High Yield Topics

Hypothermia and Frostbite

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Ovid: 5-Minute Sports Medicine Consult, The


Hypothermia and Frostbite
Rania L. Dempsey
Craig C. Young
Basics
Description
  • Frostbite:
    • Severe local cold-related injury resulting in freezing of soft tissue:
      • Superficial: Partial or complete freeze of skin
      • Deep: Involvement of skin and underlying tissue (may include muscles, vessels, nerves, fat, and bone)
  • Hypothermia:
    • Systemic cold injury, classified as:
      • Mild: Core body temperature 32–35°C (90–95°F)
      • Moderate: 30–32°C (86–90°F)
      • Severe: <30°C (86°F)
Epidemiology
Incidence
  • True incidence of hypothermia and frostbite is unknown in athletes:
    • Mild cases of both are likely common in cold environments.
    • Hypothermia reported in up to 69% of athletes in cold water swimming events (1).
  • Annual incidence of hypothermia-related deaths 4 per 1,000,000 general population in the U.S. (2):
    • More common in men (67% of hypothermia deaths) and those aged ≥65 yrs (49% of hypothermia deaths)
Risk Factors
  • Hypothermia:
    • Environmental factors: Cold temperature, wind chill, prolonged exposure, high altitude
    • Wet clothing (increases heat loss 2–5 times) or immersion (increases heat loss 10–25 times)
    • Fatigue
    • Low body fat
    • Alcohol use (inhibits shivering, enhances heat loss through peripheral vasodilation, and may lead to false sense of warmth)
    • Extremes of age (very young or old)
    • Underlying medical disease (eg, sickle cell anemia, peripheral vascular disease, diabetes, seizure disorder, hypothyroidism)
    • Use of neuroleptic drugs
  • Frostbite:
    • Environmental factors:
      • Cold temperature, wind chill, prolonged exposure, high altitude
        • Risk of frostbite is <5% with temperatures >5°F (-15°C), but significant risk of frostbite increases with temperatures ≤18°F (-27°C) (3).
    • Wet clothing (increases heat loss 2–5 times) or immersion (increases heat loss 10–25 times)
    • Prior cold injury
    • Petroleum or oil lubricants
    • Constrictive clothing
    • Smoking
    • Vasospastic disorders, ie, Raynaud's syndrome
General Prevention
Best treatment for hypothermia and frostbite is prevention (3)[C]:
  • Event planning based on the potential temperature ranges
  • Proper clothing, including hats, mittens, and multiple layers, as necessary
  • Avoid alcohol and other mood-altering drugs.
  • Recognize the signs and symptoms of hypothermia that indicate a need to seek shelter (shivering, slurred speech, somnolence)
Etiology
  • Frostbite:
    • Fluids in body tissues and cellular spaces freeze and crystallize.
    • Cyclic vasodilation and vasoconstriction contribute to hypoxia/ischemia of affected tissue
    • Severe or prolonged exposure can lead to irreversible tissue damage.
  • Hypothermia:
    • Body heat is lost to the environment at a rate that overwhelms normal temperature homeostasis, resulting in decreased core body temperature.
    • With decreasing temperature, heart rate, cardiac output, and cerebral blood flow decrease:
      • May lead to cardiac rhythm disturbance and death
Diagnosis
  • Frostbite:
    • Skin may appear erythematous and swollen, or waxy, white, yellow, or blue-purple.
    • Vesicles/blisters may be present.
    • Patients with superficial frostbite complain of numbness and pain in affected area, but in severe/deep frostbite, pain may be absent.
  • Hypothermia:
    • Mild: Patient displays shivering and mild mental status changes, including confusion, amnesia, dysarthria, and ataxia.
    • Moderate: As core temperature declines, patient may develop severely impaired judgment or stupor, loss of deep tendon reflexes, loss of shivering with muscle rigidity, and cardiac arrhythmias.
    • Severe: Patient may have dilated pupils and appear comatose, with nearly undetectable BP and respiration.
History
  • Duration and severity of cold exposure (prolonged exposure to very cold temperatures increases risk of severe frostbite or hypothermia)
  • Recent alcohol or drug use (impairs judgment and increases susceptibility to cold injury)
  • History of cold water immersion (wet clothing and skin significantly increase continued heat loss)
  • Underlying medical conditions (increases risk of severe frostbite or hypothermia)
  • Pain in affected area suggests superficial vs deep frostbite.
Physical Exam
  • Measure core body temperature:
    • For greatest accuracy, should be taken rectally with a thermometer capable of measuring hypothermic temperatures (4)[A]
  • Assess pulse and cardiac rhythm:
    • Tachycardia may be seen with mild hypothermia.
    • May progress to bradycardia, atrial fibrillation, or ventricular fibrillation with more severe hypothermia
    • In severe hypothermia, may be difficult to manually palpate pulse
  • Assess mental status:
    • Degree of mental status alteration correlates with severity of hypothermia
  • Perform complete neurologic examination:
    • Intact sensation to pinprick indicates a better prognosis for patients with frostbite.
    • Decreased muscle coordination, delayed deep tendon reflexes, and slowed pupillary reflexes suggest more severe hypothermia.
    • Focal neurologic deficit suggests etiology of mental status changes other than hypothermia.
  • Inspect appearance of skin:
    • Cold, yellow-white, or purple skin suggests frostbite.
    • Tissue pliability suggests superficial frostbite; hard tissue without pliability suggests deep frostbite.
Diagnostic Tests & Interpretation
  • EKG: May see tachycardia; bradycardia; atrial fibrillation; ventricular fibrillation; prolonged PR, QRS, and QT intervals, and J waves (positive deflection occurring at junction of QRS complex and ST segment)
  • Electrolytes and basic chemistries: Hypothermic patients are at high risk for acid-base disturbances.
Differential Diagnosis
  • Frostbite:
    • Frostnip: Freezing injury to superficial skin layers
    • Trenchfoot: Swelling, cyanosis, and erythema of extremity without freezing of tissue
    • Chilblains: Local cold-related erythematous skin lesions
  • Hypothermia:
    • Altered mental status from metabolic abnormalities, alcohol/toxic ingestion, or closed head injury

