Serum potassium changes during hypothermia and rewarming: a case series and hypothesis on the mechanism

INTRODUCTION: Hypokalemia is known to occur in association with therapeutically induced hypothermia and is usually managed by the administration of potassium (K(+)). METHODS: We reviewed data from 74 patients who underwent a therapeutic hypothermia protocol at our medical institution. RESULTS: In four patients in whom data on serum K(+) and temperature were available, a strong positive correlation between serum K(+) and body temperature was found. Based on the close positive relationship between serum K(+) and total body temperature, we hypothesize that serum K(+) decreases during hypothermia owing to decreased activity of temperature-dependent K(+) exit channels that under normal conditions are sufficiently active to match cellular K(+) intake via sodium/K(+)/adenosine triphosphatase. Upon rewarming, reactivation of these channels results in a rapid increase in serum K(+) as a result of K(+) exit down its concentration gradient. CONCLUSION: Administration of K(+) during hypothermia should be done cautiously and avoided during rewarming to avoid potentially life-threatening hyperkalemia. K(+) exit via temperature-dependent K(+) channels provides a logical explanation for the rebound hyperkalemia. K(+) exit channels may play a bigger role than previously appreciated in the regulation of serum K(+) during normal and pathophysiological conditions.