From the Guidelines
Hypothermia is a medical condition characterized by a body temperature below 35°C, which can lead to altered mental status, shivering, and eventually, life-threatening complications. According to the 2024 American Heart Association and American Red Cross guidelines for first aid 1, hypothermia can be classified into different levels, including cold stress (35-37°C), mild hypothermia (32-35°C), moderate hypothermia (28-32°C), severe hypothermia (<28°C), and profound hypothermia (<24°C). Each level has distinct signs and symptoms, ranging from shivering and altered mental status to unresponsiveness and cardiac arrest.
Signs and Symptoms of Hypothermia
- Cold stress: alert, possibly shivering
- Mild hypothermia: altered level of responsiveness, shivering
- Moderate hypothermia: decreased level of responsiveness, possible shivering
- Severe hypothermia: unresponsive, may appear lifeless
- Profound hypothermia: cessation of shivering, slow heart rate and breathing
Treatment and Prevention of Hypothermia
Treatment of hypothermia involves gentle rewarming by moving to a warm environment, removing wet clothing, using warm blankets, and providing warm beverages if the person is conscious. Severe hypothermia requires immediate medical attention with professional rewarming techniques. Prevention involves dressing in layers, staying dry, limiting time outdoors in extreme cold, and being prepared with proper clothing and emergency supplies when in potentially cold environments. Additionally, removing wet clothing, avoiding further heat loss, and increasing ambient temperature can help reduce the risk of hypothermia and hypothermia-induced coagulopathy 1.
High-Risk Groups and Complications
Certain groups, such as the elderly, very young children, people with specific medical conditions, and those under the influence of alcohol or drugs, are at higher risk of developing hypothermia. Hypothermia can also lead to coagulopathy, increased morbidity and mortality, and higher blood loss and transfusion requirements, especially in trauma patients 1. Therefore, it is essential to target normothermia with core temperatures between 36 and 37°C to create optimal pre-conditions for coagulation.
From the Research
Definition of Hypothermia
- Hypothermia is defined as an unintentional drop of the body core temperature below 35 °C 2
- It can lead to cardiocirculatory instability and reversible cardiac arrest 2
- Severe hypothermia is considered a life-threatening condition, with a core body temperature below 28°C 3
Classification of Hypothermia
- The Swiss Staging System classifies hypothermia into different stages, including class III (hypothermic cardiac instability) and class IV (hypothermic cardiac arrest) 4
- The severity of hypothermia is determined by both temperature and clinical presentation, which can be difficult to assess in a prehospital setting 4
Treatment of Hypothermia
- Extracorporeal membrane oxygenation (ECMO) is a recommended treatment for severe hypothermia, particularly in cases of cardiac arrest 5, 4, 2, 3, 6
- ECMO can provide rapid and efficient rewarming, as well as respiratory and hemodynamic support during the unstable period of rewarming and reperfusion 4
- Veno-arterial ECMO is a preferred technique due to its lower anticoagulation requirements and potential to prolong circulatory support 2
- Veno-venous ECMO may also be considered as a first-line strategy for rewarming in accidental hypothermia complicated by cardiac arrest 6