Hypokalaemia
Background
Vomit contains relatively little potassium but severe vomiting causes hypochloraemic alkalosis due to loss of chloride and acid, which causes severe renal wasting of potasium and an intracellular shift of potassum.
Liquid stool has 10-50mmol l-1 - hypokalaemia early in diarhoea.
Renal loss K+ most often due to diuretics. Commonest is seen with large doses diuretics with secondary hyperaldosteronism as seen in heart failure, cirrhosis and nephrotic syndrome.
Other causes are primary hyperaldosteronism (Conn's) and Cushing's syndromes.
Causes
Intracellular shifts
- Alkalosis, Hi dose insulin, Periodic paralysis
GI loss
- D & V
- Ileostomy
- Purgative abuse
- Eating disorders
- Villous adenoma of rectum
Renal wasting
- Diuresis - drugs or osmotic ( Hyperglycaemia, Uraemia )
- RTA
- Hyperaldosteronism - Primary or secondary
Cushings - Bartter's synd
- Drugs - Liquorice, carbenoxolone, gentamicin XS
- Leukaemia
Key Clinical Features
Severe hypokalaemia < 2.5 mmol l-1
- dysrhythmias, dig toxicity and fasciculations
Moderate
- muscle weakness, absent reflexes, gut ileus
- reduced renal conc ability (Nephrogenic diabetes insipidus) with Na+ retention
Treatment and management
- Treatment PO replacement (bananas, orange juice)
- IV max potassium = 20mmol / hour with cardiac monitor and hourly U&E
