Electrolytes & minerals

Question 1

Which electrolytes/minerals are extracellular?

Answer 1

Sodium
Chloride
Bicarbonate

Question 2

Which electrolytes/minerals are intracellular?

Answer 2

Potassium
Phosphate
Proteins
Magnesium
Sulphate

Question 3

Name the major cation in the ECF

Answer 3

Sodium

Question 4

What is the function of sodium?

Answer 4

Maintains water in the body

Question 5

How are sodium and water regulated in the body?

Answer 5

RAAS - controls circulating volume
ADH - controls osmolarity

Question 6

Describe the RAAS

Answer 6

• Renin converts angiotensinogen into angiotensin I
• Conversion of angiotensin 1 to angiotensin 2 is done by angiotensin converting enzyme (ACE)
• Angiotensin 2 acts on the adrenal gland to release aldosterone
• Angiotensin 2 also causes vasoconstriction -> increased BP
• Increased BP + aldosterone -> Na retention and water retention with K loss

Question 7

Describe the function of ADH

Answer 7

• ADH is released from the pituitary gland in response to an increase in blood osmotic pressure
• ADH causes increased permeability of the collecting duct
• Water is reabsorbed to prevent further dehydration

Question 8

Loss of sodium and water is due to?

Answer 8

Volume depletion

Question 9

What are the causes of hyponatraemia?

Answer 9

• Losing sodium: GI loss, kidney loss, Addisons, Drugs (Furosemide)
• Gaining water: CHF, iatrogenic
• Other: Increased plasma osmolarity e.g. severe hyperglycaemia

Question 10

What are the causes of hypernatremia?

Answer 10

1. Hypotonic fluid loss - lose water and abit of sodium: GI loss, kidney loss
2. Free water loss - losing water: heat stroke, pyrexia, diabetes insipidus, no access to water, adipsia
3. Gain salt - excessive intake

Question 11

Potassium concentration in plasma is controlled by?

Answer 11

Aldosterone

Question 12

Describe filtration of potassium

Answer 12

Freely filtered at the renal glomerulus then resorbed

Question 13

How are hypo and hyperkalaemia defined by plasma K concentrations?

Answer 13

Hypo = K < 3mmol/l
Hyper = K > 7.5mmol/l

Question 14

List the clinical signs of hypokalaemia

Answer 14

Muscle weakness
PU/PD
Anorexia
Ileus / constipation

Question 15

What are the causes of hypokalaemia

Answer 15

• Decreased intake: anorexia, fluid therapy with a low K fluid
• Translocation from ECF to ICF: insulin, catecholamines
• Loss: GI, renal, drugs

Question 16

What are the clinical signs of hyperkalaemia?

Answer 16

Muscle weakness
Cardiac abnormalities
- Bradycardia

Question 17

Describe the ECG of a pateint with hyperkalaemia

Answer 17

Lost P wave as the AV node cant work, spikey tall T waves
Atrial standstill
Life threatening conduction abnormalities
Fast rhythms are also possible

Question 18

What are the causes of hyperkalaemia?

Answer 18

• Artefactual
• Decreased urinary excretion: urethral obstruction, bladder rupture, addisons, drugs
• Translocation from ICF to ECF: insulin deficiency, tumour lysis syndrome
• Increased intake: iatrogenic, excess supplementation

Question 19

Name 2 drugs that could cause hyperkalaemia

Answer 19

ACE inhibitors
K sparing diuretics

Question 20

How is hyperkalaemia treated?

Answer 20

• IVFT: 0.9% NaCl, or Hartmann’s
• Insulin: can help drive potassium into cells
• Calcium gluconate
• Treat primary cause e.g. Addison’s, DKA, AKI, FLUTD, etc

Question 21

Name a hormone that affects potassium levels

Answer 21

Insulin

Question 22

Name a hormone that affects sodium levels

Answer 22

ADH

Question 23

What is the most important hormone for controlling plasma osmolarity?

Answer 23

ADH

Question 24

Failure of which organ is commonly associated with hyponatraemia?

Answer 24

Heart

Question 25

What % of calcium is ioinised?

Answer 25

50%

Question 26

What % of calcium is protein bound?

Answer 26

40%

Question 27

What is the main clinical sign of hypercalcaemia?

Answer 27

PUPD

Question 28

What are the most common causes of hypercalcaemia?

Answer 28

1. Malignancy - LYMPHOPROLIFERATIVE DISEASES = By far the most common cause - Anal sac adenocarcinoma - Many others 2. Renal failure 3. Primary hyperparathyroidism

Question 29

List some less common causes of hypocalcaemia

Answer 29

Addison’s disease Vitamin D toxicity E.g. Cholecalciferol rodenticide toxicity Bone lesions e.g. OSA Artefact: Lipaemia, haemolysis

Question 30

List the clinical signs of hypocalcaemia

Answer 30

Muscle tremors, twitches, cramps Seizures Restlessness, behavioural changes

Question 31

What needs to be ruled out as the cause of hypocalcaemia?

Answer 31

Hypoalbuminaemia Error: EDTA or citrate tube

Question 32

List the causes of hypocalcaemia

Answer 32

1. Eclampsia - From the day before whelping to about 2 days after - Emergence 2. Renal disease 3. Hypoparathyroidism 4. Post thyroidectomy in cats 5. Nutritional - all meat diet 6. Ethylene glycol toxicity 7. Acute pancreatitis

Question 33

Phosphate homeostasis is regulated by ...?

Answer 33

Parathyroid hormone (PTH)

Question 34

What is the overall effect of PTH?

Answer 34

Retain calcium and increase phosphorus excretion…i.e. to reduce plasma [PO4]

Question 35

List the causes of hyperphosphataemia

Answer 35

1. Failure to excrete - Decreased GFR e.g kidney disease - UT obstruction/rupture 2. Increased release from bone - Young animals 3. Increased intake - Hypervitaminosis D - High phosphate diet 4. Hypoparathyroidism 5. Tumour lysis syndrome 6. Spurious: Haemolysis: tends to be mild

Question 36

List the causes of hypophosphataemia

Answer 36

Rarely a clinical concern but can be sometimes: - Anorexia (cat) - Insulin use in DKA - Primary hyperparathyroidism - Hepatic lipidosis in cats

Question 37

In hypoparathyroidism, what happens to serum phosphate?

Answer 37

Increases

Question 38

You get some EDTA in your serum sample by mistake. What is the effect?

Answer 38

High K, low Ca

Question 39

A dog is overdosed on benazepril. What is the effect on serum electrolytes?

Answer 39

High potassium as RAAS is inhibited

Question 40

A dog presents with tremors, focal seizures, and pawing at the face. What electrolyte change is present?

Answer 40

Hypocalacemia