Thursday, June 3, 2021

Heat-related illnesses case file

Posted By: Medical Group - 6/03/2021 Post Author : Medical Group Post Date : Thursday, June 3, 2021 Post Time : 6/03/2021
Heat-related illnesses case file
Eugene C. Toy, MD, Barry C. Simon, MD, Terrence H. Liu, MD, MHP, Katrin Y. Takenaka, MD, Adam J. Rosh, MD, MS

Case 45
A 74-year-old man is found in his small apartment after having a seizure on a hot summer day. The paramedics state they found him in a poorly ventilated apartment without any air conditioning. They established an IV of normal saline prior to arrival and obtained a fingerstick glucose of 146 mg/dL. Because he was postictal during transport, they were unable to obtain any other history about past medical problems, medications, or allergies.

On arrival in the emergency department (ED), his temperature is 41.1°C (106°F), blood pressure is 157/92 mm Hg, heart rate is 156 beats per minute, and respiratory rate is 28 breaths per minute. He is extremely warm to touch. He is combative, moaning, and flailing his arms and legs at staff. His pupils are midrange and reactive to light. His mucous membranes are dry. His neck is supple. His skin is flushed, hot, and dry.

 What is the most likely diagnosis?
 What is the best initial treatment?

Heat-Related Illnesses

Summary: This is a 74-year-old man with a seizure who is hyperthermic, tachycardic, tachypneic, and altered mental status.
  • Most likely diagnosis: Seizure secondary to heat stroke, but is essential to rule out other causes such as sepsis and medications overdose.
  • Best initial treatment: Management of the ABCs and rapid cooling

  1. Learn the clinical signs and symptoms associated with heat-related illness.
  2. Learn the management and treatment of heat-related illness.

When evaluating hyperthermic patients, the clinician must first determine if the patient has a fever or suffering from heat stroke. The presumptive diagnosis of heat stroke can be made on the basis of environmental conditions and circumstantial evidence (hot day, enclosed apartment without air conditioning or adequate ventilation), and the next step is to determine the severity of the patient’s heat-related illness, which could be useful in guiding his treatment. Because heat stroke has a mortality of 10% to 20% even with treatment, it is essential to diagnose and begin therapy immediately. This patient has severe heatstroke, as evidenced by his altered mental status and seizure. Simultaneously, laboratory and radiographic studies should be performed to rule-out infectious etiologies and drug overdoses.

Approach To:
Heat-Related Illnesses

HEAT STRESS: Feeling of discomfort and physiologic strain with normal core temperatures. These patients exhibit decreased exercise tolerance and no other symptoms.

HEAT EXHAUSTION: Mild dehydration, with or without sodium abnormalities. Patients have profuse sweating, thirst, nausea, vomiting, confusion and headache, and may have collapsed. Core temperatures range from 38°C to 40°C (100°F-104°F). Generally, the victim is not able to continue his/her activities as the result of the environmental conditions.

HEAT STROKE: Severe dehydration with core temperature greater than 40°C. Patients are flushed, with hot, dry skin. Symptoms include those associated with CNS disturbances such as dizziness, vertigo, syncope, confusion, delirium, and unconsciousness. Classically, heat strokes develop slowly over days and occur more frequently in older individuals with chronic illnesses.

EXERTIONAL HEAT STROKE: Heat stroke affecting individuals involved in strenuous physical activities. This type of heat stroke can have a more rapid onset than non-exertional heat strokes. Weather conditions including high humidity and increased temperatures are risk factors. The at-risk individuals are highly motivated athletes, laborers, and soldiers.

The primary abnormality in heat-related illnesses is the individual’s inability to adequately transfer heat (produced from normal metabolic activities) to the environment resulting in an increase in core temperature. Risk factors for developing heat illness include ambient heat and humidity, extremes of age, strenuous exercise, cardiovascular disease, dehydration, obesity, impaired mentation, and various medications (eg, diuretics, anticholinergics, antihistamines, phenothiazines, cyclic antidepressants, sympathomimetics, alcohol).

The spectrum of heat-related illness varies in severity from benign to severe. Table 45–1 describes the minor syndromes. In contrast to these benign entities, heat stroke is characterized by a loss of thermoregulation, tissue damage, and multiorgan failure. Classically, patients present with hyperpyrexia (temperature >41°C [106°F]), central nervous system (CNS) dysfunction (eg, altered mental status, seizure, focal neurological deficits), and anhidrosis.

