen.

Answer 294

Fluid within the mediastinal space will make the mediastinum more obvious on dorsoventral view- it will appear wider

Answer 295

These may be obvious as soft tissue density or may | displace the surrounding tissues such as the heart and trachea.

Answer 296

``` o Pericardio-peritoneal diaphragmatic hernia o Megaoesophagus may be visualised o Tracheal collapse mediastinal mass mediastinal fluid pneumomediastinum pneumothorax pleural effusion diaphragmatic rupture` ```

Answer 297

``` • Acute abdomen o Vomiting o Abdominal pain • Following a road traffic accident • Vomiting • Suspected gastro-intestinal foreign body • Gastric dilatation +/- volvulus • Bladder rupture • Blocked urethra • Pyometra • Ascites (although radiographically there will be poor abdominal contrast if there is free fluid) • Confirmation of whether Caesarean is required ```

Answer 298

use a grid for larger animals (> 10-15 cm tissue | depth).

Answer 299

In the emergency patient, ultrasound can be used for identification of free fluid or to obtain more information on specific organ(s) e.g. an enlarged uterine outline, as indicated by radiography, can be shown to be distended and fluid filled in a patient with pyometra (VetGirl, 2018) if ultrasound is performed. The urinary bladder, gall bladder, uterus, prostate, spleen and pancreas can all be assessed relatively easily during emergency ultrasound. In addition, foetal heart beats can be visualised. This allows for monitoring of the pregnant patient and foetuses. Ultrasonic evidence of foetal distress (e.g. heart rate < 160-190/ bpm) could be an indication for proceeding to Caesarean section

Answer 300

The aim of the ultrasound examination is prompt detection of free fluid

Answer 301

Four areas are examined in two planes Subxiphoid or diaphragmatico-hepatic (DH) site ▪ Left paralumbar or spleno-renal (SR) site ▪ Off midline over the bladder or cysto-colic (CC) site ▪ Right paralumbar or hepato-renal (HR) site

Answer 302

Abdominocentesis can be performed using either an open or closed technique.

Answer 303

The closed technique involves attachment of a syringe to the needle prior to insertion, with fluid being collected by aspiration of the syringe. This prevents air from entering the abdomen: this would be apparent as a pneumoperitoneum on radiographs. The disadvantage of this technique is the potential occlusion of the needle bevel by omentum

Answer 304

An open technique relies on passive gravitational flow of fluid from the abdomen rather than syringe aspiration. A needle or catheter is inserted in the most gravity-dependent portion of the abdomen and fluid allowed to flow by gravity. With an open technique, there is a risk of air entering the abdomen causing a pneumoperitoneum. This may be visualized radiographically and complicate their interpretation.

Answer 305

Using an aseptic technique, a 21 gauge (g) 1 to 1.5-inch hypodermic needle (dog) or 23 g ¾ inch needle (cat) is introduced into the abdomen, possibly under ultrasound guidance. To avoid splenic injury, abdominocentesis is usually performed with the patient in sternal or left lateral recumbency – although if free fluid has been identified following ultrasound examination, the position of the patient for abdominocentesis will be dictated by where the fluid is located. ▪ Fluid may be collected into plain and EDTA tubes for analysis (PCV, TS, cytology, chemical analysis +/- culture and sensitivity); a slide should ideally be prepared for in house microscopic examination.

Answer 306

``` The size, shape and opacity of the abdominal structures should be assessed. a slide should ideally be prepared for in house microscopic examination. The position of the following should also be noted: • Stomach • Duodenum • Small intestine • Large intestine • Liver • Pancreas • Spleen • Bladder • Female/male reproductive tract • Kidneys (retro-peritoneal) ```

Answer 307

If a patient is suspected of having e.g. an intestinal foreign body, if its condition is stable, it is acceptable to wait a few hours (~4-6hrs) to re-Xray, for consistent signs of an obstruction, rather than e.g. every hour. It is imperative that diagnostic radiographs are produced even in an emergency.

Answer 308

