DROWNING - Medicine for Mountaineering and Other Wilderness Activities - page 430

◆ A five-year-old boy fell into the waters of a frozen lake and was submerged for forty
minutes. Upon arrival at the hospital his temperature was 75.2°F (24°C). He survived
neurologically intact.
◆ Athree-year-oldgirlwasadmittedtoahospitalafterdrowningwithacoretemperature
of 65.1°F (18.4°C). After rewarming on cardiopulmonary bypass, she survived and
had no neurologic deficits twenty months later.
◆ A seven-year-old boy fell into a culvert and was found fifteen minutes later. His tem-
peraturewas80.6°F(27°C).Afteraninitialperiodofgrossandfinemotordeficitsand
psychometric delays, he ultimately was found to be above average in school perform-
ance.
◆ The longest submersion followed by successful resuscitation to date is sixty-six
minutes. CPR was started for that two-and-one-half-year-old girl by an experienced
professional rescue team as soon as she was retrieved from 41°F (5°C) water. She was
transported in minutes to a hospital that was prepared for her arrival and was immedi-
ately rewarmed with cardiopulmonary bypass.
Adults have also survived such submersion incidents. One young lady fell through the
ice of a fast-moving river while skiing. She struggled for almost forty-five minutes before
she finally became unconscious. Rescue crews required another sixty minutes to remove
her from beneath the ice. Her core temperature had fallen to 55.4°F (13°C) yet she sur-
vived. (To date, hers was the lowest core temperature resulting from accidental hypother-
mia that was followed by successful resuscitation.)
The understanding of why individuals can survive cold water submersion for as long as
sixty-six minutes with full or partial neurological recovery has been advanced by several
recent findings. Explanations for this phenomenon relate to both the mechanisms for, and
extent of, brain and body cooling that occurs, as well as the manner in which this cooling
is protective.
Mechanisms of Cooling
Foryearschildrencommonlyhavebeenthoughttohaveanadvantageincoldwatersub-
mersion incidents because their greater surface-area-to-mass ratio allows faster conduct-
ive cooling, which provides cerebral protection due to the decreased cerebral metabolic re-
quirementsforoxygen.Inaddition,themammaliandivereflexthatproducesaslowerheart
rate (bradycardia) and shunts blood flow to important core organs such as the heart and
brain was thought to be protective. A third possibility that has recently been explored is
that aspirating cold water may result in a rapid and deep cooling during submersion (acute
submersion hypothermia).
The dive reflex is elicited in diving mammals such as seals by contact of the face with
cold water and consists of breath holding, intense constriction of peripheral blood ves-
sels,bradycardia,decreasedcardiacoutput,andanincreasedmeanarterialpressure.Breath