Serum potassium levels during prolonged hypothermia

Hypokalemia (mean serum potassium 2.3±0.4 mEq/l) was observed in six hypothermic patients (30°-32°C) with head injuries or brain hypoxia. In the first three patients, potassium was administered to maintain serum levels above 3.5 mEq/l and on rewarming after 48 h of hypothermia hyperkalemia (peak serum potassium=7.1±0.5 mEq/l) associated with cardiac arrhythmias developed. The remaining three patients received sufficient potassium to approximately replace measured losses during the hypothermic period. These patients did not become hyperkalemic on rewarming. Clinically insignificant sinus bradycardia, premature arrial contractions and junctional rhythms were seen during hypothermia with hypokalemia. We conclude that hypothermia produces hypokalemia by a shift of potassium from the extracellular to intracellular or extra vascular spaces. Potassium therapy during controlled hypothermia in the range 30°-32°C should only replace measured losses.