Exertional heat stroke — OSCE

Station brief (8–10 minutes)

A 15-year-old cross-country runner is carried into the emergency department after collapsing five kilometres into a race on a 39-degree summer afternoon. His rectal temperature is 41.5 degrees Celsius. He is confused and combative. His skin is hot and sweating profusely, his pulse is 140 beats per minute, his blood pressure is 104/60, and his capillary glucose is 6.2 mmol per litre. Cold-water immersion is available in the department. You are the registrar leading the resuscitation, with a skilled nurse and a junior doctor present. Recognise the diagnosis, lead the immediate cooling, state the drugs you would not give and why, and arrange the disposition. Name the source for each threshold and dose. [1] [3]

Tasks for the candidate

1. State the heat-stroke definition and justify the diagnosis in this athlete, explaining why the profuse sweating does not exclude it. [1]

2. Lead the immediate management with the cooling method, the cooling target and timeframe, and the airway, breathing, circulation and glucose steps. [3]

3. State which drugs you would not give (antipyretics, dantrolene) and the physiological reason, and distinguish heat stroke from malignant hyperthermia. [1]

4. Describe the investigations, the complications to anticipate, and the disposition. [2]

Key actions and talking points

• Diagnosis. Heat stroke is a core above forty degrees Celsius with central nervous system dysfunction; the mental state, not the sweat, is the pivot. This is exertional heat stroke (young athlete, exercise, sweating preserved). The hot, dry, anhidrotic picture is classic non-exertional heat stroke in the heatwave patient. [1] [4]
• Cooling. Remove from the heat and remove clothing; airway, oxygen, intravenous access; check the glucose (already normal). Begin cold-water immersion now — the gold standard for exertional heat stroke, cooling at roughly 0.15 degrees per minute. Target a core below thirty-nine degrees within thirty minutes — cool first and transport second. Where immersion is unavailable, use evaporative spray-and-fan, ice packs to neck, groin and axillae, cooled intravenous fluid, and cooling blankets. [3]
• Drugs to avoid. Do not give paracetamol, non-steroidal anti-inflammatory drugs or dantrolene. The hypothalamic set point is normal in heat stroke, so antipyretics do not lower the temperature, and paracetamol may compound the heat-stroke liver injury; dantrolene is the specific therapy for malignant hyperthermia, which this athlete does not have. Malignant hyperthermia is triggered by a volatile anaesthetic or succinylcholine, shows rigidity and hypercapnia, and responds to dantrolene. [1]
• Investigations. Creatine kinase for rhabdomyolysis, liver function tests for acute liver injury, coagulation for disseminated intravascular coagulation, urea, electrolytes and creatinine for acute kidney injury, glucose, blood gas, lactate, full blood count, and a septic and toxicology screen to separate sepsis and the drug-induced hyperthermias. These never delay cooling. [2]
• Disposition. Admit to a paediatric intensive care unit for multi-organ support, with fluid for rhabdomyolysis to protect the kidney, and monitoring for encephalopathy, acute kidney and liver injury, and coagulopathy. Early retrieval and intensive care liaison, and honest early family discussion of prognosis. [2]

Marking domains

• Patient safety and prioritisation. Recognises heat stroke from the core temperature and central nervous system dysfunction; begins cooling immediately and does not delay for investigations. [1] [3]
• Medical knowledge. Quotes the definition, the cold-water-immersion target of below thirty-nine degrees within thirty minutes, and the cool-first principle; explains why antipyretics and dantrolene are ineffective. [1] [3]
• Communication and team leadership. Allocates roles, names the thresholds and their source, and arranges retrieval and intensive care. [3]
• Differential reasoning. Separates exertional from classic heat stroke and distinguishes both from malignant hyperthermia, neuroleptic malignant syndrome, serotonin syndrome, sepsis and thyroid storm. [1] [2]
• Public health. Counsels on heatwave and exertional heat-illness prevention and on the cool-first event policy. [4]