Emergency Medicine · Year 3 · from Emergency Medicine

Case 2: Severe Hypothermia - The Found Down Patient

Patient Demographics

• Age: 58 years
• Sex: Male
• Occupation: Unemployed

Chief Complaint

"Found unresponsive in the park."

History of Present Illness

A 58-year-old homeless male is found unresponsive on a park bench by police during a cold snap (ambient temperature -8C/18F). He was last seen by shelter workers 18 hours ago. On EMS arrival, patient is unresponsive with very slow respirations and barely palpable pulse. EMS initiated gentle handling and passive rewarming en route.

Initial Assessment

ESI Level: 1 - Critical hypothermia

First Impression:

• Appearance: Unresponsive, appears lifeless
• Work of breathing: Very slow, shallow
• Circulation: Cyanotic, cold to touch

Vital Signs (obtained carefully):

• Heart rate: 32 bpm (difficult to palpate)
• Blood pressure: 78/palp
• Respiratory rate: 6 breaths/min
• SpO2: Unable to read (vasoconstriction)
• Core Temperature (esophageal): 26.4C (79.5F) - SEVERE HYPOTHERMIA
• GCS: 3

Hypothermia Classification

This patient: SEVERE hypothermia (26.4C)

Primary Survey - Modified for Hypothermia

Airway:

• Patent
• Endotracheal intubation performed (warmed, humidified oxygen)

Breathing:

• Very slow (6/min) - assisted ventilation
• Lungs clear
• Bag-valve-mask with warmed, humidified oxygen

Circulation:

• Severe bradycardia (32 bpm)
• Hypotensive
• Difficult IV access (vasoconstriction)
• Check pulse for 60 seconds (may be very slow/weak)
• ECG obtained

Disability:

• GCS 3 (comatose)
• Pupils fixed, dilated (BUT may recover with rewarming)

Exposure:

• Remove wet clothing
• Dry thoroughly
• Cover with warming blankets
• Handle GENTLY (avoid rough movement - arrhythmia risk)

ECG Findings

Classic ECG Changes in Hypothermia:

• Bradycardia (HR 32)
• Osborn (J) waves present (positive deflection at J point)
• Prolonged intervals (PR, QRS, QT)
• Atrial fibrillation at presentation (common)

Rewarming Strategy

Severity determines approach:

This patient - ACTIVE INTERNAL REWARMING indicated:

1. Warm IV fluids (38-42C)
2. Warm humidified oxygen
3. Body cavity lavage (bladder, gastric, thoracic)
4. ECMO/cardiopulmonary bypass - if available and cardiac arrest

Initial Rewarming Initiated:

• Warm IV crystalloid via rapid infuser
• Bair Hugger warming blanket
• Bladder lavage with warm saline
• Heated, humidified ventilation

Management Considerations

CPR in Hypothermia:

• If no pulse after 60 seconds of checking, start CPR
• Continue CPR until rewarmed to >30-32C or spontaneous circulation
• "Not dead until warm and dead"
• Defibrillation: May attempt once, but usually ineffective until temp >30C
• ACLS medications: Withhold until temp >30C (reduced metabolism)

This patient:

• Had detectable pulse (32 bpm) - no CPR indicated
• Focus on rewarming and supportive care

Secondary Survey

SAMPLE History (limited):

• Symptoms: Found unresponsive
• Allergies: Unknown
• Medications: Unknown
• PMH: Per shelter records - alcohol use disorder, no other known medical history
• Last Meal: Unknown
• Events: Cold exposure overnight

Physical Examination:

• General: Cold, cyanotic, appears lifeless
• Skin: No frostbite visible, no trauma
• Abdomen: Distended (diminished motility)
• Neuro: Comatose, areflexic

Diagnostic Testing

Labs:

• ABG: pH 7.08, pCO2 32, HCO3 10 (severe metabolic acidosis)
• K: 5.2 (increases with hypothermia)
• Glucose: 42 (hypoglycemia common) - D50 given
• Lactate: 9.2 mmol/L
• Ethanol level: 0.18% (intoxication, contributed to exposure)
• Ammonia: Mildly elevated
• CBC: Hematocrit 52% (hemoconcentration)
• Coagulation: PT 22, prolonged (coagulopathy)

Toxicology: Consider carbon monoxide if enclosed space

Clinical Course

Rewarming Progress:

• Hour 1: Temp 27.8C, HR 38
• Hour 2: Temp 29.4C, HR 48, BP 92/60
• Hour 4: Temp 32.0C, HR 68, BP 108/72, spontaneous movements
• Hour 8: Temp 35.2C, extubated, following commands

Complications During Rewarming:

• "Afterdrop" phenomenon: Core temp initially dropped slightly as cold peripheral blood returned to core
• Hypotension: Required fluid resuscitation
• Arrhythmias: Brief runs of VT during rewarming (treated expectantly)

Disposition

• ICU admission for continued monitoring
• Full neurological recovery by day 2
• Social work consultation
• Shelter placement arranged
• Alcohol cessation resources provided
• Discharged day 4

Teaching Points

1. "Not dead until warm and dead": Neurological recovery possible even after prolonged hypothermia with apparent death
2. Check pulse for 60 seconds: Pulses may be very slow and weak
3. Gentle handling: Rough movement can trigger ventricular fibrillation in cold heart
4. J waves (Osborn waves): Pathognomonic ECG finding of hypothermia
5. Defibrillation timing: Usually ineffective until temperature >30C; one attempt reasonable
6. Core temperature measurement: Rectal, esophageal, or bladder; peripheral unreliable
7. Rewarming method matches severity: Severe hypothermia needs active internal rewarming
8. Look for underlying cause: Sepsis, hypoglycemia, intoxication, trauma often coexist

Clinical Image

Image Description: 12-lead ECG demonstrating classic features of hypothermia including bradycardia and Osborn (J) waves - the characteristic positive deflection at the J point seen best in leads II, V5, and V6 (arrows).

Attribution: Image from Wikimedia Commons, Osborn wave ECG. Licensed under CC BY-SA 3.0. Source: https://commons.wikimedia.org/wiki/File:Osborn_waves.jpg

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