Hypothermia And Cold Related Injury
Introduction
Hypothermia and cold-related injuries are significant health concerns in Canada, given its cold climate and outdoor-oriented culture. As a Canadian medical student preparing for the MCCQE1, understanding these conditions is crucial for providing effective care in various healthcare settings across the country.
This article is designed to help you prepare for the MCCQE1 exam by covering key concepts, Canadian guidelines, and providing practice questions on hypothermia and cold-related injuries.
Epidemiology in Canada
- Canada experiences approximately 80 cold-related deaths annually
- Higher incidence in northern territories and prairie provinces
- At-risk populations include:
- Homeless individuals
- Outdoor workers
- Winter sports enthusiasts
- Elderly with limited mobility or cognitive impairment
Pathophysiology
Step 1: Initial Cold Exposure
- Peripheral vasoconstriction
- Increased metabolic rate
Step 2: Prolonged Exposure
- Decreased core body temperature
- Impaired cellular function
Step 3: Severe Hypothermia
- Organ dysfunction
- Cardiac arrhythmias
- Coagulopathy
Types of Cold-Related Injuries
- Core body temperature <35°C
- Classified as mild, moderate, or severe
- Affects multiple organ systems
Clinical Presentation
Hypothermia Stages
| Stage | Core Temperature | Clinical Features |
|---|---|---|
| Mild | 32-35°C | Shivering, tachycardia, tachypnea |
| Moderate | 28-32°C | Altered mental status, bradycardia, hypotension |
| Severe | <28°C | Coma, severe bradycardia, risk of ventricular fibrillation |
Frostbite Stages
- First-degree: Erythema, edema
- Second-degree: Superficial skin blistering
- Third-degree: Full-thickness skin freezing
- Fourth-degree: Tissue freezing extending to muscle and bone
Diagnosis
- Clinical assessment
- Core body temperature measurement
- ECG monitoring for arrhythmias
- Laboratory tests:
- CBC
- Electrolytes
- Coagulation profile
- Arterial blood gases
For the MCCQE1, focus on recognizing the clinical signs and symptoms of hypothermia and cold-related injuries, as well as appropriate diagnostic approaches in the Canadian healthcare context.
Management
Step 1: Prehospital Care
- Remove wet clothing
- Passive external rewarming for mild hypothermia
- Active external rewarming for moderate to severe cases
Step 2: Hospital Management
- Airway management and ventilation support if needed
- Fluid resuscitation with warmed IV fluids
- Active core rewarming techniques:
- Warm air inhalation
- Peritoneal lavage
- Extracorporeal blood rewarming (in severe cases)
Step 3: Frostbite Management
- Rapid rewarming in 37-39°C water
- Pain management
- Tetanus prophylaxis
- Consider thrombolysis in severe cases (as per Canadian guidelines)
Step 4: Complications Management
- Treat arrhythmias
- Correct electrolyte imbalances
- Monitor for and manage rhabdomyolysis
Canadian Guidelines for Hypothermia Management
The Canadian Medical Association Journal (CMAJ) provides specific guidelines for managing accidental hypothermia in Canadian healthcare settings:
- Use Swiss staging system for initial triage
- Employ active external and minimally invasive rewarming for stages I-II
- Consider extracorporeal life support (ECLS) for stages III-IV
- Follow a structured approach to resuscitation and rewarming
MCCQE1 Tip
Remember that Canadian guidelines emphasize the importance of early recognition and aggressive management of hypothermia, given the country's climate and outdoor activities.
Prevention Strategies in Canada
- Public education on cold weather safety
- Proper clothing and equipment for outdoor activities
- Community-based programs for vulnerable populations
- Workplace safety regulations for outdoor workers
Key Points to Remember for MCCQE1
- Understand the stages of hypothermia and their clinical presentations
- Know the Canadian-specific epidemiology and risk factors
- Be familiar with the diagnostic approach, including core temperature measurement
- Understand the principles of rewarming techniques
- Know the Canadian guidelines for hypothermia management
- Be aware of potential complications and their management
- Understand the importance of prevention strategies in the Canadian context
Sample Question
Question
A 28-year-old man is brought to the emergency department after being found unconscious in a snow bank. His core body temperature is 26°C, and he has a weak pulse of 30 beats per minute. Which one of the following is the most appropriate next step in management?
- A. Administer warm IV fluids and apply heating blankets
- B. Begin chest compressions immediately
- C. Perform peritoneal lavage with warm fluids
- D. Start extracorporeal membrane oxygenation (ECMO)
- E. Administer intravenous epinephrine
Explanation
The correct answer is:
- D. Start extracorporeal membrane oxygenation (ECMO)
This patient is presenting with severe hypothermia (core temperature <28°C) and significant bradycardia. According to Canadian guidelines, patients with stage III-IV hypothermia should be considered for extracorporeal life support (ECLS), such as ECMO. This approach provides both circulatory support and rapid core rewarming.
Option A is insufficient for severe hypothermia. Option B is incorrect as chest compressions are not immediately indicated in a patient with a pulse, even if bradycardic. Option C (peritoneal lavage) is less effective than ECMO for severe cases. Option E (epinephrine) is not recommended as the first-line treatment in severe hypothermia due to the risk of inducing arrhythmias.
References
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Dow J, Giesbrecht GG, Danzl DF, et al. Wilderness Medical Society Clinical Practice Guidelines for the Out-of-Hospital Evaluation and Treatment of Accidental Hypothermia: 2019 Update. Wilderness Environ Med. 2019;30(4S):S47-S69.
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Strapazzon G, Procter E, Paal P, Brugger H. Pre-hospital core temperature measurement in accidental and therapeutic hypothermia. High Alt Med Biol. 2014;15(2):104-111.
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Canadian Medical Association Journal. Accidental hypothermia. CMAJ. 2020;192(8):E184-E194.
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Public Health Agency of Canada. Cold Weather Health Information. Available at: https://www.canada.ca/en/health-canada/services/healthy-living/your-health/environment/extreme-cold.html (opens in a new tab)
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Brown DJA, Brugger H, Boyd J, Paal P. Accidental hypothermia. N Engl J Med. 2012;367(20):1930-1938.