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Emergency And Acute Medicine – Hypothermia
Basics
Description Core body temperature <35°c. risk factors include impaired thermoregulation (infants, elderly), comorbid illness, intoxication, and environmental exposure. heat loss occurs via radiation (most significant), conduction, convection, evaporation, respiration. production relies on shivering, nonshivering thermogenesis, increased thyroxine epinephrine.< />pan>
Etiology
Dermal disease (burns, exfoliative dermatitis, severe psoriasis). Drug induced (ethanol, phenothiazines, sedative–hypnotics). Environmental exposure (immersion, nonimmersion). Iatrogenic causes (aggressive fluid resuscitation, heat stroke treatment). Metabolic disorders (hypothyroidism, hypopituitarism, hypoadrenalism). Neurologic conditions (spinal cord injury, head trauma, stroke, tumor, Wernicke disease). Neuromuscular inefficiency (extremes of age, impaired shivering, lack of acclimatization). Sepsis. Pediatric patients are at higher risk because of increased surface area to mass ratio; consider nonaccidental trauma.
Diagnosis
Signs And Symptoms
Mild (35–32.2°C): Hypertension, shivering, tachycardia progressing to bradycardia, tachypnea, vasoconstriction, apathy, ataxia, cold diuresis, impaired judgment.
Moderate (32.2–28°C): Atrial dysrhythmias, bradycardia refractory to atropine, decreased level of consciousness, hypoventilation with CO₂ retention, dilated pupils, diminished gag reflex, cessation of shivering, hyporeflexia, hypotension, J (Osborn) waves.
Severe (<28°c): apnea, coma, minimal eeg activity, nonreactive pupils, oliguria, pulmonary edema, ventricular dysrhythmias or asystole.< />pan>
History Duration and circumstances of cold exposure or submersion.
Physical Exam Pulse and blood pressure may be difficult to detect; pupils often dilated at very low temperatures.
Essential Workup Accurate core temperature measurement.
Diagnosis Tests And Interpretation
Lab Fingerstick glucose, ABG (no temperature correction), CBC (hemoconcentration), electrolytes, BUN/creatinine, potassium, CPK, lactate, coagulation studies, toxicology screen.
Imaging CXR for pneumonia.
ECG Bradyarrhythmias, atrial fibrillation, ventricular fibrillation, prolonged PR/QRS/QT, Osborn waves.
Differential Diagnosis Environmental exposure, sepsis, CNS pathology, metabolic disorders, drug toxicity.
Treatment
Prehospital Patient is not dead until “warm and dead.” Prolonged pulse checks (30–45 s). CPR during transport if indicated.
Initial Stabilization/Therapy ABCs, supplemental oxygen, safe intubation if needed, cardiac monitoring, warmed IV fluids (D5NS preferred), remove wet clothing, passive rewarming, naloxone, dextrose, and thiamine for altered mental status, stress-dose steroids if adrenal insufficiency suspected.
Emergency Department Treatment/Procedures Handle gently to avoid precipitating ventricular fibrillation. Most dysrhythmias resolve with rewarming alone. Defibrillate up to 1–3 times below 28–30°C, then defer until rewarmed. Active rewarming is required for core temperature <32°c. use passive external rewarming for mild cases, active (forced warm air, trunk first) moderate and core (humidified oxygen, warmed iv fluids, peritoneal or pleural lavage, extracorporeal including hemodialysis cardiopulmonary bypass) severe hypothermia cardiac arrest. faster rates (1–2°c />r) are associated with better outcomes.
Medication Amiodarone for persistent ventricular dysrhythmias after rewarming, dextrose for hypoglycemia, hydrocortisone or methylprednisolone if adrenal insufficiency suspected, levothyroxine only for myxedema coma, naloxone, thiamine.
Follow-Up And Disposition
Admission Criteria Moderate to severe hypothermia (<32°c).< />pan>
Discharge Criteria Young, healthy patients with very mild hypothermia who normalize and have a safe, warm environment.
Follow-Up Recommendations Social services involvement for patients at risk of recurrent cold exposure.
Key Points And Cautions Defibrillation is rarely effective below 28–30°C. Atrial fibrillation often resolves with rewarming alone. Beware afterdrop and rewarming shock. Gentle handling and adequate volume resuscitation are essential.
