Chapter 227: Hyperthermic Patient Management

INTRODUCTION

The evaluation and management of hyperthermia and heat stroke can be difficult and challenging in the Emergency Department (ED). Heat stroke is defined as a core body temperature equal to or greater than 40°C with associated central nervous system dysfunction.¹ Heat stroke is a multisystem insult. There are two types of heat stroke, the classic nonexertional heat stroke and the exertional heat stroke. Classic heat stroke affects individuals most often over 70 years of age with underlying chronic medical conditions that impair thermoregulation, prevent removal from a hot environment, interfere with access to hydration, or interfere with attempts at cooling.² Exertional heat stroke generally occurs in young healthy individuals who engage in heavy exercise during periods of high ambient temperature and humidity. Typical patients are athletes and military recruits in basic training.³ More than 300 people die of heat-related illness in the United States each year.^4,5 This can more than double in years with prolonged heat waves.⁶ Exertional heat illness is one of the leading causes of death in young athletes each year.^5,7 Heat stroke is an uncommon medical emergency. It is considered one of the most important of all the environmental illnesses because of its potential for high morbidity and mortality in large numbers.⁸ Major complications of heat stroke include seizures, adult respiratory distress syndrome (ARDS), acute renal failure, liver disease, rhabdomyolysis, disseminated intravascular coagulation, and death.⁹

The patient must be exposed adequately. Cooling must be initiated in the quickest and most efficient manner possible as stabilization is occurring. Rapid cooling is the most effective strategy for minimizing morbidity and mortality from heat stroke and should be initiated as soon as possible and within 30 minutes of presentation.¹⁰ The most effective means of cooling remains controversial. Few controlled studies are available to determine the best method for achieving rapid cooling of patients. The techniques rely upon prompt recognition of symptoms, immediate intervention in the prehospital setting, a complete diagnostic evaluation in the ED, and the continued care in the ED. Begin cooling the patient in the prehospital setting by removing the patient from the heat stress, removing any excess clothing, keeping the skin wet, and fanning the patient in transport.

Continuous core temperature monitoring with a rectal or esophageal probe is mandatory. Cooling measures should be stopped once a temperature of 38°C to 39°C has been achieved to reduce the risk of iatrogenic hypothermia.¹¹ Cooling must precede the investigation for the cause. Evaporation and convection are the simplest and most efficient means of cooling victims of heat stroke or heat exhaustion. Skin blood flow is preserved as compared with the use of ice because evaporation and convection are much more efficient modes of heat exchange.¹² Evaporation of 1 gm of water dissipates approximately seven times more heat than melting the same quantity of ice.⁴

The ...