Author:
Christina O.Foreman
Description
- Tissue damage caused by cold temperature exposure
- Mechanism:
- Tissue damage results from:
- Direct cell damage: Intracellular ice crystal formation
- Indirect cell damage: Extracellular ice crystal formation leads to intracellular dehydration and enzymatic disruption
- Reperfusion injury: Occurs upon rewarming. Fluid rich in inflammatory mediators (prostagland in and thromboxane) extravasates through damaged endothelium promoting vasoconstriction and platelet aggregation
- Clear blisters from extracellular exudation of fluid
- Hemorrhagic blisters occur when deeper subdermal vessels are disrupted, indicating more severe tissue injury
- The end result is arterial thrombosis, ischemia, and ultimately, necrosis
- Devitalized tissue demarcates as the injury evolves over weeks to months, hence the phrase “frostbite in January, amputate in July”
Etiology
- Cold exposure: Duration of exposure, wind chill, humidity, and wet skin and clothing all increase the likelihood of frostbite
- Predisposing factors:
- Extremes of age
- Altered mental status (intoxication or psychiatric illness)
- Poor circulatory status
Signs and Symptoms
- Extremities (fingers, toes) and head (ears, nose) most commonly affected
- After rewarming frostbite can be classified; however, initial classification often fails to provide an accurate prognosis and does not alter initial management
- Superficial frostbite:
- Only skin structures involved. Usually no tissue loss
- First degree: Erythema and edema with stinging, burning, and throbbing. No blisters or necrosis
- Second degree: Significant edema, clear blister formation. Numbness common
- Deep frostbite:
- Tissue loss inevitable
- Third degree: Involves subcutaneous tissue. Hemorrhagic blister formation due to subdermal venous plexus injury:
- Initially insensate, injuries develop severe pain/burning on rewarming
- Fourth degree: Involves muscle, tendon, and bone. Initially mottled, deep red, or cyanotic
- Unfavorable prognostic indicators include: Hemorrhagic blisters, persistent cyanosis, mottling, anesthesia, and reduced mobility after rewarming
- Devitalized tissue demarcates as the injury evolves over weeks to months forming skin necrosis and dry black eschar
Essential Workup
- Diagnosis is based on the clinical presentation. Wound description should include skin color and temperature, blister formation and color, and soft tissue consistency
- A neurologic and vascular exam should include pulses (by Doppler if necessary), cap refill, and 2-point discrimination
- Look for underlying factors contributing to cold exposure and comorbid conditions requiring emergency management:
- Hypothermia
- Trauma
- Hypoglycemia
- Cardiac or neurologic problems
- Intoxication/overdose
- Compartment syndrome
Diagnostic Tests & Interpretation
Lab
- None indicated in mild cases
- For deep frostbite:
- CBC
- Electrolytes, BUN/creatinine, glucose
- Urinalysis/CK for evidence for myoglobinuria
- Cultures and Gram stains from open areas when infection suspected
Imaging
Technetium-99 scintigraphy or MRA:
- May be helpful in early identification of salvageable vs. unsalvageable tissue
- Permits earlier decision about amputation
Diagnostic Procedures/Surgery
Method to create a warm water bath in the ED:
- Whirlpool hydrotherapy ideal; however, most EDs do not have
- Mix hot and cold tap water from a stand ard hospital sink in a large basin
- Use a thermometer to keep temperature between 40°-42°C
- The water will cool quickly: Intermittently add warm water or replace the water to keep the temperature in the proper range
- Warmer temperatures can cause thermal injury while cooler temperatures delay thawing and decrease tissue survival
Differential Diagnosis
- Frostnip:
- Superficial, reversible ice crystal formation without tissue destruction
- Transient numbness and paresthesia resolve after dry rewarming
- Trench (immersion) foot:
- Exposure to wet cold for prolonged periods
- Neurovascular damage without ice crystal formation
- Pallor, mottling, paresthesias, pulselessness, paralysis, and numbness
- May be difficult to distinguish from postthaw phase of frostbite
- Hyperemia with dry rewarming may last up to 6 wk
- Chilblains:
