Answer
C. Hypothermia
This patient was diagnosed with hypothermia. His ECG demonstrated
classic abnormalities of hypothermia (most notably, profound sinus
bradycardia); additionally, all leads showed the classic Osborne waves
(J waves) at the junction of the QRS complex and the ST segment (see
Figure 2) representing alterations in ventricular repolarization.
Classically, Osborne waves do not affect the ST segment; however, an ECG
must be interpreted within the clinical context.
This case is an example of primary hypothermia. This occurs when an
unprepared individual faces unanticipated environmental exposure.
Primary hypothermia must be distinguished from secondary hypothermia, in
which a medical illness causes the body's temperature set-point to be
reduced.
Mild hypothermia is a core body temperature of 90–95°F (32.2–35.0°C);
patients may initially show signs of shivering, tachycardia,
vasoconstriction and tachypnea. Later signs include apathy, ataxia,
impaired judgment and diuresis. Moderate hypothermia is a temperature of
82.4–89.9°F (28.0–32.2°C), with signs of dysrhythmia, bradycardia,
hypotension, Osborne waves on ECG, diminished reflexes, dilated pupils
and decreased consciousness. Severe hypothermia is a core body
temperature of 82.4°F (28°C), at which point apnea, decreased
electroencephalographic activity, nonreactive pupils, oliguria,
pulmonary edema, coagulopathy, hemoconcentration and more severe
arrhythmia are seen. Mild or moderate hypothermic patients have an
excellent chance of recovery, but patients with severe hypothermia have a
mortality rate of roughly 50 percent.
Initial stabilization begins with an accurate, continuous means of
measuring the core body temperature to detect the degree of hypothermia
and the response to therapy. Patients may need a rectal, esophageal or
bladder thermometer for continuous measurements. Wet clothing should be
removed immediately. Patients in respiratory failure should be
intubated, mechanically ventilated, and given warmed, humidified,
supplemental oxygen. Volume resuscitation should be initiated with
warmed (104–113°F, or 40–45°C) normal saline. Cardiac reserve is
decreased in hypothermic patients and, therefore, judicious volume
resuscitation is advised. Cardiac arrhythmia can occur, the management
of which may differ in hypothermic patients. Rewarming the patient is
typically sufficient to regain normal myocardial contractility and
rhythm.
There are three general types of rewarming techniques: passive external,
active external and active internal. Passive external rewarming is for
mildly hypothermic patients and involves insulating the patient to allow
the intact thermoregulatory mechanisms to reheat the body. Having
patients inspire humidified air allows for slow but steady increases in
the core body temperature. Active external rewarming includes warm-water
immersion, forced-air warming systems or placement in a heat cradle; a
major complication is core temperature after drop, in which cold
peripheral blood rapidly returns to the heart leading to inappropriate
temperature readings and subsequent inappropriate management. Active
internal rewarming is reserved for severe hypothermia or for patients
who do not respond to less aggressive measures. It can be either
minimally invasive (e.g., heated, humidified air and warm intravenous
fluids) or more invasive (e.g., body cavity lavage, hemodialysis,
cardiopulmonary bypass and extracorporeal blood warming). The least
invasive means of adequate rewarming is generally best.
This patient had moderate hypothermia and was immediately stripped of
his clothes. He was given warm intravenous fluids and a mask with warm,
humidified air to breathe. A forced-air blanket was used on his torso,
and warmed blankets were wrapped around his extremities. With these
measures, the patient's core body temperature began to rise and his
symptoms resolved. He was admitted for monitoring and treatment of his
pneumonia. Eventually, the patient was discharged without any major
disabilities.