Environmental Emergencies: Heat, Cold, Bites and Diving

Mechanisms of Heat Transfer and Heat-Related Emergencies

The human body constantly exchanges thermal energy with its surroundings through five distinct physical processes. Conduction is the transfer of body heat to another object through direct physical contact, such as lying directly on cool ground. Convection occurs when body heat is lost or gained through the movement of surrounding air or water currents across the skin, much like a breeze blowing across an overheated person. Radiation involves the direct transfer of heat from the body surface into the surrounding environment without any physical contact. Evaporation cools the body when liquid perspiration or moisture changes into water vapor on the surface of the skin. Finally, respiration causes heat loss when warm, humidified air is exhaled from the lungs and cooler environmental air is inhaled.

When environmental conditions or intense exertion overwhelm these heat-regulating mechanisms, hyperthermic conditions can emerge along a spectrum of severity. Heat cramps are a heat-related illness marked by painful, involuntary muscle spasms during or after exertion; they do not necessarily precede heat exhaustion or heat stroke. These spasms are often associated with heavy sweating along with fluid and salt loss. The initial care provided by an EMT includes moving the patient to a cool environment and allowing the affected muscles to rest. Heat exhaustion may cause moist, pale or flushed skin, dizziness, weakness, nausea, and a normal or elevated body temperature. Crucially, patients experiencing heat exhaustion do not display the altered mental status that defines more critical heat illness. EMT management for heat exhaustion involves moving the patient to a cool environment, positioning them for comfort, removing excess clothing, and cooling the patient with damp towels and fanning.

Heat stroke is a severe, life-threatening emergency defined by core hyperthermia accompanied by altered mental status. While many people believe dry skin is required for this diagnosis, patients suffering from heat stroke may present with either hot, flushed, dry skin or profuse sweating. Altered mental status is the primary clinical finding that differentiates heat stroke from heat exhaustion. When evaluating hydration status in any heat-related emergency, oral fluids must never be given to a patient who has an altered mental status, is vomiting, or cannot swallow safely. Small sips of oral fluids may only be offered to an alert patient who can tolerate them, provided this is permitted under local protocol.

Active, rapid cooling must be initiated immediately for any patient exhibiting signs of heat stroke. Cold-water immersion up to the neck is the most effective and rapid method for cooling patients suffering from exertional heat stroke. If whole-body cold-water immersion is unavailable, the EMT must rapidly cool the patient using water and fanning, while applying ice packs to the neck, axillae, and groin as available under local protocol. It is critical that the EMT does not stop rapid cooling solely because the patient begins to shiver or because their mental status begins to improve. Continuous monitoring is essential, and prehospital providers must strictly adhere to local protocol regarding when to discontinue active cooling.