• Nirav G Shah, Mark J Cowan, Edward Pickering, Houtan Sareh, Majid Afshar, Dawn Fox, Jennifer Marron, Jennifer Davis, Keith Herold, Carl B Shanholtz, and Jeffrey D Hasday.
• Pulmonary and Critical Care Medicine Division, Department of Medicine and the General Clinical Research Center, University of Maryland School of Medicine, and the Baltimore VA Medical Center, MD 21201, USA.
• J Crit Care. 2012 Dec 1; 27 (6): 746.e1-8.

PurposeThis study had 2 objectives: (1) to quantify the metabolic response to physical cooling in febrile patients with systemic inflammatory response syndrome (SIRS) and (2) to provide proof for the hypothesis that the efficiency of external cooling and the subsequent shivering response are influenced by site and temperature of surface cooling pads.MethodsTo quantify shivering thermogenesis during surface cooling for fever, we monitored oxygen consumption (VO(2)) in 6 febrile patients with SIRS during conventional cooling with cooling blankets and ice packs. To begin to determine how location and temperature of surface cooling influence shivering, we compared 5 cooling protocols for inducing mild hypothermia in 6 healthy volunteers.ResultsIn the patients with SIRS, core temperature decreased 0.67 °C per hour, all patients shivered, VO(2) increased 57.6%, and blood pressure increased 15% during cooling. In healthy subjects, cooling with the 10 °C vest was most comfortable and removed heat most efficiently without shivering or VO(2) increase. Cooling with combined vest and thigh pads stimulated the most shivering and highest VO(2) and increased core temperature. Reducing vest temperature from 10 °C to 5 °C failed to increase heat removal secondary to cutaneous vasoconstriction. Capsaicin, an agonist for the transient receptor potential cation channel subfamily V member 1 (TRPV1) warm-sensing channels, partially reversed this effect in 5 subjects.ConclusionsOur results identify the hazards of surface cooling in febrile critically ill patients and support the concept that optimization of cooling pad temperature and position may improve cooling efficiency and reduce shivering.Copyright © 2012 Elsevier Inc. All rights reserved.

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