Can you catch hypothermia without frostbite in temperatures of 3 degrees centigrade, if you wear gloves a ski mask and hat but only a shirt or pull over?
Short Answer: Yes.Long Answer: Buckle Up.Keeping it simple and in wilderness medicine framework, I’ll talk about just two forms of hypothermia (I’ll leave out other common forms such as iatrogenic and theraputic); Accidental (aka Primary) and Trauma Induced (aka Metabolic). Hypothermia is, at its essence, a thermoregulation problem and, by definition, Accidental Hypothermia (to what you are referring in your question- being outside and getting cold) is determined when the body’s core temperature drops below 35deg C (95dec F) *1,2.From Wilderness Medical Society Practice Guidelines for the Out-of-Hospital Evaluation and Treatment of Accidental Hypothermia: 2014 Update *1:Hypothermia occurs as a result of net heat loss from the body. Heat can be lost or gained by conduction, convection, and radiation and lost through evaporation. Conduction is the direct transfer of heat from warmer to cooler objects that are in contact with each other. Convection is the transfer of heat to or from a gas or a liquid that is in motion. Radiation is the transfer of heat in the form of electromagnetic energy between 2 objects that are visible to each other. Evaporation is the loss of heat by vaporizing liquid—usually water—in sweat, on the skin, or in clothing, or from insensible losses from the skin or from respiration.The human body attempts to maintain a core temperature of 371C 0.51C. The thermoregulatory control center in the hypothalamus receives input from central and peripheral thermal receptors. The integrated thermal signal triggers autonomic reflexes that control whether cooling responses, such as vasodilation or sweating, or warming responses, such as vasoconstriction or shivering, are initiated.1 Peripheral blood flow is also partly regulated by local skin temperature.You can get hypothermic in 21C (70F) weather in the tropics if you, say, get drunk and fall asleep on sand wearing wet clothes in a light breeze (conduction, convection, evaporation forms of heat loss and a slowed metabolic rate with no external heat source).As a firefighter, we have a lot of frozen bodies of water in our district and ice rescue teams within the department; people who break through the ice may, depending upon clothing, fitness, temp, etc, begin experiencing hypothermia within minutes, frostbite can set in after hypothermia takes hold.Metabolic Hypothermia, on the other hand, is a result of the body’s response to trauma- called Trauma Induced Hypothermia (TIH)- and is something which has been identified in the past decade with advances in austere medicine coming out of the Afghanistan and Iraq wars, and it can occur in 38C temps in trauma patients. Whereas Accidental Hypothermia sets in at 35C, TIH occurs due to metabolic factors and sets in at a body core temperature of just 36C (a full degree sooner) following a traumatic injury*2. As a result, in backcountry medicine one of the first things we do is wrap a trauma patient in a blanket of some kind (sleeping bag, emergency/”space” blanket, etc) to address this concern.So, can you “catch” hypothermia in 3C (37F) weather without getting frostbite, regardless of what you are wearing? Absolutely. The two, while not mutually exclusive, are not necessarily congruous either, nor are they necessarily progressive or resultant.Ken Zafren, MD; Gordon G. Giesbrecht, PhD; Daniel F. Danzl, MD; Hermann Brugger, MD; Emily B. Sagalyn, MD, MPH; Beat Walpoth, MD; Eric A. Weiss, MD; Paul S. Auerbach, MD; Scott E. McIntosh, MD, MPH; Ma?ria Ne?methy, MD; Marion McDevitt, DO, MPH; Jennifer Dow, MD; Robert B. Schoene, MD; George W. Rodway, PhD, APRN; Peter H. Hackett, MD; Brad L. Bennett, PhD; Colin K. Grissom, MD. Wilderness Medical Society Practice Guidelines for the Out-of-Hospital Evaluation and Treatment of Accidental Hypothermia: 2014 Update. WILDERNESS & ENVIRONMENTAL MEDICINE, 25, S66–S85 (2014)Brad L. Bennett, PhD, EMT-P, FAWM; John B. Holcomb, MD. Battlefield Trauma-Induced Hypothermia: Transitioning the Preferred Method of Casualty Rewarming. WILDERNESS & ENVIRONMENTAL MEDICINE, 28, S82–S89 (2017)