Basics
Description Core body temperature <35°c. risk factors include impaired thermoregulation (infants, elderly), comorbid illness, intoxication, and environmental exposure. heat loss occurs via radiation (most significant), conduction, convection, evaporation, respiration. production relies on shivering, nonshivering thermogenesis, increased thyroxine epinephrine.< />pan>
Etiology
Dermal disease (burns, exfoliative dermatitis, severe psoriasis). Drug induced (ethanol, phenothiazines, sedative–hypnotics). Environmental exposure (immersion, nonimmersion). Iatrogenic causes (aggressive fluid resuscitation, heat stroke treatment). Metabolic disorders (hypothyroidism, hypopituitarism, hypoadrenalism). Neurologic conditions (spinal cord injury, head trauma, stroke, tumor, Wernicke disease). Neuromuscular inefficiency (extremes of age, impaired shivering, lack of acclimatization). Sepsis. Pediatric patients are at higher risk because of increased surface area to mass ratio; consider nonaccidental trauma.
Diagnosis
Signs And Symptoms
Mild (35–32.2°C): Hypertension, shivering, tachycardia progressing to bradycardia, tachypnea, vasoconstriction, apathy, ataxia, cold diuresis, impaired judgment.
Moderate (32.2–28°C): Atrial dysrhythmias, bradycardia refractory to atropine, decreased level of consciousness, hypoventilation with CO₂ retention, dilated pupils, diminished gag reflex, cessation of shivering, hyporeflexia, hypotension, J (Osborn) waves.
Severe (<28°c): apnea, coma, minimal eeg activity, nonreactive pupils, oliguria, pulmonary edema, ventricular dysrhythmias or asystole.< />pan>
History Duration and circumstances of cold exposure or submersion.
Physical Exam Pulse and blood pressure may be difficult to detect; pupils often dilated at very low temperatures.
Essential Workup Accurate core temperature measurement.
Diagnosis Tests And Interpretation
Lab Fingerstick glucose, ABG (no temperature correction), CBC (hemoconcentration), electrolytes, BUN/creatinine, potassium, CPK, lactate, coagulation studies, toxicology screen.
Imaging CXR for pneumonia.
ECG Bradyarrhythmias, atrial fibrillation, ventricular fibrillation, prolonged PR/QRS/QT, Osborn waves.
Differential Diagnosis Environmental exposure, sepsis, CNS pathology, metabolic disorders, drug toxicity.
Treatment
Prehospital Patient is not dead until “warm and dead.” Prolonged pulse checks (30–45 s). CPR during transport if indicated.
Initial Stabilization/Therapy ABCs, supplemental oxygen, safe intubation if needed, cardiac monitoring, warmed IV fluids (D5NS preferred), remove wet clothing, passive rewarming, naloxone, dextrose, and thiamine for altered mental status, stress-dose steroids if adrenal insufficiency suspected.
Emergency Department Treatment/Procedures Handle gently to avoid precipitating ventricular fibrillation. Most dysrhythmias resolve with rewarming alone. Defibrillate up to 1–3 times below 28–30°C, then defer until rewarmed. Active rewarming is required for core temperature <32°c. use passive external rewarming for mild cases, active (forced warm air, trunk first) moderate and core (humidified oxygen, warmed iv fluids, peritoneal or pleural lavage, extracorporeal including hemodialysis cardiopulmonary bypass) severe hypothermia cardiac arrest. faster rates (1–2°c />r) are associated with better outcomes.
Medication Amiodarone for persistent ventricular dysrhythmias after rewarming, dextrose for hypoglycemia, hydrocortisone or methylprednisolone if adrenal insufficiency suspected, levothyroxine only for myxedema coma, naloxone, thiamine.
Follow-Up And Disposition
Admission Criteria Moderate to severe hypothermia (<32°c).< />pan>
Discharge Criteria Young, healthy patients with very mild hypothermia who normalize and have a safe, warm environment.
Follow-Up Recommendations Social services involvement for patients at risk of recurrent cold exposure.
Key Points And Cautions Defibrillation is rarely effective below 28–30°C. Atrial fibrillation often resolves with rewarming alone. Beware afterdrop and rewarming shock. Gentle handling and adequate volume resuscitation are essential.
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