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Treatment
Pre-Hospital
  • Frostbite:
    • Avoid thawing until no further risk of refreezing, then immerse affected part in 40°C (104°F) water for 15–30 min (5)[C].
    • Remove wet clothing and protect from further cold injury (5)[C].
    • Avoid rubbing or massaging skin, which may compound tissue damage (4,5)[A].
    • Monitor and treat for hypothermia (4)[C].
    • Arrange transport to medical facility for moderate or severe frostbite.
  • Hypothermia:
    • Mild:
      • Passive external rewarming: Prevent further heat loss with blankets, dry clothing, shared body heat, and moving patient to shelter (4)[C].
      • Active external rewarming: Direct application of heat sources (heating pad, hot water bottle, warm water immersion, electric blanket) applied to trunk and used cautiously. Application of heat sources to extremities can result in rapid reversal of cold-induced peripheral vasoconstriction, leading to hypotension (rewarming shock) and further decreases in core temperature (“afterdrop”).
      • Hot drinks for patients with normal gag reflex (4)[C].
      • Obtain rectal temperature when possible (4)[B]:
        • Athletes with oral or axillary temperatures >95°F are not likely to be hypothermic.
    • Moderate/severe: In addition to the above measures:
  • Active emergency medical system. Perform a primary survey and institute cardiopulmonary resuscitation (CPR) if needed (4)[C].
  • Attempts at field rewarming should not delay transport to emergency facility for patients with moderate or severe hypothermia (4)[C].
  • Avoid agitation or jarring due to high risk of arrhythmias (4)[B].
ED Treatment
  • Frostbite:
    • After rewarming, debride white blisters and apply topical aloe vera. For hemorrhagic blisters, apply aloe vera without debridement (5)[C].
  • Hypothermia (moderate or severe):
    • Continuous cardiac monitoring (6)[C]
    • Active external rewarming with forced-air rewarming blanket (6)[C]
    • Active internal rewarming with heated [43°C (109°F)] IV fluid or heated humidified air or oxygen (6)[C]:
      • Peritoneal, gastric, pleural, or bladder lavage with heated [40°C (104°F)] fluids may be used.
      • For severe cases, cardiopulmonary bypass may improve survival in young, otherwise healthy individuals.
    • Monitor electrolytes; rewarming usually corrects electrolyte and acid-base disturbances (6)[C].
    • Hypothermia with cardiac arrest requires a modified Advanced Cardiac Life Support protocol (hypothermic heart less responsive to defribrillation and cardioactive drugs; slowed drug metabolism with hypothermia) (7)[C]:
      • Establish airway; start CPR.
      • For ventricular fibrillation or ventricular tachycardia, attempt difibrillation once; withhold cardioactive drugs until core temperature >30°C but continue basic life support
      • For core temperature between 30°C and 34°C, administer cardioactive drugs with increased intervals between doses
Medication
  • Frostbite:
    • Administer tetanus prophylaxis and analgesics (5,6)[C].
    • Administration of penicillin G (500,000 U every 6 hr for 48–72 hr) prophylactically (5,6)[C]:
      • Controversial