``` Due to the large number of abdominal organs, numerous radiographic abnormalities could be identified. Emergency conditions that could demonstrate radiographic abnormalities (contrast may be required in some cases) include: • GDV • Abdominal/ peritoneal effusion • Foreign bodies • Intussusception • Free gas (pneumoperitoneum) • Hepatomegaly • Distended/ ruptured bladder • Renoliths/ ureteroliths/ uroliths/ uretholiths • Dystocia/pyometra • Hernia/ body wall rupture • Splenic tumour • Prostatomegaly ```

Answer 309

Radiography can differentiate gastric dilation from GDV. A right lateral (and possibly a dorsoventral view) should be obtained. N.B. a ventrodorsal view would be contraindicated in this situation due to the patient having impaired ventilation and blood flow.

Answer 310

The stomach appears as a large, distended, gas-filled structure- the pylorus is in an abnormal position if volvulus has occurred. It is located dorsally and slightly cranial to the fundus. There is usually compartmentalisation/ reverse "C” sign - a band of soft-tissue between the pylorus and fundus due to the ‘twist’.

Answer 311

Decreased abdominal detail/ contrast (ground-glass appearance) can be caused by - • abdominal effusion • absence of abdominal fat (e.g. in a puppy or emaciated animal) • pancreatitis (localised).

Answer 312

Although an intussusception can affect any part of the intestine, the most affected area is the ileocaecocolic junction

Answer 313

This can be confirmed with ultrasound or a barium sulphate study (enema). As barium fills the space between the two layers of the intussusception, it takes on the appearance of a coiled spring. N.B. As with all contrast studies, barium sulphate should not be administered if there is suspicion of gastro-intestinal rupture/ perforation due to the risks associated with barium leaking into the abdomen

Answer 314

Barium sulphate is a positive contrast agent that is used exclusively in the alimentary tract

Answer 315

Barium sulphate suspension (liquid) or barium impregnated polyethylene spheres (BIPS) can be used to examine the gastrointestinal tract, for identification of intestinal obstructions, strictures etc. A barium meal (barium sulphate mixed with food) can be used to confirm megaoesophagus

Answer 316

Barium sulphate should NOT be given if there is any concern about an alimentary tract rupture e.g. oesophageal perforation. If administered orally, great care must be taken to avoid aspiration especially in a patient suspected of having megaoesophagus

Answer 317

Intravenous urography can be used to examine the structure, and function, of the urinary tract (especially the upper urinary tract - kidneys and ureters).

Answer 318

The patient must be well-hydrated and non-azotaemic before performing this procedure so pre-procedure stabilisation will be indicated.

Answer 319

To be diagnostic, the bladder requires to be fully inflated BUT if too much contrast is introduced, there is a risk of bladder rupture especially in patients with chronic ongoing inflammation.

Answer 320

The procedure must be performed aseptically. The patient should have a urinary catheter placed and urine is first drained from the bladder, using a three-way tap and syringe. Contrast is then gradually introduced into the bladder. During the procedure, the bladder should be carefully palpated to assess its size. If it feels ‘full’ via the abdomen or if there is resistance to introduction of contrast, no more should be introduced, and a check radiograph of the caudal abdomen should be obtained. If the bladder is not fully inflated, more contrast can be introduced. The AVERAGE amount of contrast that can be introduced into the bladder is 5-10ml/ kg but there is much individual variation depending on the underlying condition. If a bladder is chronically inflamed e.g. feline lower urinary tract disease, 1-2 ml/kg may be the maximum amount that could be safely introduced. At the end of the contrast study the contrast should always be drained from the bladder.

Answer 321

Pneumocystography is used to examine the bladder. Room air is generally used - although pure gases e.g. carbon dioxide and nitrous oxide from a cylinder will produce better contrast and are also safer, as more soluble in blood (Zlot and Webster, 2011). The contrast produced with this technique is less good than with double contrast cystography.

