Cold Injuries

1. THE 2-MINUTE PHYSIOLOGY (Rapid Pathophysiology)

• Systemic Hypothermia: Core body temperature drops below 35°C. The physiological breakdown is bipartite. First, hypothermia directly induces coagulation dysfunction and decreases platelet aggregation, which critically complicates hemorrhage control in trauma patients. Second, as the core temperature drops (especially <28°C), myocardial conduction is impaired, significantly lowering the fibrillation threshold and leading to ventricular dysrhythmias and cardiac arrest.
• Frostbite: Occurs when soft tissue completely freezes. The direct mechanical destruction is multifactorial: cold-related ischemia (from profound vasoconstriction and vascular thrombosis) combined with the physical formation of extracellular and intracellular ice crystals. This damage is further compounded by severe reperfusion inflammatory changes upon rewarming. It preferentially affects the fingers, toes, ears, nose, chin, and cheeks.

2. THE BEDSIDE ACTION PLAN (Rapid ER Management)

• The 60-Second Rule: Severely hypothermic patients may have profound, life-sustaining bradycardia that is difficult to palpate. If there are no obvious vital signs, you must perform a full 60-second breathing and pulse check (or assess with a cardiac monitor) before initiating CPR to avoid precipitating ventricular fibrillation.
• Handling the Patient: Employ minimal, cautious movements to avoid triggering lethal ventricular arrhythmias. If the patient is pregnant, ensure left uterine displacement (LUD) is performed.
• Systemic Rewarming: Initiate active external and minimally invasive rewarming strategies (insulation, hot packs, forced air blankets, warmed IV fluids). Focus active heat application directly to the upper trunk.
• Frostbite Management:
• Rewarm the affected extremity rapidly via warm water immersion.
• Remove all constrictive clothing.
• Administer parenteral narcotics for pain management alongside Ibuprofen (600 mg or 10 mg/kg/dose every 6 hours).
• Apply topical aloe vera cream every 6 hours and update tetanus immunization.

3. THE DIAGNOSTIC GRID (Differential Diagnosis & Workup)

• Critical Workup for Severe Cold Injury / Frostbite:
• Metabolic & Renal: Basic Metabolic Panel (BMP), lactate, blood gas, Creatine Kinase (CK), and urine myoglobin (to assess for cold-induced rhabdomyolysis).
• Hematology: Complete Blood Count (CBC) to screen for anemia and thrombocytopenia, PT/PTT, and INR (evaluating for cold-induced coagulopathy).
• Cardiovascular: Troponin, ECG, echocardiogram, and D-dimer.
• Hepatic: Liver function tests (transaminases, bilirubin).
• The Lethal Potassium Cutoff: In cases of hypothermic cardiac arrest, obtaining a serum potassium is critical. A serum potassium level > 12 mmol/L is a marker of irreversible cellular death and indicates futility for Extracorporeal Membrane Oxygenation (ECMO).

4. THE VISUAL BOARD (ECG / POCUS / Imaging)

• The Frostbite Visual Exam: Inspect the frozen extremities or ears. The presence of hemorrhagic blisters definitively classifies the injury as second-degree frostbite.
• Imaging: Obtain a Head CT to evaluate for cerebral edema in patients presenting with severe systemic hypothermia and altered mental status.
• ECG Monitoring: Actively look for ventricular dysrhythmias, which are highly likely once the core temperature falls below 28°C.

5. THE SCORING MATRIX (Risk Stratification & Guidelines)

Emergency disposition and resuscitation efforts in severe accidental hypothermia hinge on specific criteria:

• Transfer Criteria: Patients require transport to a specialty center if they exhibit prehospital cardiac instability (SBP < 90 mm Hg or ventricular dysrhythmias), impaired consciousness, or a core temperature < 28°C. Frostbite patients should be transferred to a frostbite-capable facility if advanced treatments can be implemented within 24 hours of rewarming.
• ECMO/CPB Indications: Consider Extracorporeal Membrane Oxygenation (ECMO) or Cardiopulmonary Bypass (CPB) in hypothermic cardiac arrest if: Core temperature is < 32°C AND Serum potassium is < 12 mmol/L.
• Avalanche Resuscitation Termination: Terminate CPR if an avalanche burial exceeded 35 minutes AND the airway is packed with snow.

6. THE DANGER ZONE (Pitfalls & Critical Actions)

• Pitfall: Vigorously massaging frostbitten or cold extremities during transport or in the ED. This causes catastrophic mechanical tissue destruction from ice crystals.
• Pitfall: Acutely debriding frostbite blisters or soft tissue in the ED. Guidelines explicitly state: "No blister or soft tissue debridement acutely".
• Pitfall: Failing to prevent iatrogenic hypothermia during the ATLS "E" (Exposure) phase. Hypothermia significantly increases trauma mortality; patients must be completely covered immediately after the exam.
• Critical Action: Prevent refreezing at all costs. Never initiate rewarming of a frostbitten limb if there is a risk it will refreeze during transport.

7. MCQ MASTERCLASS (Written Exam Tips)

• Buzzword: "Hemorrhagic blisters" on the ears of a skier. Answer: Second-degree frostbite.
• Buzzword: "Airway packed with snow" and "burial > 35 minutes" in an avalanche victim. Answer: Withhold/Terminate CPR (irreversible death).
• Distractor Option: In a question regarding initial frostbite management, an option will suggest "Build a fire to immediately start rewarming." Correction: This is incorrect; the standard of care is immersing the lower extremities in warm water.
• Distractor Option: You will be prompted to debride a hemorrhagic blister. Correction: Never debride blisters acutely; apply topical aloe vera and meticulous local care.
• High-Yield Fact: Be aware that intra-arterial thrombolysis is an advanced therapy for extremity frostbite that has been shown to decrease digital amputation rates if initiated promptly.

8. THE BOARDROOM SCRIPT (OSCE & Oral Board Tips)

• The Trauma/Exposure Pearl: "I will expose the patient to identify all external signs of injury, but to respect the patient's dignity and prevent lethal hypothermia-induced coagulopathy, I will cover the patient with warm blankets immediately after the examination."
• The Bradycardia Pulse Check: "Because this patient is severely hypothermic and at high risk for ventricular fibrillation if jostled, I will instruct the team to use minimal, cautious movements. Before initiating chest compressions, I will assess for breathing and central pulses for a full 60 seconds."
• The Frostbite Transfer: "I will begin rewarming the frostbitten extremity via warm water immersion, administer parenteral narcotics and ibuprofen, and apply topical aloe. Because we are within the 24-hour window, I will consult vascular surgery or arrange transfer for possible intra-arterial thrombolysis to salvage the digits."