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

Abstract

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 therapeutic hypothermia protocol at our medical institution. Results In 4 patients in whom close data on serum K+ and temperature was available, a strong positive correlation between serum K+ and body temperature was found during the rewarming phase when serum K+ increased. Based on the close positive relationship between serum K+ and total body temperature, we hypothesize that serum K+ falls 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 Na+/K+/ATPase. 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.

The hypokalaemia that came from the cold

“…To some extent, the same applies to hypokalaemia associated with hypothermia. Boubes and colleagues [ 1 ] have added to the intrigue with their current paper and present food for thought for nephrologists who are interested in unusual electrolyte disorders. Acute physicians, intensivists and nephrologists should be more aware of this unusual association when they see patients with hypothermia of whatever cause.…”

“…For example, metabolic acidosis can occur with hypokalaemia, as reported in subjects after immersion in cold water [ 27 ]. It is possible that as yet unidentified ion pumps that exchange potassium against intracellular H + and are temperature dependent could be the underlying pathophysiological explanation [ 1 ].…”

“…These include K + transcellular shifts, sympathetic drive with increased β-adrenergic activity and cold-induced diuresis with probable kaliuretic effect. In this issue of the journal, Boubes and colleagues [ 1 ] report an interesting case series of hypokalaemia during hypothermia and rewarming, and propose an interesting new hypothesis for the underlying mechanisms. Although the study had a limited number of subjects ( n = 4), they showed a strong correlation between serum K + level and changes in body temperature, with correlation coefficients that are >0.8 ( P < .001).…”

“…Although the study had a limited number of subjects ( n = 4), they showed a strong correlation between serum K + level and changes in body temperature, with correlation coefficients that are >0.8 ( P < .001). They discuss possible explanatory mechanisms and postulate that serum K + changes are explained primarily by transcellular K + shifts that are mediated through temperature-sensitive K + exit channels [ 1 ]. In this article, we aim to put their findings into perspective.…”