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Glossary
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- BUN
- blood urea nitrogen
- CNS
- central nervous system
- CPR
- cardiopulmonary resuscitation
- EEG
- electroencephalogram
- IL-1β
- interleukin-1β
- NSAID
- non-steroidal anti-inflammatory drug
- PT
- prothrombin time
- PTT
- partial prothrombin time
- SSRI
- selective serotonin-reuptake inhibitor
- TNF-α
- tumor necrosis factor-α
Terms
- Afterdrop
- Paradoxical drop in core temperature that occurs during rewarming as cold blood from the cooler periphery returns to cool the core compartment can result in significant hemodynamic instability. The occurrence of this phenomenon is dependent on the magnitude of the temperature gradient between the two compartments and management of rewarming and the volume status. Rehydration of hypovolemic patients that resulted from cold-induced diuresis will decrease the risk for afterdrop.
- Conductive heat loss
- The process of heat exchange in which there is a molecular transfer of heat energy by direct contact with colder material (wet clothing, stretcher, etc.). Water conducts heat 25 times faster than air because of its greater density and, therefore, greater heat capacity. Under normal circumstances, conductive heat loss accounts for only 3% of total heat loss, but is more significant in conditions of water submersion.
- Convective heat loss
- The process of heat transfer between regions of unequal density that result from non-uniform heating. The rate of convective heat loss/gain depends on the density of the moving substance and its velocity. This phenomenon has been effectively applied using the forced-air heating blanket. Under normal circumstances, convective heat loss accounts for only 15% of total heat loss.
- Core compartment
- The body comprises two compartments for the purposes of thermoregulatory physiology, the “skin” and “core” compartments. The core compartment comprises the brain and the vital organs of the thoracic and abdominal cavities. The peripheral (shell) compartment core protects the core compartment by insulating it from the harsh, cold environment.
- Evaporative heat loss
- The process of heat transfer from water to a gas (i.e., perspiration or respiration). The rate of heat loss from the evaporation of water from the skin or respiratory tract is approximately 30 mL/h. Under normal circumstances, evaporative heat loss accounts for about 22% of total heat loss.
- Frostbite
- Localized cold-induced tissue injury in which blood vessels are severely or irreparably damaged. The markedly reduced blood flow results in vascular occlusion and thrombosis. Initially, plasma leaks from the microvasculature. Progressive freezing causes cellular death and release of vasoactive and toxic intermediates. The ischemic tissues may be further injured by minimal trauma, such as weight bearing, walking, or pressure on frostbitten areas. The final extent of damage and demarcation cannot be immediately determined, but takes weeks to months.
- Frostnip
- Modest and usually reversible form of local cold injury that tends to occur at locations farthest removed from the core (i.e., nose, cheeks, fingers, toes, hands, and feet). It is manifest by transient numbness and tingling that resolves after rewarming. This does not represent true frostbite, because no tissue destruction occurs
- Peripheral or shell compartment
- The body comprises two compartments for the purposes of thermoregulatory physiology, the “skin” and “core” compartments. The peripheral compartment (also referred to as the cutaneous compartment or shell) is the site where the most heat exchange occurs. This compartment comprises the skin, extremities, and muscles. Vascular reactivity during hypothermia directs blood away from the shell compartment to isolate the internal organs from the cold, thereby creating a temperature gradient.
- Radiant heat exchange
- The transfer of heat energy by infrared radiation from a warm object. Radiant heat loss accounts for about 60% of total heat exchange. The rate of radiant heat loss/gain is related to the magnitude of the temperature gradient and amount of exposed surface.
- Reperfusion injury
- Restoration of blood flow after a period of ischemia may result in systemic effects of the returning blood (respiratory acidosis, metabolic acidosis, hyperkalemia, hypothermia, and vasoactive metabolites) and local damage to the previously ischemic tissue (edema, local cytokine/neurotransmitter release, microvascular thrombosis, etc) that can result in progression of cell injury and death.
- Rewarming shock
- In response to rewarming, vascular dilation that leads to pooling of blood can progress to cause hypotension and hypovolemic shock.
- Thermoregulatory system
- The system comprises 1) afferent input of thermal information to the hypothalamus, and 2) efferent responses that control heat loss and production by shivering or vascular reactivity. When body temperature falls below the set point of the hypothalamus, the afferent response is to increase heat production by shivering (thermogenesis) and alter vaso-reactivity vasoconstriction to conserve core temperature by shunting blood away from the peripheral compartment.
- Trench foot or immersed foot
- An injury associated with shipwreck survivors or soldiers whose feet have been cold and wet, but not frozen. Trench foot is primarily a cold-induced injury to nerve and muscle without gross pathological changes in blood vessels or skin. The clinical picture reflects primary hypoxia. Prognosis depends on severity of tissue damage and ability to restore microcirculation in the damaged extremity. The final extent of damage and prognosis cannot be immediately determined.
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| Albert Cheung, MD has no financial relationships with pharmaceutical companies, biomedical device manufacturers, or health-care related organizations. Dmitri Guvakov, MD, PhD has no financial relationships with pharmaceutical companies, biomedical device manufacturers, or health-care related organizations. Stuart Weiss, MD, PhD has no financial relationships with pharmaceutical companies, biomedical device manufacturers, or health-care related organizations. Wenjun Martini, PhD, editorial consultant, has no financial relationships with pharmaceutical companies, biomedical device manufacturers, or health-care related organizations.
Deborah Korenstein, MD, FACP, Co-Editor, PIER, has no financial relationships with pharmaceutical companies, biomedical device manufacturers, or health-care related organizations. Richard B. Lynn, MD, FACP, Co-Editor, PIER, has no financial relationships with pharmaceutical companies, biomedical device manufacturers, or health-care related organizations. |
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Hypothermia