Answer 322

There is a risk of air embolism when gas is introduced into the bladder - it is advised that the patient should be positioned in left lateral recumbency to avoid this. Because carbon dioxide (CO2) and nitrous oxide (N2O) are highly soluble there is less risk of air embolism if they are used rather than room air or oxygen. N.B. If it is likely that the patient’s mucosa is very inflamed, air should be avoided due to the increased risk of air embolism. It is also essential to avoid overdistension of the bladder.

Answer 323

Double contrast cystography is used to provide optimum detail of the bladder mucosa and the lumen e.g. masses or radiolucent calculi can be seen.

Answer 324

A small volume of iodinated, water soluble contrast material is introduced into the bladder. The patient is rolled carefully to encourage the contrast to coat the mucosa. The bladder is then fully inflated with air, CO2 or N2O as for pneumocystography. A double contrast cystogram may also be obtained after positive contrast cystography. Most of the positive contrast is removed from the bladder and replaced with air

Answer 325

Positive contrast cystography can be used to identify bladder rupture and large filling defects e.g. tumour. The technique is the same as for pneumocystography but using iodinated positive contrast media instead. The large volume of contrast could obscure some small filling defects. Ionic, hyperosmolar products can be used for bladder studies e.g. Urografin® (meglumine amidotrizoate / sodium amidotrizoate) but non-ionic, hypoosmolar products may be as cost-effective and less irritant.

Answer 326

A contrast study maybe performed to provide more information about the spinal cord e.g. is there spinal cord compression that will require surgery and if so where is it? Due to the risks associated with movement, the patient must be anaesthetised for this procedure. The contrast medium used must be non-ionic and hypoosmolar (or third generation if available). For cervical/cisternal myelography, a calculated volume of warmed contrast is injected into the subarachnoid space via the atlanto-occipital space. This is generally better for imaging the cervical/thoracic spine

Answer 327

The area must be surgically prepared as sterility is of the utmost importance and we must avoid introduction of bacteria into the cerebrospinal fluid (CSF). With the patient in lateral or ventral recumbency the skin from the occipital process of the skull, out to the wings of the atlas and caudally to the third cervical vertebra is clipped and surgically prepped. If the patient is in lateral recumbency care needs to be taken to ensure that the endotracheal tube does not kink when the head is flexed to allow injection of the contrast. Cerebrospinal fluid can be collected for analysis, prior to injection of contrast media. Removing an equivalent volume of CSF to the amount of contrast to be introduced means there is less risk of increasing the pressure in the subarachnoid space- this is important as increased pressure could cause seizures. Following administration of contrast, the patient must be positioned with its head elevated to prevent contrast entering the ventricles. This can be achieved with sandbags or elevated platforms in beds. As a chemical agent has been introduced into the subarachnoid space and is mixed with CSF, it is important to be aware of the potential for side-effects

Answer 328

The patient should be monitored constantly until fully recovered from the anaesthetic; and following myelography the patient animal should be supported in sternal/ventral recumbency, with its the head elevated, to prevent contrast entering the ventricles of the brain. The patient must be closely monitored for seizures during recovery form myelography, especially if cisternal myelography is performed.

Answer 329

Fructosamine

Answer 330

Ventrodorsal and lateral

Answer 331

An obese 12 year old Labrador Retriever

Answer 332

Intussusception

Answer 333

It can confirm tempero- mandibular luxation

Answer 334

The correct answer is: Non-ionic, hypoosmolar iodine based

Answer 335

The correct answer is: immature red blood cells

Answer 336

The correct answer is: Buccal mucosal bleeding time

Answer 337

The correct answer is: Bladder

Answer 338

The correct answer is: Arterial blood gas analysis

Answer 339

SpO2 should be > 94-95%. This equates to PaO2 > 80 mmHg

Answer 340

Serum lactate levels are likely to be increased due to cell anaerobic respiration

Answer 341

The correct answer is: decreased HCO3-

Answer 342

The correct answer is: Gastric dilation & volvulus