DROWNING - Medicine for Mountaineering and Other Wilderness Activities - page 433

tion and the performance in a maze are much better when ten minutes of ischemia occurs
at a brain temperature of 86°F (30°C) instead of 99°F (37°C).
Various findings indicate that when the brain cools only 5.4° to 9°F (3° to 5°C), it is
protectedmorethanwouldbepredictedfromdecreasedcerebralmetabolicoxygenrequire-
ments alone. Furthermore, even though the mammalian dive reflex in humans has limited
or no effectiveness, any cold-induced circulatory adjustments would favor conservation of
oxygen for the heart and brain. Finally, cold water ventilation could accelerate brain cool-
ing and provide further protection.
These conclusions are supported by the limited number of adult case reports available.
Three individuals aged twenty-one to thirty-one years were submersed for seventeen to
twenty-five minutes and were admitted to the hospital with rectal temperatures ranging
from73°to90°F(23°to32°C).Allwereresuscitated andrewarmed successfully.Foreach
of these individuals, submersion times were almost double (triple in the warmest person)
thesurvivaltimespredictedbythetemperature/cerebralmetabolicoxygenrequirementsre-
lationship.
Theseincidentsimplicate oneorbothofthefollowingmechanisms: theexistence ofad-
ditional protective cooling mechanisms, or selective cooling of the brain below the meas-
ured rectal temperatures. This cooling could be the result of ventilation of cold water with
limiting of the cooling to central organs (heart, lungs and brain), not peripheral tissues. Al-
ternatively, direct conductive cooling of the brain by cold water could have occurred fol-
lowing cardiac arrest.
Theskierdescribedafewpagesbackencounteredcircumstancesthathelpedhersurvive
and complete her training as a physician. Brain cooling is necessary for surviving such a
long anoxic insult, but both the degree of cooling and the speed of cooling are protective.
This young lady's face was in an air pocket that allowed her to continue breathing for her
first forty-five minutes under the ice. During this time she became very hypothermic. As
a result her brain was already cold when she became unconscious and drowned, which
helped her survive such a long subsequent period of anoxia.
PRESENTATION OF SURVIVORS
Individuals who have drowned and have been successfully resuscitated present with a
spectrum of findings that range from a totally normal, asymptomatic appearance to severe
distress. The heart rate may be normal or rapid and weak. An abnormal rhythm may be
present.Pulmonaryfindingsrangefromnormaltoshortnessofbreath,cyanosis(bluishdis-
coloration of the skin, lips, and nails), wheezing, crackling sounds heard when listening to
the chest, and profound respiratory distress. Neurologic findings range from an alert and
oriented person to one who is combative, stuporous, or comatose.