Electrolytes imbalance

Question 1

Hypokalaemia

Answer 1

Potassium and hydrogen can be thought of as competitors. Hyperkalaemia tends to be associated with acidosis because as potassium levels rise fewer hydrogen ions can enter the cells

Hypokalaemia with alkalosis
vomiting
thiazide and loop diuretics
Cushing’s syndrome
Conn’s syndrome (primary hyperaldosteronism)

Hypokalaemia with acidosis
diarrhoea
renal tubular acidosis
acetazolamide
partially treated diabetic ketoacidosis

Magnesium deficiency may also cause hypokalaemia. In such cases, normalizing the potassium level may be difficult until the magnesium deficiency has been corrected

Question 2

Hypocalcaemia: causes and management

Answer 2

Causes
vitamin D deficiency (osteomalacia)
chronic kidney disease
hypoparathyroidism (e.g. post thyroid/parathyroid surgery)
pseudohypoparathyroidism (target cells insensitive to PTH)
rhabdomyolysis (initial stages)
magnesium deficiency (due to end organ PTH resistance)
massive blood transfusion
acute pancreatitis

Contamination of blood samples with EDTA may also give falsely low calcium levels.

Management
severe hypocalcaemia (e.g. carpopedal spasm, tetany, seizures or prolonged QT interval) requires IV calcium replacement
the preferred method is with intravenous calcium gluconate, 10ml of 10% solution over 10 minutes
intravenous calcium chloride is more likely to cause local irritation
ECG monitoring is recommended
further management depends on the underlying cause