    • Administration of intra-arterial tissue plasminogen activator within 24 hr of injury may decrease amputation rate (5,6,8)[B].
  • Hypothermia:
    • No evidence to support routine use of antibiotics, steroids, or barbiturates
Additional Treatment
Additional Therapies
Range of motion and strengthening exercises may benefit frostbite-affected limbs (5)[C].
Surgery/Other Procedures
Surgical debridement or amputation may be indicated for late treatment of necrotic or gangrenous tissue due to frostbite (6)[C].
Ongoing Care
Prognosis
  • Mild-to-moderate cases of both hypothermia and frostbite generally recover fully without complication.
  • Severe cases may lead to significant disability and death.
Complications
  • Frostbite:
    • Limb and digit loss
    • Premature closure of the epiphysis (younger athletes) (9)
    • Autonomic dysfunction of affected extremity
    • Permanent cold sensitivity and susceptibility to cold injury
  • Hypothermia:
    • Cardiac arrhythmias
    • Electrolyte and acid-base disorders
    • Inefficient clotting leading to disseminated intravascular coagulation
References
1. Brannigan D, Rogers IR, Jacobs I, et al. Hypothermia is a significant medical risk of mass participation long-distance open water swimming. Wilderness Environ Med. 2009;20:14–18.
2. Centers for Disease Control and Prevention (CDC). Hypothermia-related deaths–United States, 1999–2002 and 2005. MMWR Morb Mortal Wkly Rep. 2006;55:282–284.
3. Castellani JW, Young AJ, Ducharme MB, et al. Prevention of cold injuries during exercise. Med Sci Sports Exerc. 2006;38:2012–2029.
4. Cappaert TA, Stone JA, Castellani JW, et al. National Athletic Trainers' Association position statement: environmental cold injuries. J Athl Train. 2008;43:640–658.
5. Imray C, Grieve A, Dhillon S, et al. Cold damage to the extremities: frostbite and non-freezing cold injuries. Postgrad Med J. 2009;85:481–488.
6. Ulrich AS, Rathlev NK. Hypothermia and localized cold injuries. Emerg Med Clin North Am. 2004;22:281–298.
7. ECC Committee, Subcommittees and Task Forces of the American Heart Association. 2005 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation. 2005;112:IV1–IV203.
8. Bruen KJ, Ballard JR, Morris SE, et al. Reduction of the incidence of amputation in frostbite injury with thrombolytic therapy. Arch Surg. 2007;142:546–551; discussion 551–553.
9. Sallis R, Chassay CM. Recognizing and treating common cold-induced injury in outdoor sports. Med Sci Sports Exerc. 1999;31:1367–1373.
Codes
ICD9
  • 991.0 Frostbite of face
  • 991.3 Frostbite
  • 991.6 Hypothermia
Clinical Pearls
  • Hypothermia can occur even at moderate temperatures [50–65°F (10–18°C)] if wind, rain, sweat, or wet clothing lead to heat loss that is greater than metabolic heat production.
  • Prolonged exposure to cold temperatures, wet clothing, drug or alcohol use, and underlying medical conditions increase risk of hypothermia and frostbite.
  • Prevention is the best treatment for hypothermia and frostbite.
  • Avoid cotton clothing: It retains sweat, does not dry quickly, and provides very little insulation when wet:
    • Instead, use clothing made from wool or synthetic fabric.


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