Serum potassium changes during induction of anaesthesia.

Serum potassium levels of 53 patients before and after induction with halothane and oxygen, halothane, nitrous oxide and oxygen, and thiopentone, showed a significant decrease after reaching the first surgical plane. After the administration of the depolarizing agent suxamethonium serum potassium levels increased significantly more in the two halothane groups than in the thiopentone group. It is thought that both halothane and thiopentone reduce the number of depolarizations, whereas suxamethonium causes an acute increase in the number of depolarizations. Other factors that could influence serum potassium, such as decrease or increase in blood sugar, alkalosis or acidosis, were also investigated. It is concluded that they did not play a significant role in the measured potassium changes.