20.1 Environmental Emergencies
Key Takeaways
- Intramuscular epinephrine 0.3–0.5 mg of 1:1,000 in the anterolateral thigh is first-line anaphylaxis care; antihistamines do not replace it.
- Heat stroke is central-nervous-system failure; cool now with ice-water or ice packs, use benzodiazepines for shivering, and skip antipyretics.
- Handle hypothermia gently because the cold myocardium is irritable; afterdrop continues after rescue, and wet clothes come off before the cabin hop.
- Do not thaw frostbite if refreeze is likely; freeze–thaw–refreeze destroys more tissue than a delayed hospital thaw.
- Submersion is a hypoxia disease: ventilate, rewarm, and restrict the spine only when the mechanism supports it. Crotalid care is immobilize, mark, and antivenom destination — no ice, cut, or suck.
Domain 4.H of the August 2026 Board of Certification for Emergency Nursing (BCEN) Certified Flight Registered Nurse (CFRN) outline tests Environment as allergic reactions, temperature-related injury, submersion, and bites and envenomation. Toxicology is section 20.2. Evolved-gas disorders such as decompression sickness (DCS) and high-altitude pulmonary edema (HAPE) sat on the outgoing outline; they are not a 2026 Domain 4.H lecture.
Anaphylaxis
First-line epinephrine and the airway
Treat anaphylaxis as a distributive-shock airway emergency, not a rash. The first drug is intramuscular (IM) epinephrine 0.3–0.5 mg of 1:1,000 (1 milligram per milliliter) in the anterolateral thigh. Repeat every 5 to 15 minutes if blood pressure or work of breathing is still wrong. Do not hide the first dose in a deltoid subcutaneous trickle, and do not wait for an intravenous (IV) line.
Give large-bore IV crystalloid. Capillaries leak; the tank is empty. Keep a second epinephrine infusion plan ready if IM doses fail. Histamine-1 (H1) and histamine-2 (H2) antihistamines and corticosteroids do not reverse obstruction or hypotension. They do not replace epinephrine.
Watch the airway. Voice change, stridor, tongue swelling, and persistent wheeze mean the airway will not last the hop. Intubate on the ground while you can still pass a tube. Biphasic anaphylaxis can return hours after the first wave looks finished. A "fine now" patient still needs a monitored receiving bed, not a ride home.
Hymenoptera stings (bees, wasps, hornets, fire ants) are an anaphylaxis pathway on this outline. Scrape a visible stinger. Do not squeeze the sac.
Heat exhaustion versus heat stroke
Cooling is the flight intervention. Antipyretics reset a hypothalamic set point. Environmental hyperthermia is not a fever.
| Feature | Heat exhaustion | Heat stroke |
|---|---|---|
| Core temperature | Often under 40°C | Usually 40°C or higher |
| Mentation | Fatigue, dizziness, still interactive | Confusion, seizure, coma — central nervous system (CNS) failure is the definition |
| Skin | Sweaty, cool or clammy | Classic (older, dry, hot) or exertional (still sweaty) |
| Immediate action | Shade, oral or IV fluid, stop work | Cool now, then move |
Cool now
Ice-water immersion is the most effective field method for exertional heat stroke. If you cannot immerse, pack ice to the groin, axillae, and neck and use wet sheets plus fanning. Rotor wash on the pad helps evaporation; it does not replace ice after the doors close. Benzodiazepines treat shivering and seizures; shivering generates heat. Do not give acetaminophen or ibuprofen. Keep cooling in the cabin. Space the patient so ice packs stay in contact.
Hypothermia
Use a staged picture, not a single number.
| Stage (Swiss / common EMS) | Approximate core temperature | Clinical picture |
|---|---|---|
| Mild (HT I) | 32–35°C | Conscious, shivering |
| Moderate (HT II) | 28–32°C | Impaired consciousness, shivering fades |
| Severe (HT III) | 24–28°C | Unconscious, vital signs present |
| Apparent death (HT IV) | under 24°C | No vital signs — "not dead until warm and dead" in the right context |
Afterdrop and an irritable myocardium
Afterdrop is continued core cooling after you leave the cold, when cold peripheral blood returns to the core. Handle gently. The cold myocardium is irritable. Rough log-rolls, sudden upright sitting, and extra stimulation can trigger ventricular fibrillation (VF). Below about 30°C, shocks and drugs may fail until the patient is warmer. Remove wet clothes. Package horizontal. Combine passive insulation with active external rewarming (warm blankets, chemical packs to the trunk, cabin heat).
Frostbite
Frostbite is frozen tissue. Superficial looks white and still pliable. Deep is hard, woody, and anesthetic. Do not rub snow on it. Do not thaw in the cabin if refreeze is likely — a weather divert, a long scene, or an unheated pad. Freeze–thaw–refreeze destroys more tissue than a delayed hospital thaw. Protect the part. Separate digits with dry gauze.
Submersion
Hypoxia is the disease, not the water in the lungs. Ventilate and oxygenate. There is no role for the Heimlich maneuver to "empty" water. Apply spinal motion restriction only when the mechanism supports it (dive into shallow water, boat strike, fall from a height). Cold water can look like death; rewarm and ventilate while you decide. After the airway is secured, a drowned lung may need positive end-expiratory pressure (PEEP) and fraction of inspired oxygen (FiO2) of 1.0. Remove wet clothes so the cabin does not finish the hypothermia curve.
Bites and envenomation
Crotalid (pit viper: rattlesnake, copperhead, cottonmouth) venom is local tissue injury plus coagulopathy. Immobilize the limb in a functional position near heart level. Mark the leading edge of swelling with time. Fly to an antivenom-capable receiving hospital (Crotalidae polyvalent immune Fab / CroFab or an equivalent product). Rings come off before the hand swells shut.
- Do not ice the bite.
- Do not cut or suck the wound.
- Do not apply an arterial tourniquet.
- Do not invent a field fasciotomy.
Black widow (Latrodectus) is neurotoxic cramp, rigidity, and hypertension. Brown recluse (Loxosceles) is a delayed cytotoxic dermonecrotic lesion. Support, pain control, and destination—not field antivenom.
Cabin package
Continue the thermal plan you started on the ground.
- Keep cooling a heat-stroke patient; keep insulating and gently rewarming a cold one.
- Strip wet clothes.
- Give ice packs or warm packs space so they stay on the trunk.
- Leave room to reassess the anaphylaxis airway and the crotalid leading edge in flight.
A construction worker is stung by a wasp. He is wheezing, hypotensive at 78/40 mm Hg, and his lips are swelling on the landing zone. What is the first-line flight intervention?
A football player is unresponsive after a late-summer practice. Rectal temperature is 41.2°C. He still has some sweat and is not shivering. What is the correct flight package?
A boater is pulled from cold water after a collision. He is apneic and bradycardic. His fingers are white and hard. The receiving pad is 80 minutes away over a pass that may force a weather divert. What is the correct package?