Journal of the American Medical
October 28, 1992
and Emergency Cardiac Care
Emergency Cardiac Care Committee
American Heart Association.
Emergency Cardiac Care Committee
Richard E. Kerber, MD, Chair
Joseph P. Ornato, MD, Vice Chair
Donald D. Brown, MD
Leon Chameides, MD
Nisha Chibber Chandra, MD
Richard 0 Cummins, MD, MPH
Mary Fran Hazins MSN, RN
Richard J. Melker, MD, Ph.D.
W. Douglas Weaver, MD
Organizations Endorsing the 1992 ECC
American Academy of Pediatrics
American College of Emergency Physicians
American Red Cross
European Resuscitation Council
Heart and Stroke Foundation of Canada
National Heart, Lung, and Blood Institute
Severe accidental hypothermia (body temperature
below 30°C (86°F]) is associated with marked depression of cerebral blood flow and
oxygen requirement, reduced cardiac output, and decreased arterial pressure. Victims can
appear to be clinically dead because of marked depression of brain and cardiovascular
function, but full resuscitation with intact neurological recovery is possible, although
unusual. The victim's peripheral pulses and respiratory efforts may be difficult to
detect, but lifesaving procedures should not be with held
based on clinical presentation.
Basic Life Support
If the victim is not breathing, rescue breathing
should be initiated. Cardiopulmonary resuscitation (CPR) in the pulse-less patient should
be begun immediately, although pulse and respirations may need to be checked for longer
periods to detect minimal cardiopulmonary efforts. The traditional recommendation that
pulse and respiration's be checked for 1 to 2 minutes before beginning CPR is probably
excessive. A span of 30 to 45 seconds should be adequate to confirm pulselessness or
profound bradycardia, for which CPR would be required. It is important to prevent further
heat loss from the patient's body core by removing wet garments from the victim,
insulating the victim, shielding him or her from wind, and
ventilating with warm, humidified oxygen. For victims
not in cardiac arrest with temperatures of 30°C to 34°C (86°F to 93°F), apply
external warming devices to truncal areas only (warm packs to neck, armpits, and groin).
After stabilization, cautiously ready the patient for transport to a hospital.
Treatment of severe hypothermia (temperature less
than 30°C (86°F) in the field remains controversial.
Many providers do not have the equipment or time to
adequately assess core body temperature or to institute rewarming with warm, humidified
oxygen or warm fluids, although these methods should be initiated when available to help
prevent temperature after-drop.
Cardiac monitoring and intravenous access should
be rapidly established if possible, and core temperature should be determined in the field
with either tympanic membrane sensors or rectal probes, but none of these should delay
transfer. Airway management and transportation should be undertaken as gently as possible
to avoid precipitating ventricular fibrillation (VF). The patient should be moved in the
horizontal position to avoid aggravating hypotension through orthostatic mechanisms.
If the hypothermic victim is in cardiac arrest,
the treatment algorithm in Fig 2 should be followed. If VF is detected, emergency
personnel should deliver three shocks to determine fibrillation responsiveness. If VF
persists after three shocks, further shocks should be avoided until after rewarming to
above 30Ã�ï¿½Ã¯Â¿Â½Ã�Â¯Ã�Â¿Ã�Â½Ã�ï¿½Ã¯Â¿Â½Ã�ï¿½Ã�Â° C (86Ã�ï¿½Ã¯Â¿Â½Ã�Â¯Ã�Â¿Ã�Â½Ã�ï¿½Ã¯Â¿Â½Ã�ï¿½Ã�Â° F). CPR, rewarming, and rapid transport should immediately follow the
three defibrillation attempts. If core temperature is below 30°C (86°F), successful
defibrillation may not be possible until rewarming is accomplished.
Figure below presents a recommended
hypothermia treatment algorithm, with recommended actions that should be taken for all
possible victims of hypothermia.
Advanced Cardiac Life Support
In the hypothermic victim who has not yet
developed cardiac arrest, many physical manipulations (including endotracheal or
nasogastric intubation, temporary pacemaker, or pulmonary artery catheter insertion) have
been reported to precipitate VF. However, when specifically and urgently indicated, such
procedures should not be withheld. In a prospective multicenter study of hypothermia
victims, careful endotracheal intubation did not result in a single incident of VF.
Endotracheal intubation to provide effective ventilation with
warm, humidified oxygen
and to prevent aspiration should be performed in the
unconscious hypothermic patient with inadequate ventilation.
In such cases, prior ventilation with 100% oxygen via bag-valve mask is recommended.
Conscious victims who are cold with only mild
symptoms of hypothermia may be rewarmed with
external active and passive rewarming techniques (e.g., warm packs, warmed sleeping bags,
and warm baths).
Management of cardiac arrest due to hypothermia
is quite different from management of normothermic arrest. The hypothermic heart may be
unresponsive to cardioactive drugs, pacemaker stimulation, and defibrillation, and drug
metabolism is reduced. Administered medications, including epinephrine,
lidocaine, and procainamide, can accumulate to toxic levels if used repeatedly in the severely
rewarming techniques are the primary therapeutic modality in hypothermia victims
in cardiac arrest or unconscious with a slow heart rate.
If the patient fails to respond to initial
defibrillation attempts or initial drug therapy, subsequent defibrillation's or additional
boluses of medication should be avoided until the core temperature rises above 30Ã�ï¿½Ã¯Â¿Â½Ã�Â¯Ã�Â¿Ã�Â½Ã�ï¿½Ã¯Â¿Â½Ã�ï¿½Ã�Â° C
(86Ã�ï¿½Ã¯Â¿Â½Ã�Â¯Ã�Â¿Ã�Â½Ã�ï¿½Ã¯Â¿Â½Ã�ï¿½Ã�Â° F). Bradycardia may be physiological in severe hypothermia, and cardiac pacing is
usually not indicated unless bradycardia persists after rewarming. The temperature at
which defibrillation should first be attempted and how often it should be tried in the
severely hypothermic patient have not been firmly established. There are also conflicting
reports about the efficacy of bretylium tosylate in this setting, although it may prove
helpful in VF by raising the fibrillation threshold.
Treatment of severely hypothermic victims in
cardiac arrest in the hospital setting should be directed at rapid core
rewarming. Techniques that can be used include the administration of heated,
humidified oxygen (42°C to 46°C (108.7 to 115°F), warmed intravenous fluids (normal
saline) at 43°C (109°F) infused centrally at rates of approximately 150 to 200
(to avoid over-hydration),
peritoneal lavage with warmed (43°
C [109°F]) potassium-free fluid administered 2 L at a time, or extracorporeal blood
warming with partial bypass. The use of esophageal rewarming tubes in the United States
has not yet been reported, although they have been used extensively in Europe. Pleural
lavage with warm saline instilled through a chest tube has also been used successfully.
The routine administration of steroids, barbiturates, or antibiotics has not been
documented to help increase survival or decrease postresuscitative damage.