Environmental Emergencies — Heat Stroke, Hypothermia, Drowning

📕 1 · Tintinalli's Emergency Medicine, 9th Ed

Tintinalli's Summary — Temperature Is the Treatment Target

"In both heat stroke and accidental hypothermia, the defining derangement is core temperature, and the central principle is the same: correct the temperature while supporting the failing organ systems. In heat stroke, every minute the core remains above 40°C causes ongoing cellular injury — so cooling is the resuscitation, and it must be rapid. In hypothermia, the dictum 'no one is dead until warm and dead' governs prolonged resuscitation, because profound hypothermia is neuroprotective."

Tintinalli's Emergency Medicine: A Comprehensive Study Guide, 9th Ed. McGraw-Hill 2020. Section: Environmental Injuries.

The Core Message (Tintinalli's)

Heat stroke = hyperthermia (core >40°C) + CNS dysfunction (altered mentation, seizures, coma). It is a clinical diagnosis and a true emergency — cool first, cool fast.
Antipyretics do NOT work in heat stroke — the hypothalamic set-point is normal; the problem is failed heat dissipation, not a raised set-point.
Accidental hypothermia: handle gently (irritable myocardium → VF), rewarm by severity, and continue resuscitation until rewarmed — "not dead until warm and dead."
Drowning: the priority is reversing hypoxia — start with airway and rescue breaths/ventilation; the lung injury, not the water "type", drives the course.

🔥 Heat Stroke — The One Rule

Cool to ~39°C, then stop. Cold-water immersion is the fastest, most effective method for exertional heat stroke. Begin cooling immediately — do not delay for transport or investigations. Stop active cooling at ~38.5–39°C to avoid overshoot hypothermia.

📘 2 · Rosen's Emergency Medicine, 10th Ed

Rosen's — Thermoregulation & Why Organs Fail

"Heat stroke represents the failure of thermoregulatory compensation, with a transition from heat exhaustion to a systemic inflammatory response resembling sepsis. Direct cytotoxicity above 40°C, combined with an exaggerated inflammatory and coagulation cascade, produces a multi-organ syndrome: encephalopathy, rhabdomyolysis, acute kidney injury, hepatic injury, and disseminated intravascular coagulation. Mortality correlates with the duration and magnitude of hyperthermia."

Rosen's Emergency Medicine: Concepts and Clinical Practice, 10th Ed. Elsevier 2023. Chapter: Heat Illness & Cold Injuries.

📘 Rosen's — Classic vs Exertional Heat Stroke

Classic (non-exertional): elderly, chronically ill, during heat waves; impaired thermoregulation/medications (anticholinergics, diuretics); often anhidrotic (dry skin); develops over days. The dominant pattern in Indian summer heat-wave deaths.
Exertional: young, healthy (athletes, soldiers, labourers); intense exertion in heat; often still sweating; rapid onset; higher rates of rhabdomyolysis, AKI, DIC, and hepatic failure. Cold-water immersion is most clearly life-saving here.

📘 Rosen's — The "Afterdrop" & Rescue Collapse in Hypothermia

During rewarming, cold peripheral blood returns to the core, causing a paradoxical further fall in core temperature ("afterdrop") and a drop in BP as vasodilatation occurs. Rough handling or sudden movement of a severely hypothermic patient can precipitate ventricular fibrillation in an irritable myocardium ("rescue collapse"). This is why severe hypothermia mandates gentle handling, horizontal positioning, core rewarming, and continued CPR/resuscitation until the core is rewarmed.

🔥 3 · Heat Stroke

Management of Heat Stroke (Cool First)

Cooling — The Resuscitation

Exertional heat stroke: cold-water (ice-water) immersion is first-line — fastest cooling rate, best survival WMS / sports medicine. Where immersion is impractical (classic heat stroke, elderly, multi-line patients): evaporative cooling (spray tepid water + continuous fans) ± ice packs to neck/axillae/groin, cold IV fluids. Target core ~39°C, then stop active cooling. Use a continuous core (rectal/oesophageal) thermometer.

Control Shivering & Support Organs

Shivering generates heat and opposes cooling — control with benzodiazepines (also for seizures/agitation). Manage the multi-organ syndrome: IV fluids for hypotension (cautious — often vasodilated, not just dry), watch for rhabdomyolysis (CK, dark urine → fluids ± alkalinisation), AKI, DIC, hepatic injury, electrolyte derangements. Antipyretics (paracetamol/aspirin) are ineffective and potentially harmful (hepatotoxicity, coagulopathy) — do not use.

