Stages of Hypothermia
|Early Stage||Decompensated Stage|
|Shivering||Cold diuresis-kidneys unable to concentrate urine|
|J wave on ECG|
|Diminished gag reflex|
|Loss of shivering|
|No activity on EEG|
- Many thermometers do not measure below 34.4°C (94°F). Need special low-tempsensing rectal or bladder thermometers.
- Avoid jostling the hypothermic patient too much because of myocardial irritability and consequent arrhythmias.
Direct complications from hypothermia and rewarming
- Acute tubular necrosis and renal failure
- Electrolyte shifts, especially K+ because of acid-base changes during rewarming
- Hypoglycemia from depleted glycogen stores
- Functional coagulapathy: May have normal coag studies because have to be rewarmed to run the assay
- Passive Rewarming: Remove cold, damp clothes. Wrap with blankets.
Active External Rewarming: Apply heat to skin
- Heating blanket or radiant heat
- Hot water bottles or heating pads to truncal surfaces. Caution-- do not burn skin.
- Risk of “Core Temperature Afterdrop”, vasodilation with active external rewarming causes cold peripheral blood to return to heart. Give warm IV fluid beforehand.
- Risk of “Rewarming Acidosis”. Lactate from periphery returns to core circulation. May cause transient shock during rewarming.
Active Core Rewarming
- Humidified air, 40°C (104°F) – increases core temp by 1-2.5°C (1.8-4.5°F) per hr
- Warm IV fluids at 40-45°C
- Cardiopulmonary bypass or hemodialysis, Increases core temp by 1-2°C (1.8-3.6°F) every 3-5 minutes
- Warm fluid lavage of stomach, colon, bladder, pleural space
- Peritoneal dialysis. Normal saline at 40-45°C at 6-10 L/hr increases core temp by 1-3°C (1.8-5.4°F) per hour when combined with heated oxygen.
- Mediastinal lavage via open thoracotomy
Choosing a rewarming approach
- Check glucose.
- Consider thiamine 100 mg IV, esp if chronic EtOH at risk for Wernicke’s
- Treat underlying etiology for hypothermia
- Give antibiotics +/- steroids, as appropriate
If patient in cardiopulmonary arrest
- Intubate, CPR, ACLS protocol
- Warm IVF
- Heated humidified oxygen
- Extracorporeal rewarming (i.e. cardiopulmonary bypass), if not immediately available, do active core rewarming measures
- Rewarm to target temperature >30°C (86°F)
If NOT in cardiopulmonary arrest AND temperature <32°C (89.6°F)
- Active External Rewarming (i.e. Bair Hugger, warm blankets), and
- Minimally invasive Active Core Rewarming (warm IVF, warm air)
If NOT in cardiopulmonary arrest AND temp ≥32°C (89.6°F)
- Passive external rewarming measures
- McCullough L, Arora S. Diagnosis and treatment of hypothermia. Am Fam Physician. 2004 Dec 15;70(12):2325-32. [PubMed]