Overview
This lecture covers environmental emergencies with a focus on heat-related (heat exhaustion, heat stroke, malignant hyperthermia) and cold-related conditions (frostbite, hypothermia), their differences, risk factors, prevention, assessment, and management.
Heat-Related Emergencies
- Heat exhaustion is due to dehydration from extreme heat (non-exertional or exertional).
- Symptoms: tachycardia, hypotension, dry mucous membranes, clammy/moist skin, and elevated labs (hematocrit, hemoglobin, BUN, creatinine).
- Heat exhaustion typically shows temperatures up to 102.5°F and responds to cooling.
- Heat stroke is a medical emergency; body temperature rises above 104°F, and heat loss mechanisms fail.
- Signs of heat stroke: confusion, mental status changes, usually no sweating, severe dehydration, and hypotension.
- At-risk groups: very young, elderly, outdoor workers, those with chronic illnesses, and those on certain medications (CNS depressants, anticholinergics, diuretics, beta blockers).
- Management: remove from heat, cool externally (fans, cool compresses, air conditioning), give isotonic IV fluids (NS, LR), and monitor for seizures and AKI.
- Prevent with hydration (prefer electrolyte solutions over water), limit heat exposure, and monitor at-risk populations.
Malignant Hyperthermia
- Rare, inherited muscle disorder triggered by certain anesthetic agents (halothane, enflurane, isoflurane, succinylcholine).
- Characterized by sustained muscle contraction, hyperthermia (>111°F), rapid CO₂ rise, and tachycardia.
- Early sign: tachycardia, unexplained drop in O₂, rise in end-tidal CO₂.
- Complications: rhabdomyolysis, hyperkalemia, AKI, cardiac arrest.
- Management: immediate dantrolene sodium administration, cooling (external and internal), treat hyperkalemia, monitor kidney function.
- Prevention: thorough pre-op assessment for personal/family history of anesthesia reactions.
Cold-Related Emergencies
Frostbite
- At-risk: homeless, mentally ill, elderly, outdoor workers, athletes.
- Most affected areas: nose, ears, fingers, toes, cheeks.
- Degrees: frostnip (redness, pain), mild to severe frostbite (possible blackened tissue).
- Prevention: wear layers, moisture-wicking materials (avoid cotton), only one layer of socks.
- Management: remove from cold, take off wet clothing, rapid rewarming (98.6–104°F water), give analgesics, avoid refreezing, protect rewarmed areas.
Hypothermia
- At-risk: elderly, infants, chronically ill, homeless, those with decreased mobility.
- Management: remove wet clothing, use dry and warm materials, prioritize warming the core (trunk) before extremities, utilize forced air warming blankets (e.g., Bear Hugger).
- In cardiac arrest, extend resuscitation efforts since hypothermia preserves organ function ("not dead until warm and dead").
- Internal and external warming methods (warm IV fluids, lavage stomach/rectum/bladder with warm fluids).
Key Terms & Definitions
- Heat Exhaustion — Dehydration and salt loss due to prolonged heat exposure, reversible with cooling and hydration.
- Heat Stroke — Life-threatening failure of thermoregulation with elevated core temperature (>104°F) and altered mental status.
- Malignant Hyperthermia — Acute reaction to certain anesthesia drugs causing uncontrolled muscle contractions and extreme fever.
- Frostbite — Tissue damage from freezing temperatures, ranges from superficial (frostnip) to deep (necrosis).
- Hypothermia — Core body temperature below 95°F, leading to slowed metabolism and potential cardiac arrest.
- Rhabdomyolysis — Muscle breakdown releasing myoglobin, leading to kidney damage.
- Anhidrosis — Absence of sweating.
Action Items / Next Steps
- Read chart 67-6 on prevention of heat stroke/exhaustion.
- Review medications and chronic conditions that affect thermoregulation.
- Memorize emergency management steps for heat and cold related injuries.
- Study the protocol for malignant hyperthermia and contents of the emergency kit.