Suxamethonium pains and early electrolyte changes

Significant changes in the plasma electrolytes were found in a group of ninety-two female patients in the first 5 min following suxamethonium administration. The plasma potassium rose to a higher level in those patients who developed suxamethonium pains than in those who did not; the plasma calcium decreased in the former group, but increased in the latter. The plasma sodium decreased early in most patients, with the greatest reduction in those patients who did not develop symptoms. A decrease in the level of plasma calcium at 1 min correlated well with the incidence of 'the pains'. There were significant differences in the electrolyte changes, depending on whether thiopentone or Althesin was used for induction, but there was no difference in the incidence of suxamethonium pains. Suxamethonium pains are attributed to damaged muscle-spindles with enhanced calcium release playing an important part.