DROWNING - Medicine for Mountaineering and Other Wilderness Activities - page 427

suffer vocal cord spasm and cannot aspirate water, which account for approximately 15
percent of all drownings.
Cold shock is the most common cause of drowning in water colder than approximately
50°F (10°C) and affects both the respiratory and cardiac systems. Upon immersion in such
cold water gasping occurs, may be uncontrollable, and lasts approximately one minute.
Lack of understanding of this phenomenon may result in panic and the aspiration of more
water unless the head is kept above water.
The sudden cooling of the skin results in increased peripheral vascular resistance of su-
perficial blood vessels. The heart rate and cardiac output increase. The outpouring of cat-
echolamines (epinephrine and related hormones) increases the risk for fatal cardiac arrthy-
mias. Hyperventilation causes the loss of carbon dioxide and metabolic alkalosis. The sub-
sequent decrease in cerebral blood flow can result in disorientation.
In witnessed drownings, individuals typically pass through three stages ( Table 28-1 ) .
The first is characterized by panic and struggling, often portrayed as flailing with the arms.
The person is trying to swim and often is coughing, sputtering, and calling for help.
Thesecondstageischaracterized bybreathholdingortheabsenceofbreathing(apnea).
The individuals swallow large amounts of water and often vomit. During this stage they
aspirate water if laryngospasm is not present. They may aspirate gastric contents if they
vomit, which can produce serious lung damage.
During the third stage the individual loses consciousness. The airway reflexes are lost
and coughing no longer occurs. Agonal respirations may move some water into and out of
the lungs. Seizures may occur as the result of cerebral hypoxia. Eventually anoxia leads to
ventricular fibrillation or cardiac arrest.
In cold water local cooling decreases nerve conduction and muscle control becomes un-
coordinated and inefficient. After approximately ten minutes of cold water immersion, any
reasonable attempt at swimming or self-rescue becomes almost impossible. At this point
individuals who do not have flotation devices or a source of support such as clinging to
surface ice usually drown. (They do not die from hypothermia.)
Persons who are supported with the head above water lose consciousness as the result
ofhypothermia inabout anhour.However,they donotdie fromhypothermia until approx-
imately two hours have elapsed.