Frostbite 

 Introduction

Frostbite is a freezing cold injury caused by exposure of tissues to temperatures below the freezing point of skin (~–0.55°C). It results in ice crystal formation within tissues, leading to cellular injury, ischemia, and necrosis.

It is most commonly seen in extremities — fingers, toes, ears, nose, cheeks — and occurs due to prolonged exposure to cold, wet, and windy environments, often compounded by immobility, intoxication, or inadequate clothing.

Pathophysiology

Frostbite injury progresses through two main mechanisms:

1. Direct Cellular Damage

• Extracellular ice crystal formation draws water out of cells → cellular dehydration.
• With further cooling, intracellular ice crystals form → mechanical disruption of membranes and cell death.

2. Vascular and Reperfusion Injury

• Initial vasoconstriction → decreased perfusion → tissue hypoxia.
• Upon rewarming, reactive hyperemia and reperfusion injury occur, mediated by:
• Prostaglandins
• Thromboxanes
• Free radicals
• Endothelial injury → thrombosis → necrosis

This cascade closely resembles ischemia–reperfusion injury seen in burns and crush injuries.

Predisposing / Risk Factors

Classification

1. Traditional (Degrees) Classification

Analogous to burns:

 2. Clinical (Depth-based) Classification

Often used in modern emergency and military medicine:

• Superficial frostbite: skin and subcutaneous tissue affected; sensation intact after rewarming.
• Deep frostbite: muscle, tendon, bone involvement; sensation absent, tissues remain cold and hard after rewarming.

 Clinical Presentation

 Early (Before Rewarming)

• Numbness, tingling (“pins and needles”)
• Pale, cold, waxy skin
• Loss of fine motor coordination
• “Wooden” feel to extremities

 After Rewarming

• Skin becomes red, swollen, and painful
• Blister formation (clear or hemorrhagic)
• Tissue demarcation appears over days to weeks
• Eschar or gangrene in severe cases

 Differential Diagnosis

• Chilblains (Pernio) – inflammatory, not freezing
• Trench foot (immersion foot) – prolonged exposure to wet cold (>0°C)
• Burns (thermal/chemical)
• Peripheral arterial occlusion (embolism/thrombosis)

 Diagnosis

 Clinical Diagnosis

Frostbite is primarily clinical — based on history of cold exposure and characteristic lesions.

 Imaging

Used for prognosis and surgical planning (after rewarming):

 Emergency Management

 Step 1: Remove from Cold & Prevent Refreezing

• Move patient to warm environment.
• Refreezing after thawing causes exponentially worse injury → must ensure thawed tissues stay warm.

 Step 2: Rapid Rewarming

• Immerse affected part in circulating warm water (37–39°C) for 15–30 minutes until tissue becomes soft and pliable.
• Avoid dry heat, rubbing, or friction → worsens injury.

 Step 3: Pain Management

• NSAIDs (e.g., Ibuprofen) reduce pain and inhibit thromboxane-mediated vasoconstriction.
• Opioids for severe pain during rewarming.

 Step 4: Wound Care

• Aspirate clear blisters (to remove prostaglandin-rich fluid).
• Leave hemorrhagic blisters intact.
• Apply Aloe vera cream q6h (antiprostaglandin effect).
• Use loose, sterile dressings and elevate the limb.

 Step 5: Supportive Care

• Maintain normothermia and hydration.
• Tetanus prophylaxis.
• Avoid smoking / vasoconstrictors (nicotine, caffeine).

 Advanced / Hospital Management

 Thrombolysis and Vasodilator Therapy

Used in deep frostbite with vascular compromise within 24 hours of injury:

Contraindications: bleeding diathesis, recent surgery, trauma, or uncontrolled hypertension.

 Surgical Management

• Avoid early amputation — demarcation may take 3–6 weeks.
• Debridement / amputation only after clear line of demarcation or when wet gangrene or sepsis occurs.
• Sympathectomy or hyperbaric oxygen therapy (HBOT) may be considered experimentally in salvage attempts.

 Complications

 Prognosis

• Good prognosis in superficial frostbite with early rewarming.
• Poor prognosis indicators:
• Hard, black, or insensate tissue post-rewarming
• Hemorrhagic blisters
• Absence of capillary refill or Doppler flow after 48 hrs
• Tissue loss correlates with delay in rewarming and refreezing episodes.

 Prevention

• Layered, moisture-wicking clothing
• Avoid tight boots or gloves
• Keep dry and change wet clothes
• Avoid alcohol, smoking, and unnecessary exposure
• Monitor for early signs — numbness, tingling, pallor

 Key References

• Harrison’s Principles of Internal Medicine, 21st ed.
• StatPearls: Frostbite (2024 update)
• McIntosh SE et al. Wilderness Med Soc Practice Guidelines for Frostbite. Wilderness Environ Med. 2019.
• Cauchy E, et al. “Management of Severe Frostbite: A Review.” N Engl J Med. 2021.