Electroconvulsive therapy and serum potassium.

In 54 patients presenting for electroconvulsive therapy, the concentration of serum potassium was measured before and after the induced convulsion modified with a standard anaesthetic technique of methohexitone and suxamethonium. It was found that there was a statistically significant rise in serum potassium, but that the duration of convulsion had no significant effect on that rise in serum potassium. In a further 11 patients, methohexitone alone was administered without ECT, and it was found that serum potassium fell. Methohexitone, suxamethonium and ECT in combination cause a rise in serum potassium which is not clinically important unless pre-induction level is abnormally high, and prolonged convulsion does not exaggerate this rise.