CHAPTER 63

( 104°F). Patients complain of nonspecific symptoms and

signs including weakness, dizziness, fatigue, nausea, vomiting,

headache, myalgias, tachycardia, tachypnea, hypotension, and

diaphoresis. By definition, mental status remains normal.

Heat stroke patients present with altered mental status (AMS)

ranging from mild confusion to coma. Body temperature is

elevated above 40°C ( 104°F), and they may or may not be

sweating. Patients can exhibit a wide range of neurologic

symptoms and signs, including ataxia, seizures, and hemiple -

gia. Multiorgan system failure consisting of hepatic, renal, and

cardiac impairment may also be present in severe cases .

..... History

Important factors to address in the history include a full

description of the circumstances surrounding the heat

exposure. Has the patient been in a non-air-conditioned

apartment in the summer for several days, or has the

patient been working outside while there is an elevated

heat index? Past medical history should include questioning

for medical conditions that increase the risk of heat illness

and medications that impede the body's ability to cool.

..... Physical Examination

Physical examination should involve complete exposure of

the patient to remove heat-trapping clothing and to assess

for any physical injuries.

DIAGNOSTIC STUDIES

..... Laboratory

A complete metabolic panel (CMP) should be drawn to

evaluate serum electrolytes. Hypo- or hypernatremia may be

present as well as hyperkalemia. Prerenal azotemia may also

be seen on the CMP, indicating impaired renal function. A

creatine phosphokinase should be checked to rule out rhabdomyolysis. As end-organ damage occurs, patients with heat

stroke may develop elevated liver enzymes (peaking at 24-72

hr), disseminated intravascular coagulopathy (DIC; thrombocytopenia, low fibrinogen levels, elevated fibrin split

products, elevated D-dimer), and coagulopathy (elevated

prothrombin time/partial thromboplastin time).

..... Imaging

A noncontrast computed tomography (CT) scan of the

brain should be performed on patients presenting with

AMS. In heat stroke, the CT is normal. Electrocardiogram

should be performed on all patients with heat exhaustion

and heat stroke to evaluate for signs of ischemia or electrolyte abnormalities.

MEDICAL DECISION MAKING

When a patient presents with a potential heat-related ill ­

ness, first priorities include airway, breathing, and circulation (ABCs) and vital signs with temperature (Figure 63-1).

Eliminating other causes for the patient's symptoms is also

important. Differential diagnosis should include meningitis, sepsis, thyroid storm, drug intoxication (PCP, amphetamines, cocaine), cerebral hemorrhage, and status

epilepticus. Neuroleptic malignant syndrome and sero ­

tonin syndrome should both be considered in any patient

taking psychiatric medications. Malignant hyperthermia,

although usually occurring in the context of inhalational

anesthetic or succinylcholine use, should be considered if

symptoms develop in a patient with a previous or family

history of this condition. Vigorous exercise may precipitate

this condition in susceptible individuals.

TREATMENT

Once other diagnoses are excluded, heat exhaustion is the

presumed diagnosis if the patient has normal mental status. Rehydration with either oral or intravenous (N) fluids

is appropriate. Consider oral volume replacement with an

electrolyte-containing solution if the symptoms are mild.

If there is any concern for potential complications from

comorbid conditions, N therapy and laboratory studies

should be instituted. In both cases, treat the patient with

ambient cooling, removal of heavy clothing, and rest .

After eliminating other potential differential diagnoses,

the diagnosis of heat stroke can be made when the patient

with suspected heat illness has an elevated temperature

(>40°C or 1 04°F) and AMS. Begin treatment immediately

with N volume and electrolyte replacement. Start with

250-500 mL of normal saline and replace other electrolytes

based on laboratory values. Be careful not to fluid-overload

older patients or those with cardiac problems .

Evaporative cooling should begin as soon as all life threats

have been assessed and ABCs are secure. Completely expose

the patient and mist with tepid water while a fan is blowing on

him or her. Specially made cool mist fans are highly effective,

but not available in most facilities. Alternatively, a spray bottle

and a box fan are sufficient to lower the patient's temperature.

The patient's core body temperature must be monitored fre ­

quently. A Foley catheter device that provides continuous

temperature evaluation or rectal temperatures recorded every

10 minutes is ideal. Patients may shiver during c ooling, which

is counterproductive by producing heat. Treat shivering with

low-dose benzodiazepines (lorazepaml mg N). When the

patient's temperature reaches 40°C or 104°F, all active cooling

measures should be discontinued. Continuing at lower t emperature can cause overshoot hypothermia. Search for complications from heat stroke such as cardiac ischemia, hepatic

and renal failure,