23-45: Hypothermia

ECG Findings

• Sinus bradycardia or atrial fibrillation with slow ventricular response.

• PR, QRS, and QT intervals are typically prolonged.

• Osborne or “J” wave (a positive deflection of the terminal portion of the QRS complex). The J wave may be subtle or large and “humped.”

Pearls

1. Myocardial damage and ECG changes associated with hypothermia are not necessarily due to low temperature. They may be indirectly caused by systemic circulatory issues such as hypoperfusion.

2. The hypothermic patient’s rhythm slows, proceeding from sinus bradycardia to atrial fibrillation with slow response and may proceed to other arrhythmias including ventricular fibrillation and asystole.

3. The amplitude of the “J” wave corresponds to the degree of hypothermia.

4. Defibrillation and medications may be ineffective in the hypothermic patient. Rapid rewarming is indicated as an initial and critical resuscitative measure.

5. Osborn waves can also be seen in other conditions, including hypercalcemia, brain injury, and subarachnoid hemorrhage.