Overview
Definition:
Heat stroke is a life-threatening medical emergency characterized by a severely elevated body core temperature (typically >40°C or 104°F) accompanied by central nervous system dysfunction, resulting from a failure of thermoregulation.
Epidemiology:
In adolescents, heat stroke is often exertional, occurring during strenuous physical activity in hot and humid environments
Factors like dehydration, lack of acclimatization, certain medications, and underlying health conditions increase risk
Incidence peaks during summer months and in athletic populations.
Clinical Significance:
Heat stroke carries a high morbidity and mortality if not recognized and treated promptly
Rapid and effective cooling is paramount to prevent multi-organ failure, neurological damage, and death, making it a critical topic for pediatric residents preparing for DNB and NEET SS examinations.
Clinical Presentation
Symptoms:
Sudden onset of headache
Dizziness or lightheadedness
Nausea and vomiting
Muscle cramps or weakness
Altered mental status: confusion, disorientation, agitation, lethargy, coma
Absence of sweating (in classic, non-exertional heat stroke) or continued sweating (in exertional heat stroke).
Signs:
Core body temperature >40°C (104°F)
Tachycardia and tachypnea
Hypotension
Hot, dry skin (less reliable in exertional cases)
Neurological deficits: delirium, seizures, coma
Rhabdomyolysis (muscle breakdown) indicated by dark urine
Rapid progression of symptoms is common.
Diagnostic Criteria:
Core body temperature >40°C (104°F) measured rectally or via other reliable core methods
Central nervous system dysfunction (e.g., behavioral changes, confusion, coma, seizures)
Absence of other explanations for the elevated temperature and CNS dysfunction
Typically, a history of exposure to heat stress or strenuous activity.
Diagnostic Approach
History Taking:
Nature of activity and duration
Environmental conditions (temperature, humidity)
Fluid intake and type
Any recent illness or fever
Medications (diuretics, anticholinergics, psychostimulants)
Previous heat illness episodes
Underlying medical conditions (cardiac, renal, endocrine).
Physical Examination:
Vital signs: temperature, heart rate, blood pressure, respiratory rate
Neurological assessment: GCS, pupillary response, focal deficits
Skin assessment: hydration, color, presence of sweat
Assess for signs of rhabdomyolysis (muscle tenderness) and organ damage.
Investigations:
Complete blood count with differential (rule out infection, assess for hemolysis)
Electrolytes, BUN, creatinine (assess for dehydration, renal injury, electrolyte imbalances)
Liver function tests (assess for hepatic injury)
Creatine kinase (assess for rhabdomyolysis)
Arterial blood gas (assess acid-base status, oxygenation)
Urinalysis (hematuria, myoglobinuria)
Coagulation profile
ECG (arrhythmias)
Lactate levels.
Differential Diagnosis:
Meningitis or encephalitis (especially if fever > CNS signs)
Sepsis
Drug-induced hyperthermia (e.g., neuroleptic malignant syndrome, serotonin syndrome)
Malignant hyperthermia
Thyroid storm
Diabetic ketoacidosis
Heat exhaustion (less severe, without CNS dysfunction).
Management
Initial Management:
Immediate removal from heat source and cessation of exertion
Rapid cooling is the priority: immerse in ice-water bath or use evaporative cooling (wetting with water and fanning)
Monitor core temperature continuously
Establish IV access for fluid resuscitation and medications
ABCs assessment and management
Administer oxygen if hypoxemic.
Medical Management:
Intravenous fluid resuscitation: isotonic crystalloids (e.g., 0.9% normal saline) at a rapid rate (e.g., 20 mL/kg bolus, then titrated to hemodynamic response)
Monitor electrolytes closely and correct imbalances
Antipyretics (e.g., acetaminophen) are generally NOT effective and may be harmful if liver function is compromised
Benzodiazepines may be used cautiously to control shivering or agitation if it impedes cooling, but avoid oversedation.
Rapid Cooling Protocols:
Target core temperature is generally considered 38.5-39°C (101.3-102.2°F)
Immersion in ice-water bath: continuous immersion until target temperature is reached, with intermittent removal to monitor temperature and prevent hypothermia
Evaporative cooling: spray or sponge skin with cool water and use fans to maximize evaporation
Continuous monitoring of core temperature (rectal, esophageal, bladder, or pulmonary artery catheter) is crucial
Aggressively manage shivering, as it generates heat and hinders cooling
benzodiazepines may be used
Goal is rapid reduction of core temperature (aim for 1-2°C per 10 minutes initially).
Supportive Care:
Continuous cardiovascular and neurological monitoring
Aggressive management of rhabdomyolysis with aggressive IV hydration to prevent acute kidney injury
Monitor urine output
Treat seizures with benzodiazepines
Address coagulopathy if present
Consider cooling blankets and fans if immersion is not feasible or after reaching target temperature to prevent rewarming
Nutritional support is secondary to immediate resuscitation and cooling.
Complications
Early Complications:
Multi-organ dysfunction syndrome (MODS) including acute kidney injury (AKI), acute respiratory distress syndrome (ARDS), disseminated intravascular coagulation (DIC), hepatic dysfunction
Cerebral edema
Seizures
Cardiac arrhythmias
Rhabdomyolysis leading to renal failure
Hypoglycemia.
Late Complications:
Neurological sequelae: cognitive deficits, memory impairment, personality changes, persistent focal neurological deficits
Chronic kidney disease
Liver dysfunction.
Prevention Strategies:
Education on heat illness prevention for athletes, coaches, and parents
Gradual acclimatization to heat and exertion
Adequate hydration before, during, and after activity
Appropriate clothing
Recognition and management of early symptoms of heat exhaustion
Scheduled rest periods during intense exercise
Avoidance of strenuous activity during peak heat and humidity.
Prognosis
Factors Affecting Prognosis:
Time to initiation of cooling
Core body temperature at presentation
Presence and severity of CNS dysfunction
Development of multi-organ failure
Age and underlying health status.
Outcomes:
With prompt and aggressive cooling and supportive care, mortality can be significantly reduced
However, survivors may experience long-term neurological and physiological deficits
A rapid decrease in core temperature is associated with a better prognosis.
Follow Up:
Close monitoring for residual neurological deficits, renal function, and cardiac status
Rehabilitation services may be required
Long-term follow-up is essential to assess and manage chronic sequelae
Education on preventing recurrence is crucial.
Key Points
Exam Focus:
Heat stroke definition (>40°C + CNS dysfunction)
Rapid cooling is the FIRST and MOST IMPORTANT intervention
Ice water immersion is gold standard
Differentiate exertional vs
non-exertional heat stroke
Avoid antipyretics
Monitor core temperature continuously.
Clinical Pearls:
Think heat stroke in any adolescent with altered mental status in hot weather, especially after physical exertion
Don't be fooled by normal or even cool, dry skin in exertional heat stroke
Aggressively manage shivering to maximize cooling efficiency
Early aggressive fluid resuscitation is vital, but cooling is paramount.
Common Mistakes:
Delaying cooling measures
Relying on peripheral temperature measurements
Administering antipyretics like aspirin or paracetamol without considering organ function
Inadequate fluid resuscitation
Over-sedation with benzodiazepines leading to reduced cooling effectiveness
Not considering heat stroke in the differential for altered mental status in hot weather.