Algorithm

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graph TD

classDef start fill:#1b5e20,color:#ffffff,stroke:#66bb6a;
classDef step fill:#0d47a1,color:#ffffff,stroke:#42a5f5;
classDef decision fill:#4a148c,color:#ffffff,stroke:#ab47bc;
classDef alert fill:#b71c1c,color:#ffffff,stroke:#ef5350;

A(<b>Cold Exposure</b><br>Initial Assessment):::start
B{<b>Injury Category</b>}:::decision

A --> B

B -->|Systemic| C[<b>Accidental Hypothermia</b><br>Core temp under 35C]:::step
B -->|Localized| D[<b>Soft Tissue Injury</b><br>Extremities and exposed skin]:::step
B -->|Recurrent| E[<b>Genetic Syndromes</b><br>Investigate for auto-inflammation]:::step

C --> F{<b>Clinical Stage</b>}:::decision

F -->|Mild 32 to 35C| G[<b>Mild Hypothermia</b><br>Shivering intact]:::alert
F -->|Mod 28 to 32C| H[<b>Moderate Hypothermia</b><br>Stupor and decreased pulse]:::alert
F -->|Severe Under 28C| I[<b>Severe Hypothermia</b><br>Coma and bradycardia]:::alert

G --> M[<b>Passive Rewarming</b><br>Remove wet clothes and insulate]:::step
H --> N[<b>Active Rewarming</b><br>Forced air and warmed IV fluids]:::step
I --> O[<b>Internal Rewarming</b><br>Check pulse 1 min and warm blood]:::step

D --> J{<b>Tissue Status</b>}:::decision

J -->|Freezing| K[<b>Frostbite I to IV</b><br>Ice crystal formation]:::alert
J -->|Non Freezing| L[<b>Frostnip or Chilblains</b><br>Edema and no necrosis]:::alert

K --> P[<b>Rapid Rewarming</b><br>Circulating bath 37 to 39C]:::step
L --> Q[<b>Conservative Mgmt</b><br>Rewarm and topical creams]:::step

General Principles

• Occurs when physiological heat generation fails to overcome environmental heat loss.
• Develops even at temperatures above 0°C.
• Heat transfers to environment via radiation, conduction, convection, respiration, and evaporation.
• Categorized broadly into systemic injuries (accidental hypothermia) and localized soft tissue injuries (freezing and non-freezing).

Systemic Injury: Accidental Hypothermia

Definition And Pathophysiology

• Defined as unintentional core body temperature drop below 35°C.
• Cerebral function diminishes at 33-34°C.
• Early manifestations include irritability, confusion, and poor decision-making.
• Progresses to lethargy, somnolence, and coma.

Clinical Staging And Characteristics

Emergency Management

General Measures

• Handle gently and keep horizontal to prevent cardiovascular collapse.
• Remove wet clothing immediately.
• Replace with dry clothing and insulation to halt heat loss.

Mild Hypothermia Management (32-35°C)

• Initiate passive rewarming using insulation and vapor barriers.
• Provide active external rewarming with heat packs applied to neck, chest, upper torso, axilla, and groin.
• Protect exposed skin from direct burns.
• Support shivering with high-calorie oral fluids and carbohydrates if child remains alert.

Moderate Hypothermia Management (28-32°C)

• Deploy active external rewarming to upper torso, chest, axilla, and back utilizing forced-air systems or large heat pads.
• Administer intravenous or intraosseous fluids containing glucose, warmed to 40-42°C.
• Maintain continuous cardiac monitoring due to high risk of unstable arrhythmias from cold heart and acidosis.
• Transfer hemodynamically unstable patients to facilities capable of extracorporeal membrane oxygenation.

Severe Hypothermia (<28°C) And Cardiac Arrest

• Assess pulse for up to 1 minute before initiating cardiopulmonary resuscitation.
• Utilize bedside echocardiogram to detect organized electrical activity.
• Initiate cardiopulmonary resuscitation for absent cardiac activity.
• Never withhold cardiopulmonary resuscitation based on temperature unless fatal injury exists or chest compression proves impossible.
• Hold vasoactive medications until core temperature exceeds 30°C.
• Administer vasoactive medications at twice normal dosing interval between 30°C and 35°C.
• Attempt single defibrillation or cardioversion at maximum power.
• Hold further electrical shocks until core temperature exceeds 30°C.
• Initiate active internal rewarming via warm intravenous fluids, extracorporeal blood warming, or hemodialysis alongside extracorporeal membrane oxygenation.

Localized Soft Tissue Cold Injuries

Freezing Cold Injury: Frostbite

Pathogenesis

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

Clinical Grading Of Frostbite

Management Of Frostbite

• Protect injured area from cold exposure.
• Remove constricting items including jewelry.
• Strictly prevent refreezing if spontaneous thawing commences.
• Initiate rapid rewarming using circulating water bath heated to 37-39°C for 30 minutes.
• Leave clear blisters intact.
• Never aspirate hemorrhagic bullae.
• Administer pain control medications.
• Ensure updated tetanus prophylaxis.
• Consider adjuvant therapies for severe cases 12-72 hours post-thawing.
• Adjuvant options include vasodilators, antiplatelet drugs, synthetic prostacyclin analogues, or intra-arterial tissue plasminogen activator.

Non-Freezing Cold Injuries

Frostnip

• Associated with vasoconstriction and superficial ice crystal formation.
• Presents with localized numbness and pallor.
• Lacks cellular damage.
• Resolves rapidly upon external warming.

Chilblains (Pernio)

• Idiopathic condition triggered by cold, damp exposure.
• Presents as painful, edematous, bluish-red papular or nodular lesions.
• Affects acral locations including fingers, toes, and ears.
• Management requires rewarming, cold avoidance, nonsteroidal anti-inflammatory drugs, and topical soothing creams.

Cold-Induced Fat Necrosis

• Results from local cold injury to superficial adipose tissue.
• Presents as raised, erythematous nodules or plaques.
• Appears on face or exposed areas in obese children.
• Follows self-limiting course resolving in 10-20 days.
• Managed conservatively with rewarming and nonsteroidal anti-inflammatory drugs.

Differential Diagnosis: Genetic And Autoinflammatory Syndromes

• Evaluate children presenting with recurrent cold-induced symptoms very early in life.
• Suspect underlying genetics when rashes, fevers, and arthralgias occur without infectious triggers.

Familial Cold Autoinflammatory Syndrome

• Represents part of cryopyrin-associated periodic syndromes.
• Caused by variants in NLRP3 gene.
• Triggered exclusively by cold exposure.
• Manifests with nonpruritic urticaria, fever, conjunctivitis, and joint pain.

Familial Chilblain Lupus

• Inherited as autosomal dominant disorder.
• Caused by variants in TREX1 or SAMHD1 genes.
• Presents with painful, bluish-red acral lesions resembling chilblains.
• Provoked by environmental cold exposure.

Crisponi Syndrome / Cold-Induced Sweating Syndrome

• Inherited as autosomal recessive disorder.
• Linked to CRLF1 or CLCF1 gene variants.
• Presents with cold-induced profuse sweating.
• Associated with feeding difficulties and facial dysmorphic features.