Hypothermia

Figure 65.1. ECG of a patient with hypothermia and Osborn waves.

Diagnosis and evaluation

Confirm hypothermia with rectal thermometer, indwelling Foley with temperature sensor, or other means of core temperature measurement.
In general, hypothermia is a clinical diagnosis. However, laboratory tests may be helpful to look for an underlying condition that caused a patient to become hypothermic. For example, it may be the patient had a stroke or myocardial infarction and fell into a snow bank.
- Laboratory studies: complete blood count (CBC), metabolic panel, coagulation profile
- ECG
- Chest radiograph
- Depending on the clinical situation: cardiac enzymes, serial blood gases, cultures, computed tomography (CT) of the head, additional imaging.

Critical management

Initial management should focus on resuscitation, rewarming, and fluid expansion
- Basic steps:
  - Secure the airway.
  - Remove wet clothing.
  - Intravenous (IV) access.
  - Cardiac monitoring, temperature monitoring.
- Rewarming:
  - Passive external rewarming.
  - Active internal rewarming is indicated only in severe cases:
    - Cardiovascular instability.
    - Temperature below 32.2°C.
    - Can use gastrointestinal, bladder, peritoneal, pleural, and/or mediastinal lavage in severe cases.
- Fluids:
  - Start with 500mL of D5 in 0.9% normal saline fluid challenge until laboratory results are available
Watch for signs of core temperature afterdrop:
- Thought to occur when cold blood from the extremities returns to central circulation as peripheral vessels dilate during the rewarming process.
Correct any unstable cardiac rhythms:
- Usually atrial fibrillation and atrial flutter will resolve upon rewarming.
- Ventricular fibrillation can occur and is usually refractory until the patient is warmed, but one defibrillation attempt is recommended.
Vasopressor support should be initiated as needed for hypotension.
Other treatments: Cardiopulmonary bypass has been used in some cases of severe hypothermia to rewarm patients and provide circulatory support.
Disposition: All patients with moderate to severe symptomatic hypothermia should be admitted to the hospital for rewarming and observation. Patients with mild hypothermia who are otherwise healthy can be rewarmed in the emergency department.

Sudden deterioration

Hypothermic patients that are deteriorating will need to have their airway managed. There is no contraindication to performing rapid sequence induction (RSI) with the usual drug regimen in these patients.

Patients who develop pulseless arrhythmias secondary to shockable rhythms should be managed according to advanced cardiac life support guidelines. While CPR should be initiated promptly, drug boluses should be avoided unless the patient is in asystole, and defibrillation should be attempted only once until the patient has been rewarmed to more than 30°C.

Vasopressor of choice: norepinephrine.