presented by Mel Herbert, MD
edited by Veronica Vasquez, MD
There are a multitude of definitions and cut-off values for the varying degrees of hypothermia. Mild hypothermia (34 - 35C or 93.2 -95F) is considered the excitation phase wherein shivering occurs and cardiac output increases. In moderate hypothermia (30 - 34C or 86 – 93.2F) the adynamic phase, cardiac output begins to drop. This progresses to the complete cardiovascular shutdown seen in severe hypothermia (30C. All medications should be withheld until temperature is >30°C via active internal rewarming. Extracorporeal membrane oxygenation (ECMO) provides rapid rewarming, increasing core temperature by 1-2C every 15 minutes. If ECMO is unavailable, other modalities of internal rewarming should be performed including peritoneal lavage and pleural lavage with warm saline through chest tubes. Providers ought to be aware of rewarming phenomenon such as “afterdrop,” theorized to occur upon rewarming of peripheral tissues. Vasodilatation causes cooler blood in the extremities to circulate to the body core, averaging out to a cooler body temperature overall. Lastly, a patient is not dead until they are “warm and dead” at 32C (92F), considering a higher threshold in pediatric patients with a more responsive myocardium.
-Circulation 2005;112;IV-136-IV-138; originally published online Nov 28, 2005
-This month’s pearl comes from Dr. Nicholas Testa’s Grand Rounds talk at USC
to find more EM:RAP educational materials, go to www.emrap.org