Page 126 - 2020 JSOM Winter

improved clothing ensembles, 9,10 and leadership emphasis on skin tissues. Chilblains (also called pernio) is a more serious
18
cold-injury prevention. Nonetheless, cold-weather injuries condition associated with repeated exposure to near-freezing,
11
still occur, and there are reasons to assume that military op- dry environmental conditions. Individuals experience burning
erations in colder areas of the world might increase. Climate sensations, pruritus, swelling, and erythema. Blisters and ul-
change has resulted in the melting of arctic ice. There will cerations may occur in more severe cases. 18–20 Histologic stud-
12
likely be competition for natural resources in Arctic areas, ies indicate inflammatory infiltrates (mainly lymphocytes),
including oil reserves that were previously inaccessible and necrotic keratinocytes, and microthrombi in the dermis. 19
where national boundaries are not clearly delineated. Sea lanes
across the Arctic Ocean are opening, and their use can reduce Frostbite is the most serious injury on this spectrum. It occurs
ocean transit times and avoid Panama Canal and Suez Canal when body tissues are exposed to temperatures below freez-
fees, but these areas are largely in Russian territory. 13,14 These ing and the tissues are damaged through direct and indirect
facts increase the likelihood that US forces will be deployed to mechanisms associated with freezing body fluids. Lower tem-
colder areas of the world for peacekeeping, handling of natu- peratures, wind, and moisture exacerbate this process. Patho-
21
ral disasters, and other national security operations. It is ex- physiologic changes are depicted in Figure 1 and involve two
pected that cold-weather training operations will increase and different mechanisms: (1) direct cellular damage and (2) effects
that the United States will partner with coalition allies in these from vascular inflammation, thrombosis, and ischemia. 15,22
efforts. Medical personnel planning for cold-weather opera- When peripheral tissues (e.g., fingers, toes, ears, nose) are
14
tions should emphasize cold-injury prevention and prepare for first exposed to cold temperatures, they respond with cycles
the treatment of cold-related injuries. of vasoconstriction and vasodilation. Cold-induced vasodi-
lation (CIVD) warms the tissue by allowing blood from the
Among the most serious cold weather–related injuries is frost- warmer body core to enter the peripheral circulation, while
bite. Low temperature exacerbated by wind and surface mois- vasoconstriction promotes cooling. When heat loss is great
ture results in body cooling and the shunting of blood away enough, the vasodilation/vasoconstriction cycles cease, and ice
from the extremities. If the blood flow to the extremities is crystals begin to form in the extracellular fluids. This increases
restricted long enough and skin temperatures fall low enough, osmotic pressure and draws free water from cellular spaces,
ice crystals will form in the blood, and tissues will freeze. resulting in intracellular dehydration, hyperosmolality, de-
Frostbite will occur, with the resulting tissue necrosis and the creased pH, and denaturing of lipids and proteins that damage
potential for catastrophic amputation in the affected parts. 15,16 cell membranes and result in cellular necrosis. Ice crystals also
This article covers the pathophysiology, epidemiology, diagno- mechanically damage cell membranes and slow blood flow.
sis, treatment, and prevention of frostbite. These factors initiate an inflammatory response and release
of the inflammatory mediators (prostaglandins, thromboxane,
bradykinin, histamine) that cause platelet and leukocyte ag-
Pathophysiology
gregation and thrombosis in affected tissue, leading to isch-
Frostbite is part of a spectrum of cold temperature–induced emia and cell death. 17,21–23
local injury that ranges from minimal chilling of the skin with-
out impairment to major tissue damage from the development Once exposed to a warmer environment, vasodilation re-
of extracellular ice crystals. Frostnip is the least severe con- sumes, resulting in reperfusion injury and a further increase in
17
dition on this spectrum. Frostnip generally involves a drop in the inflammatory response. The thin layer of endothelial cells
the local temperature of the epidermal and dermal skin layers, separates from blood vessels. Capillary leakage from damaged
with some local pain and/or numbness but no injury to the endothelial cells can form epidermal blisters. An increase in the

FIGURE 1 Pathophysiology of frostbite.

124 | JSOM Volume 20, Edition 4 / Winter 2020