Approach to a child with cold injury

General Principles of Cold Injuries

• Cold injuries occur when the body's physiological ability to generate heat is overwhelmed by environmental heat loss, which happens even at temperatures above $0^{\circ }C$ (${32}^{\circ }F$).
• Heat transfer to the environment is governed by five mechanisms: radiation, conduction, convection, respiration, and evaporation.
• Cold injuries are broadly categorized into systemic injuries (accidental hypothermia) and localized soft tissue injuries (freezing and non-freezing),.

Accidental Hypothermia

• Accidental hypothermia is defined as an unintentional drop in core body temperature below ${35}^{\circ }C$ (${95}^{\circ }F$).
• Cerebral function begins to diminish at a core temperature of $33-{34}^{\circ }C$, manifesting early as irritability, confusion, and poor decision-making, which progresses to lethargy, somnolence, and coma.

Clinical Staging and Characteristics

• The presentation of hypothermia progresses through physiological zones based on core temperature,.

Emergency Management of Hypothermia

• Patients with any degree of hypothermia must be handled gently and kept horizontal to prevent cardiovascular collapse.
• Wet clothing must be removed and replaced with dry clothing and insulation to prevent further heat loss,.
• Mild Hypothermia ($32-{35}^{\circ }C$):
  • Initiate passive rewarming by applying insulation (e.g., sleeping bags) and a vapor barrier.
  • Provide active external rewarming using hot water bottles or heat packs applied to the neck, chest, upper torso, axilla, and groin, ensuring exposed skin is protected from burns.
  • Support shivering with high-calorie oral fluid and carbohydrate replacement if the child is alert and can protect their airway,.
• Moderate Hypothermia ($28-{32}^{\circ }C$):
  • Initiate active external rewarming to the upper torso, chest, axilla, and back (e.g., forced-air systems, large heat pads),.
  • Administer intravenous (IV) or intraosseous (IO) fluids, ideally containing glucose, warmed to $40-{42}^{\circ }C$,,.
  • Perform continuous cardiac monitoring, as a cold heart combined with acidosis increases the risk of unstable arrhythmias.
  • If hemodynamically unstable, transfer to a facility capable of extracorporeal membrane oxygenation (ECMO).
• Severe Hypothermia ($<{28}^{\circ }C$) and Cardiac Arrest:
  • Assess for a pulse for up to $1$ minute or look for organized electrical activity on a monitor/bedside echocardiogram before initiating cardiopulmonary resuscitation (CPR).
  • Initiate CPR if cardiac activity is absent; do not withhold CPR based on temperature unless there is obvious fatal injury or chest wall compression is impossible,.
  • Vasoactive medications (e.g., epinephrine) should be held until the core temperature reaches $>{30}^{\circ }C$; once $>{30}^{\circ }C$, administer at twice the normal dosing interval until the core temperature reaches ${35}^{\circ }C$,.
  • Attempt defibrillation or cardioversion once at maximum power; if unsuccessful, further shocks should be held until the core temperature is $>{30}^{\circ }C$,.
  • Active internal rewarming (e.g., warm IV fluids, extracorporeal blood warming, hemodialysis) is indicated alongside ECMO for cardiopulmonary support,.

Soft Tissue Cold Injuries

Freezing Cold Injury: Frostbite

• Frostbite occurs at or below freezing temperatures and progresses through four phases: prefreeze, freeze-thaw, vascular stasis, and late ischemic,.
• Cellular destruction primarily results from intracellular and extracellular ice crystal formation during the freeze-thaw phase, followed by ischemic-reperfusion injury and microvascular thrombosis,.

Clinical Grading of Frostbite

• Frostbite is classified based on the depth of tissue injury after the tissue has thawed.

Management of Frostbite

• Protect the injured area from the cold, remove constricting items (e.g., jewelry), and strictly prevent refreezing if spontaneous thawing has begun.
• Initiate rapid rewarming using a circulating water bath heated to $37-{39}^{\circ }C$ for $30$ minutes,.
• Do not break clear blisters and do not aspirate hemorrhagic bullae.
• Administer pain control medications (e.g., ibuprofen) and ensure tetanus prophylaxis is up to date,.
• Depending on severity and duration since thawing ($12-72$ hours), adjuvant therapies may be initiated, including vasodilators (papaverine), antiplatelet drugs, synthetic prostacyclin analogues (iloprost), or intra-arterial tissue plasminogen activator (tPA),,.

Non-Freezing Cold Injuries

• Frostnip: Associated with vasoconstriction and superficial ice crystals (frost) on the skin surface; presents with numbness and pallor but no cellular damage; resolves rapidly upon warming.
• Chilblains (Pernio): An idiopathic condition presenting as painful, edematous, bluish-red papular or nodular lesions on acral locations (fingers, toes, ears) after exposure to cold, damp conditions,,.
  • Treatment involves rewarming, avoidance of cold, and nonsteroidal anti-inflammatory drugs (NSAIDs) or topical soothing creams.
• Cold-Induced Fat Necrosis: Secondary to local cold injury to superficial adipose tissue; presents with raised, erythematous nodules or plaques on the face (cheeks/forehead) or exposed areas in obese children (thighs, buttocks).
  • Lesions are self-limiting, typically resolving in $10-20$ days, and are managed with rewarming and NSAIDs for discomfort.

Differential Diagnosis and Genetic Considerations

• Children presenting with recurrent cold-induced symptoms (rashes, fevers, arthralgias) very early in life without an infectious trigger must be evaluated for cold-induced autoinflammatory syndromes,.
• Familial Cold Autoinflammatory Syndrome (FCAS): Part of the cryopyrin-associated periodic syndromes (CAPS), caused by variants in the NLRP3 gene; triggered by cold exposure, resulting in nonpruritic urticaria, fever, conjunctivitis, and joint pain.
• Familial Chilblain Lupus: An autosomal dominant disorder caused by variants in TREX1 or SAMHD1 genes; presents with painful, bluish-red acral lesions resembling chilblains, triggered by cold exposure.
• Crisponi Syndrome / Cold-Induced Sweating Syndrome (CS/CISS): An autosomal recessive disorder (CRLF1 or CLCF1 variants) presenting with cold-induced profuse sweating, feeding difficulties, and dysmorphic features.