Emergency lab work Flashcards
What does PCV tell you? What other finding should you interpret with?
Measure of red blood cell mass:
- Volume percentage of red blood cells in the blood.
Examination of the tube after centrifugation allows examination of the plasma colour and clarity
* Icterus
* Haemolysis
* Lipaemia
A smear can be made from the buffy coat.
Needs to be interpreted with total solids (TS)
How are total solids measured?
Can be measured using a refractometer.
- Extract the fluid by scoring and snaping the microhaematocrit tube above the buffy coat layer.
Estimate for total protein based on the refractive index.
What can a decreased PCV and normal TS be a sign of?
- Haemolytic anaemia
- Anaplastic anaemia
- Anaemia of chronic disease
- Subacute or chronic haemorrhage
What can an increased PCV and normal TS be a sign of?
- Polycyathaemia vera
- Hyperthyroidism
- Hyperadrenocorticism
- Haemorrhagic gastroenteritis
- EPO-producing renal tumor
- Physiologic (e.g. sighthounds, dachshunds)
- Artefact d/t inadequate centrifugation
What can a normal PCV and a decreased TS be a sign of?
- Protein losing enteropathy
- Protein losing nephropathy
- Liver failure
- Third spacing
- Acute blood loss with splenic contraction
What can a normal PCV and an increased TS be a sign of?
- Multiple myeloma
- Feline infectious peritonitis
- Hyperglobulinaemia (e.g. chronic skin or dental disease)
- Dehydration and anaemia e.g. chronic renal failure
- Third spacing
What can increased PCV and TS be a sign of?
Haemoconcentration
What can decreased PCV and TS be a sign of?
- Chronic blood loss
- Subacute blood loss
- Overhydration (e.g. excessive intravenous fluid therapy)
- Splenic relaxation e.g. anaesthetic agents
What are normal PCV and TS values in cats and dogs?
Normal values :
* PCV 35-55% (dogs), 25-45% (cats)
* TS 55-75g/l (cats and dogs)
PCV and TS can be normal in acute blood loss
Where should you get blood for glucose readings? In what cases can you expect the reading to be low? When is it helpful to get a reading?
Ideally use a central vein (cf ear/ pad prick) because peripheral perfusion may be poor. PCV >65% is associated with false low readings.
Hypoglycaemia common in paediatric patients, animals with altered neurological status.
Can be compared with abdominal fluid in suspected septic abdomen (should be suspected if the systemic blood glucose concentration is >1.5mmol/l higher) and with affected limb/s in arterial thromboembolism whereby blood sampled from the jugular vein may have a glucose concentration >1.5mmol/l higher than that from the affected limb(s) .
How can you measure blood urea nitrogen (BUN)? What can it identify? What should be your next step if the result is abnormal?
- Can be measured using semi-quantitative enzymatic test strips.
- Screening tool used to identify possible azotaemia.
- If abnormal perform biochemistry.
When is lactate produced? What does an increased result indicate? How is it measured?
- Energy source produced by cells under anaerobic conditions. Increases in the plasma when the rate of production exceeds the rate of removal.
- Indicates degree of tissue hypoperfusion in types of shock, anaemia and sepsis.
- Useful prognostic indicator (e.g. in GDV) and can guide treatment and further diagnostic investigations.
- Measured using a lactate meter or blood gas analyser.
When is thoracocentesis indicated? What are its 2 purposes? What should you do with the fluid?
- Indicated if pleural effusion or pneumothorax is suspected or has been identified on POCUS.
- Most important for patient stabilisation but if pleural effusion is identified retain some fluid for diagnostics.
- Gross examination to determine whether chylous, haemorrhagic, purulent or transudate helps to guide immediate treatment.
- Further analysis for protein content, cytology, cell count, triglycerides and bacterial culture and sensitivity.
Where would you sample during abdominocentesis? What tubes would you put the fluid into? What results do you expect in cases of active bleeding, historic bleeding, urine, sepsis or bile?
Sample fluid from four quadrants of the abdomen.
EDTA tubes for cytology, heparinised tube for biochemistry
When is pericardiocentesis performed? What underlying cause could be associated if you find haemorrhagic fluid? What should be your next step?
- Perform to relieve cardiac tamponade.
- Retain some of the fluid for analysis:
- Biochemistry and cytology can be used to help identify the underlying cause.
- If haemorrhagic fluid is aspirate and you are unsure if either the heart has ruptured, or the atrium has been punctured perform a manual PCV before continuing to drain the effusion. Clotting is also suggestive of frank blood.
