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.