Hypothermia

Disease name confirmation

• Hypothermia is the medically accurate term. Hypothermia is defined as a core temperature below 35℃ and is classified as mild, moderate, or severe according to clinical severity.

1) Disease description (causes and symptoms)

• Definition and pathophysiology
  • Core temperature < 35℃. A decrease in body temperature occurs due to reduced metabolic heat production (old age, malnutrition, endocrine diseases, etc.), increased heat loss (exposure to low temperatures, immersion, wet clothing, etc.), or impairment of the thermoregulatory center (central nervous system injury, effects of medications or alcohol, etc.).
  • Hypothermia can cause a decreased metabolic rate, electrolyte and acid–base imbalances, increased blood viscosity, impaired coagulation, and changes in myocardial conduction (bradycardia and arrhythmias).
• Main causes
  • Environmental exposure (cold outdoors, immersion in cold water), wet clothing, older adults and infants (vulnerable temperature regulation), medications such as alcohol, sedatives, and opioids, endocrine diseases (hypothyroidism, adrenal insufficiency), trauma or shock, hypoglycemia, etc.
• Symptoms (general progression)
  • Mild (32–35℃): shivering (chills), tachycardia, hyperventilation, slightly elevated blood pressure, fatigue and reduced concentration, impaired judgment, and ataxia.
  • Moderate (28–32℃): loss of shivering, muscle rigidity, possible bradycardia and arrhythmias, stupor, memory impairment, and altered consciousness.
  • Severe (<28℃): loss of reflexes, respiratory failure, hypotension, coma, and risk of ventricular fibrillation and cardiac arrest. Death may occur if the low body temperature persists.

2) Treatment methods

• Emergency principles
  • Prioritize ABCs (airway, breathing, and circulation), prevent further heat loss (remove wet clothing and provide warmth), and minimize movement (to prevent increased cardiac instability).
  • Continuous core temperature monitoring (rectal, esophageal, or bladder sensor).
• Conservative and noninvasive treatment
  • Warmed oxygen and warm drinks and high-calorie food (when consciousness is clear).
  • Administration of warm intravenous fluids (e.g., warmed to 38–42℃).
  • External warming: warming blankets and forced-air warming.
  • Caution: Be aware of the risk of “afterdrop,” in which rapid dilation of peripheral blood vessels causes the core temperature to fall further.
• Active medical rewarming (moderate to severe cases and unstable patients)
  • Warmed intravenous fluids, warmed inhaled gases, warmed peritoneal lavage, gastric lavage and bladder irrigation with warm fluids, etc.
  • In severe patients with cardiac arrest or life-threatening arrhythmias, blood rewarming using extracorporeal membrane oxygenation (ECMO) or extracorporeal circulation (cardiopulmonary bypass) is the most effective method.
• Cardiopulmonary resuscitation and cardiac management
  • Perform standard CPR for cardiac arrest in a hypothermic patient. Because responses to medications and defibrillation are reduced during hypothermia, extend medication intervals or limit defibrillation attempts according to guidelines (follow current guidelines).
  • If an arrhythmia occurs, avoid excessive manipulation and prioritize rewarming.
• Treatment of underlying causes
  • Administer glucose for hypoglycemia; consider hormone replacement if hypothyroidism or adrenal insufficiency is suspected; treat infection and trauma.
• Complications and precautions (including patient self-care)
  • Before reaching the hospital: Remove wet clothing and dry and warm the person (blankets or a heater); if conscious, give warm, nonalcoholic drinks. If consciousness is impaired, secure the airway and arrange immediate emergency transport.
  • In the hospital: Avoid excessive patient movement (which may induce cardiac arrhythmias); refrain from unnecessary repeated defibrillation or medication administration until the core temperature has been restored.
  • Complications: Ventricular fibrillation and cardiac arrest, shock, pulmonary edema and pulmonary hemorrhage, rhabdomyolysis and renal failure, coagulopathy, and infection.

3) Outpatient visit checkpoints (preparations, information, and example questions)

• Preparations (what to bring)
  • List of medications currently being taken (including doses and administration times)
  • Underlying diseases (thyroid, adrenal, liver, kidney, or heart disease, etc.) and previous test results (if available)
  • Time of symptom onset (when exposure occurred), type of exposure (water, outside temperature, whether clothing was wet), and recent alcohol or medication use
  • Record of current symptoms (whether shivering is present, level of consciousness, changes in breathing or heart rate)
  • Whether trauma or bleeding is present
• Information to check before visiting the hospital (example questions)
  • How long were you exposed to the cold recently?
  • Are you conscious, and are you shivering or experiencing chills?
  • What medications have you recently taken (such as sleeping pills, sedatives, or beta-blockers), and have you consumed alcohol?
  • Do you have a history of hypothyroidism, adrenal insufficiency, or hypoglycemia?

4) Examples of general questions to ask the doctor

• Do I need to be hospitalized based on my condition and severity? How long is hospitalization expected to last?
• What are the most important risks during the current treatment (such as arrhythmia or cardiac arrest), and how will they be monitored?
• What is the risk of complications during or after treatment (such as kidney or heart problems)?
• What are the advantages and disadvantages of the rewarming methods (external versus internal rewarming), and what are the criteria for procedures that may be needed (such as ECMO)?
• What precautions should I take when returning to daily activities, work, or driving after discharge?

5) Examples of disease-specific questions

• At what core temperature (or measured body temperature) would you recommend emergency treatment (such as visiting the emergency department, hospitalization, or ECMO)?
• If an abnormal heart rhythm occurs, what treatment will I receive first (defibrillation, medication, extracorporeal rewarming, etc.)?

Brief summary

• A core temperature below 35℃ indicates hypothermia, which can have various causes, including environmental exposure, medications, endocrine diseases, older age, and infancy. Initial treatment consists of preventing heat loss, providing warmth, oxygen, and warm intravenous fluids; severe or unstable patients require active internal warming (such as peritoneal lavage or ECMO). Because this is an emergency, immediately transport the person to a medical institution if hypothermia is suspected.