title: Myocardial mechanical dysfunction and calcium overload following rewarming from experimental hypothermia in vivo.
abstract: Rewarming patients from accidental hypothermia are regularly complicated with cardiovascular instability ranging from minor depression of cardiac output to fatal circulatory collapse also termed "rewarming shock". Since altered Ca2+ handling may play a role in hypothermia-induced heart failure, we studied changes in Ca2+ homeostasis in in situ hearts following hypothermia and rewarming. A rat model designed for studies of the intact heart in a non-arrested state during hypothermia and rewarming was used. Rats were core cooled to 15 degrees C, maintained at 15 degrees C for 4h and thereafter rewarmed. As time-matched controls, one group of animals was kept at 37 degrees C for 5h. Total intracellular myocardial Ca2+ content ([Ca2+]i) was measured using 45Ca2+. Following rewarming we found a significant reduction of stroke volume and cardiac output compared to prehypothermic control values as well as to time-matched controls. Likewise, we found that hypothermia and rewarming resulted in a more than six-fold increase in [Ca2+]i to 3.01+/-0.43 micromol/g dry weight compared to 0.44+/-0.05 micromol/g dry weight in normothemia control. These findings indicate that hypothermia-induced alterations in the Ca2+-handling result in Ca2+ overload during hypothermia, which may contribute to myocardial failure during and after rewarming.
authors.affiliation: Department of Anaesthesiology, Institute of Clinical Medicine, University of Tromsø, 9037 Tromsø, Norway. Timofey.Kondratiev@fagmed.uit.no
authors.forename: Timofei V
authors.initials: TV
authors.lastname: Kondratiev
authors.forename: Ragnhild M
authors.initials: RM
authors.lastname: Wold
authors.forename: Ellen
authors.initials: E
authors.lastname: Aasum
authors.forename: Torkjel
authors.initials: T
authors.lastname: Tveita
mesh_terms: D000818:Animals; D002118:Calcium / Q000502:physiology*; D002302:Cardiac Output; D006321:Heart / Q000502:physiology*; D006333:Heart Failure / Q000209:etiology; D006439:Hemodynamics; D006706:Homeostasis; D007036:Hypothermia, Induced; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D017694:Rewarming
chemical_list: D002118:Calcium