What is the definition of heat stroke (Hyperthermia)?

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Last updated: April 4, 2025View editorial policy

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From the Guidelines

Heat stroke is defined as a core body temperature rising to more than 40°C and central nervous system abnormalities such as delirium, convulsions, and/or coma resulting from exposure to a high environmental temperature or strenuous physical exercise. This definition is based on the most recent and highest quality study available, which emphasizes the importance of rapid cooling and hemodynamic management in heatstroke treatment 1. The condition typically develops when exposure to high temperatures overwhelms the body's cooling mechanisms, causing body temperature to rise dangerously. Heat stroke presents with symptoms including altered mental status (confusion, agitation, seizures, or coma), hot and dry or sweaty skin, rapid heartbeat, rapid breathing, headache, and sometimes nausea or vomiting. There are two main types: classic heat stroke, which develops slowly over days of heat exposure and affects primarily elderly or chronically ill individuals, and exertional heat stroke, which occurs suddenly during intense physical activity in hot conditions.

Some key points to consider in the diagnosis and treatment of heat stroke include:

  • The importance of measuring core body temperature, with rectal thermometry being the most accurate method 1
  • The need for rapid cooling, with whole-body immersion in cold water being the most effective method 1
  • The importance of immediate medical attention, as heat stroke can cause organ damage or failure if not promptly addressed 1
  • The role of prevention, including staying hydrated, avoiding outdoor activities during peak heat hours, wearing lightweight clothing, and acclimatizing gradually to hot environments 1

Overall, heat stroke is a severe and potentially life-threatening condition that requires prompt recognition and treatment to prevent morbidity and mortality. Immediate treatment with rapid cooling and medical attention is crucial to improve outcomes in patients with heat stroke.

From the Research

Definition of Heat Stroke

  • Heat stroke is a serious and potentially life-threatening condition defined as a core body temperature >40.6 degrees C 2.
  • It is clinically diagnosed as a severe elevation in body temperature with central nervous system dysfunction that often includes combativeness, delirium, seizures, and coma 3.
  • The diagnosis of heatstroke should be considered in any hyperthermic patient with altered mental status during a heat wave or following vigorous muscle exertion 4.

Forms of Heat Stroke

  • Two forms of heat stroke are recognized: classic heat stroke and exertional heat stroke 2.
  • Classic heat stroke primarily occurs in immunocompromised individuals during annual heat waves, while exertional heat stroke is observed in young fit individuals performing strenuous physical activity in hot or temperature environments 3.

Clinical Manifestations and Complications

  • Associated clinical manifestations of heat stroke include extreme fatigue, hot dry skin or heavy perspiration, nausea, vomiting, diarrhea, disorientation, dizziness, uncoordinated movements, and reddened face 2.
  • Potential complications related to severe heat stroke are acute renal failure, disseminated intravascular coagulation, rhabdomyolysis, acute respiratory distress syndrome, acid-base disorders, and electrolyte disturbances 2.
  • Long-term neurologic sequelae, including varying degrees of irreversible brain injury, occur in approximately 20% of patients 2.

Risk Factors and Management

  • Risk factors for heat stroke include environmental factors, medications, drug use, compromised health status, and genetic conditions 3.
  • Management of heat stroke should be carried out decisively and expeditiously, with cooling measures, fluid resuscitation, and electrolyte replacement beginning promptly to optimize prognosis 2, 4.

References

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Research

Heat stroke: a comprehensive review.

AACN clinical issues, 2004

Research

Heat stroke.

Comprehensive Physiology, 2015

Research

Heatstroke.

Handbook of clinical neurology, 2018

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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