Biphasic change in serum potassium concentration following a single dose of succinylcholine chloride.

Serum potassium concentration during the thiopentone-succinylcholine induction of endotracheal anesthesia was examined in 53 patients undergoing elective surgery. There was no change in serum potassium after thiopentone. During muscle fasciculation serum potassium fell by 0.37 meq/L and returned to the initial level by the end of fasciculation. During muscle relaxation there was a further rise of 0.41 meq/L. The expected increase in serum potassium following the administration of succinylcholine is shown to be preceded by a transient decrease.