Electrolyte imbalance

Question 1

what are the causes of hyponatraemia with a urinary Na < 20mmol/l?

Answer 1

extra-renal causes;
- diarrhoea, vomiting, sweating, burns

water excess;

• secondary hyperaldosteronism
• nephrotic syndrome
• IV dextrose
• psychogenic polydipsia

Question 2

what are the causes of hyponatraemia with a urinary Na > 20mmol/l?

Answer 2

renal causes;

• renal failure
• cerebral salt wasting syndrome
• salt wasting nephropathy
• diuretics
• addisons disease

euvolaemic patients;

• hypothyroidism
• SIADH

Question 3

what are the causes of hyponatraemia with a normal serum osmolarity?

Answer 3

pseudohyponatraemia

• hyperproteinaemia
• hyperlipidaemia

Question 4

what are the causes of hyponatraemia with a high serum osmolarity?

Answer 4

hyperglycaemia
alcohol
mannitol

Question 5

how would you treat a patient with severe hyponatraemia?

Answer 5

bolus hypertonic saline with or without conivaptan (vasopressin/ADH)

Question 6

at what Na level is hyponatraemia?

Answer 6

Na < 135 mmol/l

Question 7

at what Na level is hypernatraemia?

Answer 7

Na > 145 mmol/l

Question 8

what are causes of hypernatraemia?

Answer 8

HHS
dehydration 
Conn's syndrome
Cushing's syndrome 
Liddle's syndrome 
11 beta hydroxyls deficiency

Question 9

a patients test results show;
- serum Na > 135 
- urinary Na > 20 
- urinary osmolarity > 500 
the patient has a normal lying and standing BP 

what is the most likely cause of the hyponatraemia?

Answer 9

SIADH

Question 10

what are causes of SIADH?

Answer 10

malignancy 
respiratory 
- TB
- pneumonia 
neurological 
- SAH
- subdural haematoma 
- meningitis 
drugs
- carbamazepine 
- cyclophosphamide 
- NSAIDS 
- SSRI

Question 11

what are ECG features of hyperkalaemia?

Answer 11

tall tented T waves
small P waves
widening of QRS

Question 12

what are the ECG features of hypokalaemia?

Answer 12

U waves 
small/absent T waves 
prolonged PR interval 
ST depression 
long QT

Question 13

how is hyperkalaemia treated?

Answer 13

shift K from extravascular to intracellular

• insulin
• neb b2 agonists salbutamol

stabilise cardiac membrane;
- IV calcium gluconate

remove K from body;

• rectal calcium resonium
• loop diuretics
• dialysis

Question 14

how is hypocalcaemia treated?

Answer 14

mild/moderate - NaCl fluids

severe - IV calcium gluconate 10ml of 10% solution over 10 minutes

Question 15

how is hypercalcaemia treated?

Answer 15

rehydration with 0.9% NaCl

following hydration give bisphosphonates or calcitonin

Question 16

what are signs of hypocalcaemia?

Answer 16

chvostek sign
trousseau’s sign
prolonged QT interval on ECG

Question 17

what ECG changes are found in hypercalcaemia?

Answer 17

shortening of QT interval

Question 18

what is the normal range of calcium level?

Answer 18

2.1 - 2.6 mmol/l

Question 19

what are the causes of hypercalcaemia?

Answer 19

primary hyperparathyroidism 
malignancy 
- bones
- SCC lung cancer 
- myeloma 
addisons disease

Question 20

what are causes of hypocalcaemia?

Answer 20

CKD
vitamin D deficiency 
hypoparathyroidism 
acute pancreatitis 
pseudohypoparathyroidism 
contamination of sample with EDTA

Question 21

what are causes of hyperkalaemia?

Answer 21

addisons 
metabolic acidosis 
drugs: ACEI, ARB, spironolactone
AKI
rhabdomyolysis

Question 22

what are the causes of hypokalaemia?

Answer 22

with acidosis;

• vomiting
• thiazide like diuretics
• conns syndrome
• cushings syndrome

with alkalosis

• diarrhoea
• partially treated DKA
• renal tubular acidosis