📘 Heat Stroke Mimics — Don't Miss These

Hyperthermia + altered mentation is also produced by neuroleptic malignant syndrome (dopamine antagonists, lead-pipe rigidity), serotonin syndrome (serotonergic drugs, clonus/hyperreflexia — treat with cyproheptadine), malignant hyperthermia (volatile anaesthetics/suxamethonium — dantrolene), thyroid storm, anticholinergic toxidrome, and sepsis/CNS infection. The history and exam (rigidity vs clonus vs dry skin) distinguish them; all need cooling plus the specific antidote.

❄️ 4 · Accidental Hypothermia

Staging & Rewarming

Mild (32–35°C)

Shivering, tachycardia, confusion. Passive external rewarming.

Moderate (28–32°C)

Shivering stops, bradycardia, ↓consciousness, J (Osborn) waves. Active external + minimally invasive.

Severe (<28°C)

Coma, hypotension, arrhythmia/VF risk. Active internal/ECLS rewarming.

❄️ "Not Dead Until Warm and Dead"

Hypothermia is neuroprotective — full neurological recovery has occurred after prolonged cardiac arrest with core temperatures in the low 20s°C. Continue CPR and do not pronounce death until the core is rewarmed (≥32–35°C), especially in immersion/avalanche victims. A serum potassium >~12 mmol/L (asphyxial death/cell lysis) is a recognised marker of non-survivability that may guide termination in the rewarmed-or-rewarming patient.

Rewarming Methods by Severity

Passive external: remove wet clothes, insulate, warm environment (mild).
Active external: forced-air warming blankets, radiant heat, heat packs to trunk (avoid limbs first → afterdrop).
Active internal/minimally invasive: warmed humidified O₂, warmed IV fluids (40–42°C), body-cavity lavage.
Extracorporeal (ECLS/ECMO or cardiopulmonary bypass): the treatment of choice for hypothermic cardiac arrest / severe instability — fastest, controlled rewarming with circulatory support.

Arrest & Drug Modifications in Severe Hypothermia (ERC 2021)

The hypothermic heart may be unresponsive to drugs and defibrillation until rewarmed. If core <30°C: withhold resuscitation drugs; limit defibrillation to 3 shocks until temperature rises. 30–35°C: double the interval between drug doses. Handle gently, keep horizontal, rewarm — then resume standard ALS as the core normalises.

🌊 5 · Drowning & Electrical Injury

Drowning

Drowning — Reverse Hypoxia First

The pathophysiology is hypoxaemia from aspiration/laryngospasm — the historical "fresh vs salt water" distinction is clinically irrelevant. Resuscitation uniquely begins with airway and ventilation/rescue breaths (5 initial breaths), then chest compressions — because the arrest is hypoxic. Provide high-flow O₂/CPAP/ventilation; expect delayed ARDS/pulmonary oedema (observe symptomatic patients). Treat associated hypothermia and consider c-spine injury only if mechanism suggests (diving). Asymptomatic patients with normal SpO₂ and exam after 4–8 h observation can be discharged.

Electrical Injury

Electrical & Lightning Injury

Current path and type matter more than the visible burn. Cardiac: arrhythmia/arrest (VF with AC, asystole with high-voltage DC/lightning) — monitor ECG. High-voltage and lightning cause deep tissue/muscle necrosis with rhabdomyolysis → aggressive IV fluids, monitor for compartment syndrome and AKI (myoglobinuria). Lightning is unique: prioritise those who appear "dead" (reverse triage) — asystole is often transient and responds to prompt CPR; fixed dilated pupils are unreliable. Watch for tympanic rupture, cataracts, and neurological sequelae.

🇮🇳 Indian Context

Heat waves cause large seasonal mortality (NDMA Heat Action Plans); classic heat stroke in the elderly, outdoor labourers, and during power cuts is common — prevention messaging and rapid evaporative cooling in EDs are key.

Lightning is a leading cause of environmental/natural-disaster death in India (agricultural workers in open fields). Drowning is common (open water bodies, monsoon floods, lack of supervision).

Hypothermia is underestimated — seen in northern winters, high-altitude exposure, the homeless, the elderly, and as a secondary complication of trauma/sepsis even in warm climates (don't only think of it in the cold).

