Heat stroke for paramedics: why you cool first and transport second

#Two patients, one diagnosis

It's a hot July afternoon, the kind of day when every paramedic should have heat stroke on their mind. The first call is to a charity 10K, where a fit 24-year-old collapsed a few hundred metres from the finish. He's confused, combative, sweating and hot to the touch.

Two days later, in the same heat wave, the second call is a wellness check on an 81-year-old woman in a top-floor apartment with no air conditioning. She's drowsy, her skin is hot and dry, and nobody's seen her for a day.

Both patients may have heat stroke. They look very different, and the crew's instinct on each may be different too: with the runner, cool him down; with the older woman, get her to hospital. This breakdown covers why heat stroke for paramedics is fundamentally a cooling emergency, and why where you start cooling matters as much as how.

#What heat stroke is for paramedics

Heat stroke is a life-threatening rise in core body temperature with central nervous system dysfunction. That last part is the key clinical sign. Confusion, agitation, collapse, seizures or reduced level of consciousness in a hot environment should prompt you to think heat stroke until proven otherwise.

Guidelines commonly describe a core temperature above about 40°C alongside neurological changes. In the field, accurate core temperature is hard to get. Oral, tympanic and skin readings can badly underestimate it. So don't let a "normal-ish" peripheral reading talk you out of a diagnosis the clinical picture is making. Use whatever your service provides and follow your medical directives.

#Exertional versus classic heat stroke

The two forms share a final pathway but differ in who they affect and how they appear.

Exertional heat stroke

• Happens during intense activity: athletes, military recruits, outdoor workers, firefighters
• Often young and healthy patients
• Develops quickly, sometimes in under an hour
• Patients are often still sweating
• Usually witnessed, so time of onset is known

Classic heat stroke

• Develops over hours to days during heat waves
• Mostly older adults, people with chronic illness, those on medications affecting thermoregulation or hydration, and people who are socially isolated
• Patients may be dry, but not always
• Often found down, with an unknown time of onset
• Frequently complicated by dehydration, other illnesses and delayed discovery

Health Canada's guidance on extreme heat highlights the same at-risk groups for classic heat illness, which is useful context for dispatch and wellness-check calls during heat warnings.

#Why cooling on scene comes first

The damage from heat stroke depends on two things: how hot the body gets and how long it stays hot. Every minute at a dangerous temperature adds to the injury to the brain, kidneys, liver, muscles and clotting system.

That's the logic behind "cool first, transport second," a principle strongly emphasized in exertional heat stroke guidance such as the National Athletic Trainers' Association position statement. If transport takes time and the ambulance can't cool effectively en route, loading and driving means the patient stays hot for the whole trip.

The most effective method for exertional heat stroke is cold-water immersion, where available. Many sports events now have immersion tubs at the medical tent for exactly this reason. Where immersion isn't possible, practical options include:

• Ice-water-soaked towels rotated frequently over the whole body
• Ice packs to the neck, armpits and groin, as an adjunct rather than the main method
• Evaporative cooling with water spray and moving air
• Removing clothing and getting out of the heat as early as possible

Your service's medical directives will set which methods you can use, the targets for stopping active cooling and how to monitor. Overcooling is a real risk, so endpoints matter.

Cooling on scene isn't the same as delaying care. While cooling is under way, the rest of the assessment continues: airway, glucose, cardiac monitoring, IV access where your directives support it, and a clear pre-alert to the receiving hospital. Once cooling has clearly started and the patient is improving, or if your directives say to move, transport with cooling continued as best the vehicle allows.

#The decisions that delay cooling

Cooling delays usually come from reasonable-sounding thinking:

1. "Let's get going and cool in the truck." Ambulance cooling is often limited. Starting aggressive cooling on scene, then transporting, usually gets the temperature down faster.
2. Trusting a peripheral temperature. A modest tympanic reading in a confused patient after exertion isn't reassurance.
3. Anchoring on another diagnosis. Hypoglycemia, intoxication, head injury or a cardiac cause may coexist, but in a hot setting heat stroke needs to be on the list immediately.
4. Underestimating classic heat stroke. Older patients found at home often present quietly. Drowsiness in a hot apartment during a heat wave deserves the same urgency as a collapsed athlete.
5. Waiting for the "right" equipment. Cold water, towels and wet sheets are on most scenes. Start with what's there.

#For training leads

Heat stroke is seasonal, which makes it easy for crews to go a year without seeing it:

• Train in late spring, before the first heat warning.
• Run both versions: the obvious athlete and the quiet older adult found at home.
• Practise the cooling decision explicitly: should we cool here or go?
• Walk through your service's cooling equipment and directives, including endpoints.
• Coordinate with event medical teams in your area about immersion availability.

Scenario practice, on platforms like Imedica or in the station, helps make the "cool here first" decision automatic before summer arrives.

#The takeaway

Heat stroke is a race against time spent hot. Recognize it by altered mental status in a hot setting, don't trust peripheral temperatures to rule it out, and start aggressive active cooling on scene where your directives allow. Then transport. Exertional and classic heat stroke look different, but both need the same urgency.

Drafted for Imedica Field Notes. Physician review of this article is pending.