What useful information can urinalysis provide? What does isosthenuria and hypersthenuria suggest in a dehydrated and azotaemic patient?
- Urinalysis is quick and simple to perform and can provide useful information.
- Include urine specific gravity (USG) and Dipstick analysis
- Sediment smear analysis
- Isosthenuria in a dehydrated and azotaemic patient suggests renal dysfunction.
- Hypersthenuria in a dehydrated and azotemic patient suggests pre-renal aetiology.
What can blood gas analysers identify?
- Acid-base disorders
- Ventilation status
- Electrolyte imbalances
- Hyperlactataemia
- Serum glucose concentration
- Serum BUN, urea, creatinine
- [Haematocrit is often inaccurate, run a manual PCV/TS concurrently]
What can cause an increase in sodium? What clinical signs are associated?
-Inadequate water intake
-Excess free water loss
Thirst, confusion, weakness, lethargy, seizures, coma
What can cause a decrease in sodium? What clinical signs are associated?
- Relative excess water
- Impaired water excretion
- Hyperlipidaemia/ hyperproteinaemia (pseudohyponatraemia)
Nausea, vomiting, cerebral oedema (confusion, seizures, coma)
What can cause an increase in potassium? What clinical signs are associated?
-Impaired excretion d/t renal failure
-Impaired excretion d/t mineralocorticoid deficiency
-Impaired excretion d/t pseudo-hypoaldosteronism
-Drugs (e.g. ACE-inhibitors, potassium sparing diuretics, NSAIDs, cyclosporin)
Cardiac arrythmias, paraesthesia, weakness, paralysis, acidosis
What can cause a decrease in potassium? What clinical signs are associated?
-Increased excretion d/t diarrhoea
-Increased excretion d/t renal loss
-Mineralocorticoid excess
-Magnesium depletion
-Drugs (theophylline, B2 agonists, insulin, caffeine),
-Alkalosis,
-Hyperthyroidism
Arrhythmias, muscle paralysis, rhabdomyolysis, coma, metabolic alkalosis
What can cause an increase in calcium? What clinical signs are associated?
-Iatrogenic,
-Hyperparathyroidism
-Parenteral nutrition
-Hypervitaminosis D
-Neoplasia
Constipation, lethargy, stupor, coma
What can cause a decrease in calcium? What clinical signs are associated?
-Endocrine disease e.g. hypoparathyroidism, pseudohypoparathyroidism
-Vitamin D deficiency
-Renal disease
-Pancreatitis
-Sepsis
-Transfusion
Muscle cramps, hyperflexia, seizures
What can cause an increase in chloride? What clinical signs are associated?
-Loss of base through gastrointestinal tract
-Loss of base through renal excretion
Non-specific
What can cause a decrease in chloride? What clinical signs are associated?
-Severe vomiting
-Volume overload
-Drugs (loop diuretics)
Non-specific
What blood pH would indicate acidaemia and alkalaemia?
- Acidaemia: blood pH <7.35
- Alkalaemia: blood pH >7.45
How are the causes of respiratory acidosis/alkalosis and metabolic acidosis/alkalosis different?
Respiratory acidosis/ alkalosis: the primary disturbance is d/t abnormal partial pressure of carbon dioxide
Metabolic acidosis/ alkalosis: the primary disturbance is d/t an abnormality in an acid or alkali other than carbon dioxide
How can you distinguish compensated and uncompensated metabolic/respiratory acidosis or alkalosis?
Evaluate HCO3 and PCO2
What do negative and positive base excesses indicate?
Negative base excess (deficit) indicates metabolic acidosis.
Positive base excess (excess) indicates metabolic alkalosis.
What are normal anion gaps in cats and dogs? What does a high or low anion gap indicate?
A normal anion gap is 10-27 in cats and 8-25 in dogs
A high anion gap indicates the addition of an acid e.g. lactate, ketones, ethylene glycol (glycolic and oxalic acid) etc.
Note that albumin is the most abundant unmeasured anion so hypoalbuminaemia decreases the anion gap.
What values measure the oxygen bound to haemoglobin? What value measures oxygen dissolved in blood plasma? What proportion of oxygen is bound to haemobloding compared to that dissolved in blood?
98.5% of oxygen is bound to haemoglobin and this is measured by SaO2 and SpO2
The remaining 1.5% is dissolved in blood plasma and is measured as PaO2
What are potential causes of hypoxaemia?
- Reduced FiO2 (house fire) or reduced barometric pressure (climbed a mountain)
- Impaired diffusion
- V/Q mismatch (atelectesis or dead space)
- Right-to-left shunting (venous mixture)
- Hypoventilation
