Compare conditions

Put any two — or three — conditions side by side, adult or pediatric, to spot the look-alike differences fast, row by row.

Heat Stroke

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In one line

·Body temperature climbs above 104°F (40°C) and the brain stops working right — cooling within minutes can save the person's life.

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Normal physiology

·The hypothalamus (a pea-sized control center deep in the middle of the brain) acts as the body's thermostat. It constantly reads the temperature of blood flowing past it and sends out orders to keep core temperature at 98.6°F. When you get hot, it tells sweat glands in your skin to release water (which cools you as it evaporates) and tells blood vessels near the skin surface to widen (so more warm blood flows near the air and heat escapes). At the same time, you feel thirsty and look for shade — automatic behaviors that help dump heat. This system works beautifully as long as the air is not too hot, you have water to make sweat, and the hypothalamus itself is healthy.

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What goes wrong

·Heat stroke happens when the body's cooling system is overwhelmed or blocked, and core temperature climbs above 104°F while the brain stops working right. There are two main paths. In classic (non-exertional) heat stroke, extreme outside heat — a heat wave, a closed car, a hot room with no air conditioning — overpowers the body's ability to dump heat, especially in people who already have weak defenses (elderly, very young, people taking drugs that block sweating like antihistamines or diuretics, or people who are dehydrated). In exertional heat stroke, the person is exercising so hard that their muscles make heat faster than the body can get rid of it, even if the air is not extremely hot; this happens to soldiers, athletes in two-a-day practices, or workers doing heavy labor in heat and humidity. Either way, once core temperature crosses 104°F, the hypothalamus itself gets damaged by the heat — the thermostat breaks — and normal cooling shuts down. Cells all over the body start to cook: proteins unfold, membranes leak, and organs fail.

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Hallmark signs

·Core body temperature over 104°F (40°C)
·Confusion, strange behavior, or trouble thinking clearly
·Seizures (sudden jerking or stiffening of the body)
·Loss of consciousness or coma
·Hot, dry skin (classic form) or hot, sweaty skin (exertional form)
·Fast, pounding heartbeat
·Fast, shallow breathing
·Severe headache

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Red flags · escalate now

·Core body temperature above 104°F (40°C)
·Confusion, bizarre behavior, or not making sense
·Seizures or loss of consciousness
·Stopped sweating in a very hot person (classic heat stroke)
·Rapid deterioration—getting worse by the minute

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Workup

·Core body temperature (rectal or esophageal thermometer)
·Serum creatine kinase (CK) and urine myoglobin
·Basic metabolic panel (BMP): sodium, potassium, creatinine, blood urea nitrogen (BUN)
·Complete blood count (CBC) with platelet count
·Coagulation panel: prothrombin time (PT), international normalized ratio (INR), activated partial thromboplastin time (aPTT), fibrinogen, D-dimer
·Liver function tests: AST, ALT, bilirubin
·Arterial blood gas (ABG) or venous blood gas (VBG)
·Electrocardiogram (ECG)

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Treatment

·Immediate rapid cooling: ice water immersion (if no cardiac arrest) or evaporative cooling (mist water on skin + fans)
·Stop active cooling at 38.5–39°C and monitor temperature every 15–30 minutes
·Large-bore IV lines (14- or 16-gauge) with cold normal saline bolus (1–2 liters rapidly, then titrate)
·Benzodiazepines (lorazepam 2–4 mg IV or midazolam 2–5 mg IV) for seizures or severe shivering
·Aggressive IV hydration + urine alkalinization (sodium bicarbonate to keep urine pH > 6.5) if rhabdomyolysis is confirmed
·Monitor and treat high potassium (hyperkalemia) (potassium > 5.5 mEq/L): calcium gluconate, insulin + glucose, and possibly dialysis
·Blood product transfusion (fresh frozen plasma, platelets, cryoprecipitate) if DIC causes active bleeding

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NCLEX trap

·Fever medicines like Tylenol or Advil do NOT work for heat stroke. Why? In fever, the hypothalamus (the brain's thermostat in the center of your head) is SET too high on purpose by infection signals, and those medicines reset it. In heat stroke, the hypothalamus is BROKEN from heat damage — it cannot control temperature at all. Medicines cannot fix a broken thermostat. Only physical cooling works: cold water, ice packs on the neck, armpits, and groin, and cool mist with fans. Start cooling immediately; do not waste time with pills.
·Cool FIRST, get labs SECOND. Heat stroke kills within minutes by cooking the brain and other organs. If someone's core temperature is over 40°C (104°F) and they are confused or passed out, start cooling RIGHT NOW — ice water, cold packs, fans. Do not wait for blood tests. The brain cannot wait. Labs help you track damage and guide later care, but cooling is the only thing that stops the injury from getting worse.
·Skin thermometers, forehead strips, and mouth thermometers are NOT accurate for heat stroke. You MUST use a rectal thermometer to measure core temperature — the true heat inside the body. The skin can feel only warm (maybe 38°C or 100°F) while the inside is dangerously hot (42°C or 108°F). Heat stroke diagnosis requires the real core number, and only rectal or sometimes esophageal probes give that. Do not trust the outside when the inside is on fire.
·Stop cooling when RECTAL (core) temperature reaches 38.5–39°C (about 101–102°F), NOT when skin feels cool. If you stop too early (say at 40°C core), temperature bounces back up and the brain keeps cooking. If you cool too far (below 38°C core), you risk hypothermia (body too cold), which brings its own dangers like dangerous heart rhythms. Use a rectal thermometer and stop at the right target. Feel is not enough.
·Heat stroke can happen with WET skin OR DRY skin. There are two types. Classic heat stroke (older adults in heat waves, no exercise) often shows dry skin because sweating has stopped. Exertional heat stroke (young athletes, soldiers, laborers working hard in heat) often shows drenched, sweaty skin — but the body is making MORE heat from muscle work than sweat can get rid of, so core temperature climbs anyway. Heat stroke is defined by core temperature over 40°C (104°F) PLUS brain problems (confusion, seizures, passing out) — not by whether skin is wet or dry. Never rule out heat stroke just because someone is sweating.
·Dehydration and heat stroke often happen together, but fluids ALONE do not drop core temperature fast enough to save the brain. Heat stroke needs BOTH: (1) rapid physical cooling (ice water, cold packs, fans) to stop the cooking, THEN (2) IV fluids to replace lost water, support blood pressure, and protect kidneys from the breakdown of muscle (rhabdomyolysis). Cooling comes FIRST — it is the only thing that stops ongoing brain and organ damage. Fluids come second to support the organs while they recover. Do both, in that order.

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