45: Environmental Emergencies

HEAT EXPOSURE EMERGENCIES

GENERAL CONSIDERATIONS

Heat-related illnesses occur when the body’s ability to dissipate heat is overcome by endogenous and/or environmental heat burdens. As the core body temperature (CBT) rises, a continuum of disease occurs from mild cutaneous findings to coma and death. Mild heat disorders such as heat edema and heat cramps are sequelae of the body’s compensatory mechanisms to dissipate heat. Treatment principles are aimed primarily at supportive care for mild disease, and cooling plus hydration for more serious hyperthermic injuries. Children are at no increased risk due to anatomic or physiologic reasons compared with adults. However, infants and very young children can be at greater risk of heat-related illness in settings of abandonment, neglect, and inability to rehydrate.

The body uses four mechanisms to dissipate heat: radiation, conduction, convection, and evaporation. The body attempts to thermoregulate by two physiologic methods. Shunting of blood from core to dilated peripheral vessels allows conduction and convection, if ambient temperature and air movement allow for a heat gradient. Sweating allows for skin surface evaporation and is effective up to a relative humidity of about 75%. Very high temperatures, prolonged exposures, and high relative humidity can overwhelm the body’s heat dissipation efforts and lead to heat-related illness.

HEAT RASH (MILIARIA RUBRA)

Clinical Findings

Heat rash occurs when sweat saturates the skin, mixes with sebum and dead skin cells, and clogs the sweat ducts. It is characterized by a papulovesicular rash, which may be pruritic or mildly painful. Small pustules or vesicles may appear as the obstructed ducts continue to produce sweat, infiltrating the dermis and epidermis. Outbreaks usually occur in clothed areas where clothing traps the sweat against the skin, preventing sweat from evaporation or run off.

Treatment

Keeping the area cool and dry should provide resolution within a week. Lotions such as calamine and topical corticosteroids may provide symptomatic relief if the rash is uncomfortable. Rarely, staphylococcal or streptococcal superinfection may result from the vesicular rash. Secondary infections should be treated with appropriate topical or oral antibiotics.

Disposition

In the absence of severe cellulitis or rapidly spreading infection, patients with heat rash may be discharged home. Precautions should be given to parents regarding signs of spreading infection.

HEAT EDEMA

Clinical Findings

Heat edema is more typical in older persons but can occur in children. It is a benign bilateral swelling of the (typically lower) extremities due to peripheral vasodilation. It is seen almost exclusively in nonacclimatized individuals during the first few days of exposure to very hot conditions. The interstitial fluid will usually resolve spontaneously as acclimatization occurs.

Treatment

Compressive stockings and elevation of the ...