Coping with HYPOKALAEMIA

Low potassium blood levels can cause weakness and cardiac arrhythmias

- Dr Gill Jenkins

Mild hypokalaemia (low potassium in the blood), with potassium levels of 3.1-3.5 mmol/L, is probably the commonest electrolyte abnormality affecting hospitalised patients. In 5% of cases the potassium level is below 3.0 mmol/L, but even mild hypokalaemia can affect the heart rhythm. It’s commonly associated with the use of certain diuretics (water tablets) of the thiazide-type in the elderly, and also dietary disorders such as anorexia, causing gastrointestinal fluid loss through persistent vomiting, diarrhoea or laxative abuse. Other risk factors include accompanying illness such as heart failure, alcoholism and nephrotic syndrome.

Mild forms are generally asymptomatic, but in more severe conditions (potassium below 3.0 mmol/L), symptoms include tiredness, weakness, muscle pain and constipation. When severe (below 2.5 mmol/L), serious neuromuscular problems occur: severe weakness and paralysis, respiratory failure, bowel paralysis, tingling, numbness and muscle spasms.

Extensive investigations include bloods, urine checks and CT scans.

Management is almost always by potassium replacement. The amount and urgency depends on the severity, risk factors for arrhythmias (such as being elderly or having heart disease) and risk of ongoing losses (such as continuing diarrhoea). If below 2.5 mmol/L, admission is usually indicated, but if mild it may be treated more conservatively with oral replacement and regular monitoring. Underlying causes need treating, and medication such as thiazides may need to be replaced.