What is the approach to diagnosing and treating severe hypothermia (core body temperature of 30 degrees Celsius) of unknown etiology in an asymptomatic patient in a hospital setting?

From the Guidelines

For profound hypothermia (30°C) without known cause in an asymptomatic hospitalized patient, immediate rewarming is essential while investigating the underlying etiology, and core rewarming is often used, although some have reported successful rewarming with active external warming techniques. When managing such a patient, the initial steps should focus on preventing further heat loss and beginning rewarming immediately, as outlined in the 2010 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care 1. The approach should include:

• Preventing additional evaporative heat loss by removing wet garments and insulating the victim from further environmental exposures
• Using external warming techniques, such as forced air or other efficient surface-warming devices, for patients with moderate to severe hypothermia
• Considering core rewarming techniques, including warmed IV or intraosseous (IO) fluids and warm humidified oxygen, as supplementary to active warming techniques
• Not delaying urgent procedures such as airway management and insertion of vascular catheters, despite potential cardiac irritability Key considerations in the management of profound hypothermia include:
• Continuous cardiac monitoring due to the risk of arrhythmias during rewarming
• Targeting a rewarming rate of 0.5-2°C per hour while monitoring core temperature
• Laboratory workup to identify potential causes, including CBC, comprehensive metabolic panel, thyroid function tests, cortisol level, and toxicology screening
• Avoiding rapid rewarming to prevent peripheral vasodilation leading to "rewarming shock" with hypotension
• Reserving active internal rewarming methods for severely symptomatic cases By following these guidelines and considering the patient's asymptomatic status, the primary goal is to safely rewarm the patient while investigating and addressing the underlying cause of hypothermia to prevent recurrence, as recommended by the guidelines 1.

From the Research

Diagnosing Profound Hypothermia

• Profound hypothermia is defined as a core body temperature below 35 °C, with severe hypothermia being below 28 °C 2.
• Diagnosis and assessment of the risk of cardiac arrest are based on clinical signs and core temperature measurement when available 3.
• In a hospital setting, diagnosis can be made using core temperature measurement, and clinical signs such as ventricular dysrhythmias, or systolic blood pressure < 90 mmHg) 3.

Treating Profound Hypothermia

• For hypothermic patients with risk factors for imminent cardiac arrest (temperature < 30 °C in young and healthy patients and <32 °C in elderly persons, or patients with multiple comorbidities), ventricular dysrhythmias, or systolic blood pressure < 90 mmHg), transfer to an extracorporeal life support (ECLS) centre is recommended 3.
• Rewarming can be accomplished by passive and active techniques, with most often, passive and active external techniques being used 3.
• Internal rewarming techniques, such as extracorporeal membrane oxygenation (ECMO), are required only in patients with refractory hypothermia or cardiac arrest 3, 4, 5.
• ECMO rewarming should be performed with veno-arterial extracorporeal membrane oxygenation (ECMO) as it allows a gradual, controlled increase of core body temperature, and provides respiratory and hemodynamic support during the unstable period of rewarming and reperfusion 4, 5.
• In cases of cardiac arrest, continuous cardiopulmonary resuscitation (CPR) should be performed, and mechanical CPR devices should be used for prolonged rescue, if available 3.
• For patients with severe hypothermia and cardiac arrest, ECMO use was associated with faster rewarming and higher hospital survival compared to conventional rewarming methods 2.

Considerations for Asymptomatic Patients

• There is limited information available on the treatment of asymptomatic patients with profound hypothermia without a known cause.
• However, the general principles of rewarming and monitoring for cardiac arrest risk factors can still be applied 3.
• In cases where extracorporeal life support therapy is not available, active external rewarming techniques can be used as an alternative 6.