Evaluation and Treatment of Hypothermia, Colin K. Grissom, M.D.
page 7
5.
External auditory canal thermometers that measure infrared emission from the
tympanic membrane may be inaccurate for assessment of hypothermia.
6.
Bladder temperature is convenient if the temperature probe is built into a bladder
catheter, but may be abnormally low in the setting of a cold diuresis.
Airway Management
Airway management and providing supplemental oxygen are important in
management of hypothermia. The indications for endotracheal intubation of a
hypothermic patient are identical to those under normothermic conditions. Gentle
endotracheal intubation is safe during hypothermia (Danzl 2001; Danzl 1987). Pre-
oxygenation with 100% oxygen and assisted ventilation prior to intubation may protect
the heart. Oxygen therapy should be directed at providing oxygen hemoglobin saturations
of greater than 90%.
Hypotension
Palpation of peripheral pulses is often difficult in a vasoconstricted and
bradycardic hypothermic patient. Apparent cardiovascular collapse may actually reflect
depressed cardiac output just sufficient to meet minimal metabolic demands. Auscultate
and palpate for at least one minute to find pulses. If no pulse is palpated wait for several
minutes while supplemental oxygen and assisted ventilation are provided, then repeat
palpation for pulses. Most hypothermic patients are initially volume depleted and IV fluid
resuscitation with warmed isotonic fluids is indicated.
Arrhythmias
Cardiac arrhythmias can be a major problem in hypothermic patients.
Bradycardia and atrial fibrillation are frequent. No treatment is usually necessary because
atrial fibrillation and bradycardia will convert after rewarming. Patients with moderate or
severe hypothermia require careful handling because they are sensitive to VF and
asystole. Treatment of VF is discussed below.
Cardiopulmonary Resuscitation
Cardiopulmonary
resuscitation (CPR) with chest compressions should be initiated
on any patient with VF or asystole, and no signs of life. Three defibrillations may be tried
in patients in VF or asystole. If unsuccessful, then the patient should be warmed before
further attempts. The Advanced Cardiac Life Support (ACLS) guidelines recommend
rewarming to greater than 30°C before attempting further defibrillations if the initial set
are unsuccessful in restoring a perfusing rhythm (Guidelines 2000 for Cardiopulmonary
Resuscitation and Emergency Cardiovascular Care, The American Heart Association).
Clinical judgment, however, may indicate further attempts at defibrillation after
rewarming to temperatures less than 30°C.
CPR with chest compressions should not be initiated on any patient with signs of
life. Chest compressions in the presence of a pulse or QRS complexes on the
electrocardiogram may result in ventricular fibrillation. Initiating CPR and chest
compression for pulseless electrical activity (PEA) should be done only after confirming
that no pulse is present after checking for at least one minute after assisted ventilation and
supplemental oxygen are provided for several minutes.