- Chronic repeated exposure to dry cold
- Localized erythema, cyanosis, plaques, and vesicles
- Recurrent episodes common in patients with underlying vasculitis
- Symptomatic treatment, dry rewarming
Prehospital
- Protect and immobilize frostbitten area during transport
- Remove restrictive or wet garments
- Avoid dry rewarming of the frostbitten limb if there is a likelihood of refreezing injury during transport
- If evacuation will be delayed and suitable facilities are available, field rewarming in warm (40°-42°C) water can be attempted
- Rubbing, manipulating the limb, or applying snow while it is still frozen is contraindicated
ALERT |
- Hypothermia:
- Common in frostbite victims
- In the severely hypothermic patient, avoid rough hand ling to minimize risk of cardiac dysrhythmias
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Initial Stabilization/Therapy
- ABCs management
- Identify and correct hypothermia
- IV fluid volume expansion with 0.9% NS for severe frostbite
- Protect frostbitten areas from excessive hand ling during resuscitation
ED Treatment/Procedures
- If the injury is <24 hr old and has not yet been rewarmed:
- Initiate rapid rewarming of the frostbitten extremity in a 40°-42°C water bath for 15-30 min
- Stop treatment when the limb is warm, red, and pliable
- Monitor water temperature closely to prevent thermal injury
- Analgesia: IV morphine
- NSAIDs (e.g., ibuprofen) to combat the effects of prostagland ins on skin necrosis
- Aloe vera topical cream:
- Recommended for all intact blisters
- Combats the arachidonic acid cascade
- Avoid preparations containing alcohol, scent, salicylates, all of which interfere with aloe effectiveness
- Blister debridement or aspiration:
- Indicated for clear blebs:
- Removes thromboxane and prostagland ins
- Contraindicated for hemorrhagic blebs:
- Exposes deeper structures to dehydration and infection
- Tetanus prophylaxis
- Antibacterial prophylaxis:
- Consider during the hyperemic recovery phase (at least 2-3 d) in severely frostbitten areas
- Against Streptococci, Staphylococci, and Pseudomonas species (cephalosporin, penicillinase-resistant penicillin, quinolone)
- Topical antibacterial agents interfere with the use of aloe vera cream and should be considered a second-line approach
- Elevation and splinting of frostbitten area
- Change dressing 2-4 times daily
- Avoid vasoconstrictive agents (including tobacco)
- Adjunctive treatments include:
- Thrombolytic therapy (<24 hr of cold exposure):
- Both intra-arterial and systemic tPA may improve tissue salvage rates
- Consult with plastic/burn surgeon before treatment
- Vasodilator therapy:
Medication
- Aloe vera: Topical cream (70% concentration) q6h
- Cephalexin (cephalosporin): 500 mg (peds: 25-50 mg/kg/24 hr q6h) PO q.i.d
- Ciprofloxacin (quinolone): 500 mg PO b.i.d
- Dicloxacillin (penicillinase-resistant penicillin): 500 mg (peds: 12.5-25 mg/kg/24 hr q6h) PO q.i.d
- Ibuprofen (NSAID): 800 mg (peds: 40 mg/kg/24 hr q6-8h) PO t.i.d
- Morphine sulfate: 0.1-0.2 mg/kg (peds: 0.1 mg/kg) IV or IM p.r.n (titrate to patient response)
Disposition
Admission Criteria
- All but the most superficial cases should be admitted
- Lower admission threshold where risk of refreezing exists
- Immersion (trench) foot patients may be discharged only if an environment that allows for proper treatment can be provided
Discharge Criteria
Minimal superficial injury, all others should be admitted
Issues for Referral
General, burn, plastic, or hand surgeon should be consulted in all but the most superficial of cases
Follow-up Recommendations
All discharged patients should be referred to a general, burn, plastic, or hand surgeon
- Hand fordC, ThomasO, ImrayCHE, et al. Frostbite . Emerg Med Clin North Am. 2017;35(2):281-299.
- McIntoshSE, OpacicM, FreerL, et al. Wilderness Medical Society practice guidelines for the prevention and treatment of frostbite: 2014 Update . Wilderness Environ Med. 2014;25(4 Suppl):S43-S54.
- MurphyJV, BanwellPE, RobertsAH, et al. Frostbite: Pathogenesis and treatment . J Trauma. 2000;48(1):171-178.
See Also (Topic, Algorithm, Electronic Media Element)
Hypothermia
The authors gratefully acknowledge Joseph M. Weber for his contribution to the previous edition of this chapter.