COLD INJURIES - Medicine for Mountaineering and Other Wilderness Activities - page 403

Cold Shock Response
Suddenimmersionintocoldwaterstimulatesoneormorelargeinspiratorygasps,which
is usually followed by hyperventilation and also may be associated with a substantial in-
crease in blood pressure and heart rate. Individuals with cardiac disease may experience
cardiacarrestorventricularfibrillation.Iftheheadissubmerged,thegaspreflexcouldres-
ult in aspiration of water and immediate drowning.
Subsequent hyperventilation usually diminishes within seconds to minutes but could be
exaggerated and prolonged by emotional stress and panic. Uncontrolled hyperventilation
makes coordinating breathing with swimming strokes very difficult, which could lead to
drowning.Theoretically,coldshockcanoccurinwaterwarmerthan68°F(20°C),although
these effects are more life threatening at temperatures below 59°F (15°C) and worsen as
water temperature decreases.
The best way to minimize cold shock is to enter cold water in a slow and controlled
manner and to keep the head from being submersed. Individuals should focus on getting
through the first minute, suppressing panic, and consciously getting breathing under con-
trol. Once breathing is controlled, individuals usually have time to evaluate the situation
and make proper survival choices.
Cold Incapacitation
When exposed to cold, the body attempts to preserve a normal core temperature of
98.6°F(37°C)bydecreasingheatloss.Constrictionofthebloodvesselsinthelimbsshunts
blood from the extremities to the core and decreases heat loss through the limbs, but this
allows limb tissues to cool rapidly. The intense cooling of muscle and nerve tissues results
in muscular failure, and the individual progressively loses the ability to swim, to maintain
postureinthewater,ortousethehandstoperformothersurvivaltasks.Inwaternearfreez-
ing, incapacitation can occur within five to ten minutes but takes progressively longer at
higher water temperatures.
Once physical strength and dexterity start to diminish, the trend continues and does not
reverse itself. Therefore, the best course of action must be determined promptly and fol-
lowed immediately. Such actions could include the following:
◆ Pulling oneself out of the water, or inflating and boarding a life raft
◆ Getting as much of the body as possible out of the water and onto a floating object
◆ Ensuring flotation by inflating a personal flotation device (PFD), which should have
been put on before entering the water
◆ Attracting assistance
Executing these actions while the cold shock responses predominate may be difficult.
However, once breathing is under control, immediate action should be taken. If self-rescue
is not possible, actions to minimize heat loss ( Fig. 26-2 ), such as assuming the H.E.L.P