MRCP revision battle 55.2: Hypokalaemia

Hypokalaemia is defined as K <3.5mmol; if <2.5mmol it is severe.


Symptoms/signs include:

• muscle weakness
• hypotonia
• cramps
• tetany
• worsening of dig toxicity
• cardiac arrhythmias

ECG may show:

• small/inverted T waves
• U waves
• long PR
• depressed ST

Causes of hypokalaemia


Low K with hypertension

• raised plasma renin
• Cushings
• renin-secreting tumour
• low plasma renin
• Conns
• liquorice
• Liddles

Low K without hypertension

• diuretics
• GI loss
• CRF
• Bartters
• Gitelmans
• secondary hyperaldosteronism

On to cryoglobulins...