💊 6 · Drugs & Quick Flowchart

Drug Reference — Environmental Emergencies

Drug	Indication	Dose	Notes
Cold IV fluids (0.9% saline)	Heat stroke cooling + volume	Cooled crystalloid boluses, titrate to BP	Adjunct to surface cooling; cautious — vasodilated
Benzodiazepine (diazepam/lorazepam)	Shivering, seizures, agitation	e.g. lorazepam 2–4 mg IV	Shivering opposes cooling; also for serotonin syndrome agitation
Dantrolene	Malignant hyperthermia (NOT heat stroke)	2.5 mg/kg IV, repeat to 10 mg/kg	No proven benefit in classic/exertional heat stroke
Cyproheptadine	Serotonin syndrome	12 mg PO/NG then 2 mg q2h	Antiserotonergic; + cooling + benzodiazepines
Warmed IV fluids (40–42°C)	Hypothermia rewarming	Boluses via fluid warmer	Part of active internal rewarming
IV fluids ± bicarbonate	Rhabdomyolysis (heat/electrical)	Aggressive crystalloid; target urine output	Monitor CK, K⁺, renal function

ABC + measure core temperature

Continuous core (rectal/oesophageal) thermometer — surface temps mislead.
Airway/breathing/circulation support; cardiac monitor; bloods (CK, renal, coagulation, K⁺, glucose).

Correct the temperature

Heat stroke: cool immediately (immersion/evaporative) to ~39°C; control shivering.
Hypothermia: handle gently; rewarm by severity; ECLS for arrest/severe instability.

Treat complications & admit

Rhabdomyolysis/AKI, DIC, hepatic injury, electrolytes, arrhythmias.
Drowning → observe for delayed ARDS; electrical → ECG monitoring + compartment/rhabdo surveillance.

❌ 7 · Common Mistakes

Common Mistakes in Environmental Emergencies

❌ Mistake 1 — Giving Antipyretics for Heat Stroke

Paracetamol and aspirin do not lower temperature in heat stroke (the set-point is normal) and add hepatotoxicity and coagulopathy risk in a patient already prone to liver injury and DIC. The treatment is physical cooling, not antipyretics.

❌ Mistake 2 — Delaying Cooling for Transport/Tests

In heat stroke, time above 40°C is directly toxic. Begin aggressive cooling immediately at the point of care — do not wait for transfer, imaging or labs. "Cool first, cool fast", then continue investigations.

❌ Mistake 3 — Overshooting Into Hypothermia

Failing to stop active cooling leads to rebound hypothermia. Stop active cooling at ~38.5–39°C and monitor core temperature continuously.

❌ Mistake 4 — Rough Handling of the Hypothermic Patient

The severely hypothermic myocardium is highly irritable; rough movement can precipitate VF ("rescue collapse"). Handle gently, keep horizontal, and avoid unnecessary procedures until rewarming is underway.

❌ Mistake 5 — Pronouncing Death Before Rewarming

Hypothermia is neuroprotective — "not dead until warm and dead". Continue resuscitation and defer pronouncement until the core is rewarmed (or a marker of non-survivability such as K⁺ >12 is present). Apply drug/defibrillation modifications below 30°C.

❌ Mistake 6 — Discharging the Drowning Patient Too Early

Drowning can cause delayed pulmonary oedema/ARDS hours after the event. Observe symptomatic patients; only discharge those who remain asymptomatic with normal oxygenation and examination after an adequate observation period (≈4–8 h).

📑 8 · References

References

Tintinalli JE, Ma OJ, Yealy DM et al. Tintinalli's Emergency Medicine: A Comprehensive Study Guide, 9th Ed. Section: Environmental Injuries (Heat, Cold, Drowning, Electrical). McGraw-Hill; 2020.
Walls RM, Hockberger RS, Gausche-Hill M et al. Rosen's Emergency Medicine: Concepts and Clinical Practice, 10th Ed. Chapters: Heat Illness; Hypothermia; Drowning; Electrical & Lightning Injuries. Elsevier; 2023.
Lipman GS, Gaudio FG, Eifling KP et al. Wilderness Medical Society Clinical Practice Guidelines for the Prevention and Treatment of Heat Illness: 2019 Update. Wilderness Environ Med 2019;30(4S):S33–S46.
Dow J, Giesbrecht GG, Danzl DF et al. Wilderness Medical Society Clinical Practice Guidelines for the Out-of-Hospital Evaluation and Treatment of Accidental Hypothermia: 2019 Update. Wilderness Environ Med 2019;30(4S):S47–S69.
Lott C, Truhlář A, Alfonzo A et al. European Resuscitation Council Guidelines 2021: Cardiac arrest in special circumstances. Resuscitation 2021;161:152–219.
National Disaster Management Authority (NDMA), India. Guidelines for Preparation of Action Plan — Prevention and Management of Heat Wave.
Cameron P, Little M, Mitra B, Deasy C. Textbook of Adult Emergency Medicine, 5th Ed. Environmental Emergencies. Elsevier; 2019.