Heat illness, hypothermia and environmental emergencies — branching viva

Opening (candidate)

I have two time-critical resuscitations running in parallel. The runner has exertional heat stroke — a core above forty degrees with central nervous system dysfunction — and my priority is to remove the heat and cool him immediately by cold-water immersion to a core below thirty-nine degrees within thirty minutes, because the duration above forty degrees is the chief determinant of survival; I will not wait for investigations or give antipyretics, which do not work in heat stroke. The 7-year-old is profoundly hypothermic at twenty-seven degrees and now in ventricular fibrillation; I continue cardiopulmonary resuscitation, deliver a single shock, withhold further shocks and adrenaline until the core is above thirty degrees, rewar actively, and escalate to extracorporeal rewarming — because nobody is dead until warm and dead. [1] [3] [7]

Branch A — The runner: rapid cooling

Examiner: The runner is sweating profusely. Are you sure this is heat stroke, and what is your cooling target? [3]

Candidate: Yes — heat stroke is defined by a core over forty degrees with central nervous system dysfunction, and this athlete is confused and combative at 41.5 degrees, which is heat stroke. The profuse sweating does not exclude it, because exertional heat stroke often presents with sweating preserved; the hot, dry skin is typical of classic non-exertional heat stroke, not this athlete. My cooling target, from the National Athletic Trainers' Association position statement, is a core below thirty-nine degrees within thirty minutes, using cold-water immersion which cools at roughly 0.15 degrees per minute and gives near-complete survival. I remove his clothing, secure the airway, give oxygen and intravenous access, and begin cold-water immersion now — cool first and transport second. [3]

Branch B — Drugs that do not work

Examiner: A colleague suggests intravenous paracetamol and dantrolene. Walk me through your reasoning. [1]

Candidate: I would not give either. In fever the hypothalamus resets its set point upward and antipyretics lower it, but in heat stroke the set point is normal and the body is overwhelmed by an external heat load, so paracetamol and non-steroidal anti-inflammatory drugs do not lower the temperature — and paracetamol may compound the liver injury that heat stroke already causes. Dantrolene, the specific therapy for malignant hyperthermia, has not been shown to improve outcome in heat stroke. The definitive treatment is physical cooling, not pharmacology. The only drug-induced hyperthermia in which dantrolene works is malignant hyperthermia from a volatile anaesthetic or succinylcholine trigger, which this athlete does not have. [3]

Branch C — The cold child: staging and the arrest rules

Examiner: Switch to the 7-year-old. Stage him and give me your defibrillation and drug strategy. [5] [7]

Candidate: At twenty-seven degrees he is Swiss stage three — severe hypothermia, unconscious with vital signs — at the boundary of stage two and three, and the matching rewarming is active internal: warmed humidified oxygen at forty-two to forty-six degrees and warmed intravenous crystalloid at approximately forty degrees, with gentle handling. Now he is in ventricular fibrillation below thirty degrees, so I deliver a single shock at standard energy, and if it fails I withhold further shocks and adrenaline until the core rises above thirty degrees, continuing compressions and rewarming. Once above thirty degrees I resume standard shocks and adrenaline but lengthen the adrenaline interval because clearance is slowed. I continue resuscitation until the core reaches at least thirty-two degrees before considering termination, because nobody is dead until warm and dead, and I escalate to extracorporeal rewarming as early as the system allows. [3]

Branch D — Altitude on the history

Examiner: The runner's parents mention the family trekked to altitude last month, when the younger sibling had a headache and ataxia. How would you have managed that child? [8] [10]

Candidate: A headache plus one or more of gastrointestinal upset, fatigue or dizziness after recent ascent above two thousand five hundred metres is acute mountain sickness by the 2018 Lake Louise score — managed by stopping the ascent, resting, hydrating, analgesia, antiemetics, and acetazolamide, one hundred and twenty-five milligrams twice daily for an older child or two point five milligrams per kilogram every twelve hours paediatric. But ataxia is the danger sign that escalates the diagnosis to high-altitude cerebral oedema, and the definitive treatment is immediate descent, supplemented by dexamethasone eight milligrams then four every six hours and oxygen. Acetazolamide is added. Descent is the act; the drugs support but do not replace it, and ascending with symptoms is the lethal error. [3]

Branch E — Prevention and the public-health arm

Examiner: Returning to first principles — how do you prevent the next heat stroke in this community? [3]

Candidate: Prevention is the public-health core. For exertional heat illness I counsel gradual acclimatisation, hydration, scheduling exercise for the cooler hours, modifying or cancelling activity in extreme heat, and ensuring that cold-water immersion is available at events — because survival depends on the speed of cooling. For classic heat stroke and paediatric vehicular heatstroke the message is to protect the vulnerable: heatwave plans and cool shelters, checking on the elderly, and never leaving a child in a car, because the interior rises rapidly and a small child reaches a fatal core temperature within minutes. Community education and event policy are what stop the next child reaching my resuscitation bay. [3]

Close

Two parallel resuscitations, one principle each: cool the heat stroke immediately to below thirty-nine degrees within thirty minutes with cold-water immersion and no antipyretics, and resuscitate the cold child with one shock below thirty degrees, withheld drugs, active rewarming and extracorporeal escalation until the core is at least thirty-two degrees — because nobody is dead until warm and dead. Debrief both teams, document the time intervals, and speak honestly and early with both families about the prognostic uncertainty of the first days. [3] [7]