Cooling rate for triage decisions should exclude post-extrication cooling in avalanche victims

Abstract

In a recent letter, Pasquier et al.1Pasquier M. Moix P.A. Delay D. Hugli O. Cooling rate of 9.4 °C in an hour in an avalanche victim.Resuscitation. 2015; 93: e17-e18Abstract Full Text Full Text PDF PubMed Scopus (10) Google Scholar present a highly interesting case of suspected severe hypothermia after complete avalanche burial of 35 min. The patient was resuscitated and transported to a hospital with extracorporeal rewarming facilities according to international recommendations.2Brugger H. Durrer B. Elsensohn F. et al.Resuscitation of avalanche victims: evidence-based guidelines of the international commission for mountain emergency medicine (ICAR MEDCOM): intended for physicians and other advanced life support personnel.Resuscitation. 2013; 84: 539-546Abstract Full Text Full Text PDF PubMed Scopus (122) Google Scholar CPR was performed continuously until extracorporeal rewarming, but the patient did not survive and irreversible hypothermia was suspected as the cause of death. Core temperature (28.4 °C) was measured pre-hospitally in the esophagus, as recommended,3Strapazzon G. Procter E. Paal P. Brugger H. Pre-hospital core temperature measurement in accidental and therapeutic hypothermia.High Alt Med Biol. 2014; 15: 104-111Crossref PubMed Scopus (56) Google Scholar though two aspects of the case should be interpreted cautiously. Firstly, the cooling rate (9.4 °C h−1) was calculated from the time between burial and the first core temperature measurement at 55 min after burial. This not only assumes an initial core temperature of 37 °C (which would depend on the degree of physical exertion, sweating, clothing, hypoglycaemia, etc.), but also includes post-extrication cooling when the patient was exposed to low ambient temperature (−12 °C) and received cardiopulmonary resuscitation by companions and 12 min later by an ALS team, likely without measures to prevent further heat loss. Thus, this reported overall cooling rate does not differentiate the degree of cooling during burial from that after extrication. Previous studies have shown that the cooling rate during burial is lower than after extrication,4Grissom C.K. McAlpine J.C. Harmston C.H. et al.Hypercapnia effect on core cooling and shivering threshold during snow burial.Aviat Space Environ Med. 2008; 79: 735-742Crossref PubMed Scopus (21) Google Scholar, 5Locher T.H. Walpoth B.H. [Differentialdiagnose des Kreislaufstillstands hypothermier Lawinenopfer: retrospektive Analyse von 32 Lawinenunfällen.].Schweiz Rundsch Med (Prax). 1996; 85: 1275-1282PubMed Google Scholar and we suspect this would have been true also in this case with the victim buried at a depth of 1 m. Therefore, the time until the victim's core temperature was 32 °C is likely too short because it was estimated with the overall cooling rate. Secondly, the victim had no vital signs at extrication (by companions) 35 min after initial burial, when a higher core temperature is expected, and was asystolic 47 min after burial, which seems to implicate asphyxia rather than hypothermia as the cause of death. The highest cooling rate previously reported (9 °C h−1) was measured at extrication in a patient with stable circulation and a carotid pulse.6Oberhammer R. Beikircher W. Hörmann C. et al.Full recovery of an avalanche victim with profound hypothermia and prolonged cardiac arrest treated by extracorporeal re-warming.Resuscitation. 2008; 76: 474-480Abstract Full Text Full Text PDF PubMed Scopus (102) Google Scholar Such cases suggest that cooling may indeed be rapid in some patients; however, until we can reliably distinguish temperature profiles during burial and subsequent interventions, estimated cooling rates are still biased by measurement site, environmental conditions, clinical status (e.g. degree of circulation) and interventions (e.g. preventive measures against further cooling). This report emphasizes, however, the importance of prompt and accurate core temperature measurement at extrication to guide treatment decisions according to recommendations. No conflict of interest to declare.