Human physiological adaptations to acute cold exposure

David BartonOctober 2, 2014University of Pittsburgh School of Medicine

Outline

•Thermal homeostasis

•Behavioral adaptations

•Physiological adaptations

General adaptation syndrome

How low is too low?

Brooks et al., 2005

Temp Regulation

Hammel et al., 1959

Sleep at 5 °C

“Although certain features of this sleeping chamber were objectionable to the natives it proved to be entirely adequate for maintaining a suitable cold exposure.”

Balance of heat gain/loss

Brooks et al., 2005

Radiative heat lossRespirationInsensible water lossUrination

Normal Thermoregulation

Pozos and Danzl, 2002

Types of adaptations

•Behavioral

•Physiological

Behavioral adaptations

• Prevent physiological adaptation from needing to occur (usually)

Clothing

FireShelter

ClothingBody

Insulative air pocket

Physiological adaptations

•Insulative

•Metabolic

Insulative adaptation

•Cutaneous vasoconstriction

•Skin fold thickness

•Fat/muscle insulation

Thompson-Torgerson et al., 2007

Tloc, local skin temperature.

Skin

blo

od fl

ow

Cutaneous vasoconstriction

Infrared scan of the palmar hand surface. Blue, 43° C (109.4° F); red, 68° C (154.4° F). A, At room temperature. B, After 5 minutes in a cold room, with evidence of vasoconstriction.

Auerbach, Wilderness Medicine

Cui et al., 2005Skin suit with 34 or 16 °C water

Cardiac output (CO) = Stroke volume + Heart rate

Wagner and Horvath, 1985

Cold-induced diuresis

Budd and Warhaft, 1966

Segar and Moore, 1968

*Renal blood flow decreases 50% at 27-30 °C

Cold-induced cutaneous vasoconstriction is mediated by Rho kinase in vivo in human skin

Tloc, local skin temperature.

Skin

blo

od fl

ow

Thompson-Torgerson et al., 2007

Effect of cooling (to 28°C) on Rho activity in human cultured dermal arteriolar VSM cells.

Bailey et al., 2004

Hunting reflex

Physiological adaptations

•Insulative

•Metabolic

Metabolic adaptation

•Shivering (and pre-shivering) response

•Non-shivering thermogenesis

Metabolic adaptation

•Shivering (and pre-shivering) response

•Non-shivering thermogenesis

Budd and Warhaft, 1966

Exposure to 10°C

Petajam and Williams, 1972

Shivering response

Shivering yields heat production

Madden et al., 2013

Shivering is mediated by α2-adrenoreceptors

Metabolic adaptation

•Shivering (and pre-shivering) response

•Non-shivering thermogenesis

Young et al., 1986

Increased metabolic rate90 min at 5°C

How does norepinephrine cause this?

Golozoubova et al., 2006

Cannon, 2011

Brown-Adipose-Tissue Activity as Assessed by PET–CT with 18F-FDG.

van Marken Lichtenbelt WD et al. N Engl J Med 2009;360:1500-1508.

Metabolic energy sources•From fats

•Also from usual sources:▫Carbohydrates, especially glycogen stores▫Protein

•Can cause hypoglycemia decompensation

Havel and Goldfien, 1959

Special considerations

•Some groups cannot adapt as well▫Age extremes▫Disease states▫Alcohol/drugs

•Risk factors for death from accidental hypothermia: ethanol use, homelessness, psychiatric disease, and older ageCDC, 2005

Mareedu et al., 2008

Mareedu et al., 2008

ReferencesBrooks GA, Fahey TD, and Baldwin KM. Exercise physiology: human bioenergetics and its applications. New York:

McGraw-Hill, 2005.Budd GM, and Warhaft N. Body temperature, shivering, blood pressure and heart rate during a standard cold stress in

Australia and Antarctica. J Physiol 186: 216-232, 1966.Cannon B, and Nedergaard J. Nonshivering thermogenesis and its adequate measurement in metabolic studies. J Exp

Biol 214: 242-253, 2011.Centers for Disease Control and Prevention. Hypothermia-related deaths-United States, 2003-2004. MMWR 54:173,

2005.Cui J, Durand S, Levine BD, and Crandall CG. Effect of skin surface cooling on central venous pressure during

orthostatic challenge. Am J Physiol Heart Circ Physiol 289: H2429-2433, 2005.Golozoubova V, Cannon B, and Nedergaard J. UCP1 is essential for adaptive adrenergic nonshivering thermogenesis.

Am J Physiol Endocrinol Metab 291: E350-357, 2006.Hammel HT, Elsner RW, Le Messurier DH, Andersen HT, and Milan FA. Thermal and metabolic responses of the

Australian aborigine exposed to moderate cold in summer. Journal of Applied Physiology 14: 605-615, 1959.Hillier AP. Thyroxine deiodination during cold exposure in the rat. J Physiol 197: 135-147, 1968.Lewis T. Observations upon the reactions of the vessels of the human skin to cold. Heart 15: 177-208, 1930.Madden CJ, Tupone D, Cano G, and Morrison SF. alpha2 Adrenergic Receptor-Mediated Inhibition of Thermogenesis. J

Neurosci 33: 2017-2028, 2013.Mareedu RK, Grandhe NP, Gangineni S, Quinn DL. Classic EKG changes of hypothermia. Clin Med Res 6:107-8, 2008.Petajan JH, and Williams DD. Behavior of single motor units during pre-shivering tone and shivering tremor. Am J Phys

Med 51: 16-22, 1972.Pozos RS, and Danzl DF. Human physiological responses to cold stress and hypothermia. In: Medical Aspects of Harsh

Environments, Volume 1, edited by Pandoff KB, and Burr RE. Washington, DC: Office of the Surgeon General, U.S. Army, 2002.

Segar WE, and Moore WW. The regulation of antidiuretic hormone release in man: I. Effects of change in position and ambient temperature on blood ADH levels. J Clin Invest 47: 2143-2151, 1968.

Thompson-Torgerson CS, Holowatz LA, Flavahan NA, and Kenney WL. Cold-induced cutaneous vasoconstriction is mediated by Rho kinase in vivo in human skin. Am J Physiol Heart Circ Physiol 292: H1700-1705, 2007.

Wagner JA, and Horvath SM. Cardiovascular reactions to cold exposures differ with age and gender. J Appl Physiol 58: 187-192, 1985.

Young AJ, Muza SR, Sawka MN, Gonzalez RR, and Pandolf KB. Human thermoregulatory responses to cold air are altered by repeated cold water immersion. J Appl Physiol 60: 1542-1548, 1986.

Questions?