Diagnosing heat stroke is largely a matter of ruling out other causes of hyperthermia with concomitant CNS dysfunction. The differential includes alcohol withdrawal; salicylate toxicity; phencyclidine, cocaine, and amphetamine toxicity; tetanus; sepsis; neuroleptic malignant syndrome; encephalitis, meningitis, and brain abscess; malaria; typhoid fever; malignant hyperthermia; anticholinergic toxicity; status epilepticus; cerebral hemorrhage; diabetic ketoacidosis; and thyroid storm.

Laboratory studies should include complete blood count, electrolytes, blood urea nitrogen (BUN)/creatinine, glucose, liver enzymes, coagulation studies, urinalysis, urine myoglobin, and arterial blood gas. An electrocardiogram (ECG) should be considered if the patient has syncope or a history of cardiovascular disease. Chest radiographs are useful to rule out aspiration or any pulmonary infection. CT scan of the head and/or lumbar puncture may also be needed.

In treating heat stroke, the clinician should strive to stabilize the ABCs, commence rapid cooling, replace fluid and electrolyte losses, and treat any complications. The goal is to cool the patient to 40°C (104°F) to avoid overshoot hypothermia. There are a number of cooling methods that are applied and these can be divided

minor heat illnesses

categorically as evaporative techniques and conduction techniques. Although there are strong proponents for the different cooling methods, there is no current consensus regarding which of the techniques is most effective. In all patients, the initial measures consist of removing the patient from the hot environment if possible and removing clothing. Evaporative cooling using cool mist and fans is simple and effective approach to cooling in the field; the evaporative approach is advocated by a number of investigators because the physical cooling principle suggests that the evaporation of 1 ml of water is associated with seven times the amount of heat dissipation when compared to melting 1 g of ice. Alternative cooling methods also include ice packs to the groin and axillae, cooling blankets, ice water immersion, peritoneal lavage, and cardiopulmonary bypass. Antipyretics are not effective in this scenario.

In addition, shivering can be controlled with benzodiazepines or phenothiazines. Benzodiazepines can also be used to treat any seizures. If the laboratory studies reveal evidence of rhabdomyolysis, mannitol and alkalinization of the urine are other considerations. The most common complications of heat stroke are rhabdomyolysis, renal failure, liver failure, disseminated intravascular coagulation, heart failure, pulmonary edema, and cardiovascular collapse.

The following independent negative prognosticators for survival have been identified, and these include age >80 years, cardiac disease, cancer, core temperature >40°C, living in an institutions, previous diuretic use, systolic BP <100 mm Hg, GCS <12, and transport to hospital by ambulance.


45.1 A 33-year-old man is found comatose at a construction site in the noon-hour on a hot summer day. His core temperature is 41.7°C (107°F). The ED physician orders evaporative cooling measures and ice packs. The patient begins with intense shivering. Which of the following is the best next step?
A. Continued observation.
B. Short-acting benzodiazepine.
C. Begin intravenous cooling solution.
D. Increase the number of ice bags.
E. Stop the cooling.

45.2 A 70-year-old man is brought into the ED complaining of headache and fatigue. His blood pressure is 100/70 mm Hg, heart rate is 100 beats per minute, and core temperature is 40.3°C (104.5°F). Upon using ice bags, his core temperature is down to 38°C (100.4°F). Which of the following is the best next step?
A. Observation for 4 to 6 hours and then, if stable, discharge home.
B. Continue ice bags until the core temperature is 36.7°C (98°F).
C. Admission to the hospital for observation of complications.
D. Administer cold gastric lavage.
E. Discharge the patient only if he can be placed in a different environment after discharge.


45.1 B. This patient most likely has exertional heatstroke where core temperature elevations may occur rapidly; therefore, measurement directed at reducing his core temperature are appropriate and must be continued. Benzodiazepines are first-line therapy for shivering or seizures in heat stroke.

45.2 C. All patients with severe heat exhaustion or heat stroke, particularly those who are older, should be admitted.

 Heat stroke is distinguished from other heat illnesses by a loss of thermoregulation, tissue damage, and multiorgan failure. Classically, these patients present with hyperpyrexia and CNS dysfunction.

 Because heat stroke has a mortality of 10% to 20% even with treatment, it is essential to diagnose and begin therapy immediately.

 The treatment of heat stroke consists of stabilizing the ABCs, rapid cooling, replacing fluid and electrolyte losses, and treating any complications (eg, shivering, seizures, rhabdomyolysis).


Becker JA, Stewart LK. Heat-related illness. Am Fam Physician. 2011;83:1325-1330. 

Hadad E, Rav-Acha M, Heled Y, Epstein Y, Moran DS. Heat stroke: a review of cooling methods. Sports Med. 2004;34:501-511. 

Hausfater P, Megarbane B, Dautheville S, et al. Prognostic factors in non-exertional heatstroke. Intensive Car Med. 2010;36:272-280.


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