Compartmental shift of potassium--a result of sympathomimetic overdose

A 17-year-old youth was admitted with a serum potassium concentration of 1.8 mmol/l after taking an overdose of pseudoephedrine and choline theophyllinate. Apart from tachycardia, tachypnoea and ankle clonus, examination was normal as was the initial electrocardiograph. The hypokalaemia resolved, but there was an overall positive potassium balance of only 13 mmol. This suggests that the sympathomimetics provoked a compartmental shift of potassium perhaps indirectly by inducing hyperglycaemia and hyperinsulinaemia, as well as directly. Other factors known to affect body potassium distribution were excluded. The fact that features commonly associated with hypokalaemia could not be demonstrated may be explained by a normal body potassium content. Severe hypokalaemia caused by a compartmental shift occurs with large doses of sympathomimetics as well as in periodic paralysis.