Heat Stroke: Symptoms, Investigations & Emergency Management | MBBS Notes for Interns
Heat stroke is the most severe form of heat-related illness and is a life-threatening medical emergency. It occurs when the body's thermoregulatory mechanisms fail, leading to a rapid rise in core body temperature and widespread cellular injury.
Heat stroke should be suspected in any patient who collapses during or after strenuous exercise, or in individuals exposed to extreme environmental heat, especially those belonging to high-risk groups.
A core body temperature above 41°C strongly supports the diagnosis, although patients may present with a lower recorded temperature if cooling has already begun before arrival at the emergency department.
Early recognition and rapid treatment are essential because prolonged hyperthermia can result in irreversible multi-organ damage and significant mortality.
Pathophysiology
Excessive elevation of body temperature causes direct cellular injury and triggers systemic inflammation. The extent of organ damage depends on both the peak temperature reached and the duration of hyperthermia.
Multiple organ systems may be affected:
Central Nervous System (CNS)
Heat stroke primarily affects the brain.
Possible consequences include :
• Cerebral oedema
• Petechial haemorrhages
• Focal neurological deficits
• Generalized neurological dysfunction
Neurological injury is responsible for many of the severe clinical manifestations and largely determines patient outcome.
Musculoskeletal System
Extensive skeletal muscle injury may occur, leading to rhabdomyolysis.
This results in the release of:
• Creatine kinase (CK)
• Myoglobin
• Potassium
• Urate
• Phosphate
These substances can contribute to acute kidney injury and metabolic disturbances.
Liver
Heat-induced hepatocellular injury causes elevation of liver enzymes.
Jaundice commonly develops approximately 24 hours after the initial event.
Kidneys
Acute renal failure may develop due to:
• Hypovolaemia
• Myoglobinuria
• Metabolic acidosis
• Disseminated intravascular coagulation (DIC)
Haematological System
Heat stroke may produce significant coagulation abnormalities including:
• Disseminated intravascular coagulation (DIC)
• Thrombocytopenia
• Leucocytosis
Metabolic Abnormalities
Common metabolic disturbances include:
• Hyperkalaemia or hypokalaemia
• Metabolic acidosis
• Respiratory alkalosis
• Hypoglycaemia
Clinical Features
Patients may continue to sweat despite severe heat stroke.
The skin may even feel relatively cool because peripheral vasoconstriction can reduce skin temperature despite marked hyperthermia.
Neurological Features
• ConfusionCardiovascular Features
• TachycardiaFeatures of Coagulopathy
• Purpura
Recommended Investigations
Management should begin immediately and must not be delayed while waiting for investigation results.
Useful investigations include:
• Arterial blood gas (ABG)
• Serum electrolytes and renal function
• Blood glucose measurement
• Creatine kinase (CK)
• Liver function tests (LFTs)
• Coagulation profile
• Serum urate
• Calcium
• Phosphate
• Electrocardiogram (ECG)
• Chest X-ray (CXR)
These investigations help assess the severity of organ involvement and guide ongoing management.
Emergency Management
1. Immediate Stabilization
Rapid intervention is critical.
Initial priorities include:
• Remove the patient from the hot environment.
• Remove excess clothing
• Assess and secure the airway.
• Endotracheal intubation and mechanical ventilation may be required in patients with impaired consciousness or respiratory failure.
• Administer high-concentration oxygen when indicated.
2. Rapid Cooling
Cooling should begin immediately.
Antipyretic medications such as paracetamol or aspirin are not effective because the elevated temperature results from failure of thermoregulation rather than hypothalamic fever.
Preferred Method
Evaporative cooling is generally considered one of the most effective techniques.
This involves:
• Spraying the exposed body with tepid water.
• Using fans to promote evaporation.
Additional measures may include:
• Ice packs applied to the neck, axillae, groin and scalp while avoiding prolonged direct contact.
• Advanced cooling techniques may be considered in specialised settings when conventional measures fail.
The target cooling rate is approximately 0.1°C per minute.
Active cooling should be discontinued once the core temperature falls below 39°C to reduce the risk of hypothermia.
3. Fluid Therapy
Fluid replacement should be guided by clinical assessment and haemodynamic status.
Patients with documented hypoglycaemia require prompt correction.
Persistent hypotension despite temperature reduction may require intravenous isotonic saline while carefully monitoring for fluid overload.
Invasive haemodynamic monitoring may be required in selected critically ill patients.
4. Urinary Monitoring
Insertion of a urinary catheter allows accurate monitoring of urine output.
If significant myoglobinuria develops, additional renal protective strategies may be considered according to institutional protocols.
5. Seizure Management
Seizures should be treated promptly using appropriate anticonvulsant therapy.
Respiratory depression should be anticipated following benzodiazepine administration, and airway support may be necessary.
Important Differential Diagnoses
Neuroleptic Malignant Syndrome (NMS)
NMS is an idiosyncratic reaction associated with antipsychotic medications, particularly:
• Haloperidol
• Chlorpromazine
• Thioridazine
Typical features include:
• Severe muscle rigidity
• Extrapyramidal signs
• Autonomic instability
• Dyskinesia
Management involves:
• Immediate discontinuation of the offending drug
• Active cooling
• Administration of dantrolene when indicated
Malignant Hyperthermia
Malignant hyperthermia is a rare inherited disorder triggered by:
• Succinylcholine (suxamethonium)
• Volatile anaesthetic agents
Dantrolene is the specific treatment because it inhibits calcium release from skeletal muscle.
Quick Revision
✅ Heat stroke is a medical emergency.
✅ Core temperature is usually greater than 41°C.
✅ CNS dysfunction is a hallmark feature.
✅ Begin rapid cooling immediately.
✅ Do not delay treatment while waiting for investigations.
✅ Antipyretic drugs are ineffective.
Key Examination Points
• Heat stroke differs from heat exhaustion by the presence of central nervous system dysfunction.Educational Disclaimer
This article is intended solely for educational purposes for MBBS students, interns, and healthcare learners. It should be used as a revision aid and not as a substitute for clinical judgment, institutional protocols, or current evidence-based guidelines. Patient management should always be individualized and supervised by qualified healthcare professionals in accordance with local policies and updated clinical recommendations.
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