Heat stroke: symptoms, duration, urgency, what to do?

[Mise à jour le 14 juin 2022 à 17h33] When it is hot, our body reacts by activating its cooling system. The objective: to maintain the internal temperature at 37°C even if it is colder outside. How ? Over there vasodilatation and by the sweating. The vasodilatation of the vessels that one feels well when it is hot (heavy legs, swollen hands and feet, hot surface of the skin) makes it possible to evacuate the heat towards the surface of the body. The sweat allows, in turn, cool the surface of the skin. The problem is that in infants these cooling mechanisms are not always up to snuff, and in older people they don’t work as well. As a result, the youngest (especially before 4 years) and the oldest are at risk of get dehydrated faster and see their internal temperature exceed 37°C. Heatstroke is a medical emergency who engages the
vital prognosis.

Definition: what is heat stroke?

Heat stroke is overheating of the body with a temperature above 40 degrees. The body can no longer cope with the increase in internal temperature linked to muscular activity and/or an overheated atmosphere (heat wave). We thus distinguish the classic heat stroke in people exposed for a long time to a hot and humid ambient temperature (for example, staying for hours in a car or in a RER in the heat) of exercise heatstroke which occurs during intense and sustained physical activity (classic heat stroke). Classical heat stroke occurs in epidemic form during heat waves, and predominates in the elderly, frail, suffering from chronic pathology: cardiovascular, pulmonary or mental.

What is exercise heat stroke?

Exercise heat stroke occurs after a intense and sustained physical activity in a hot atmosphere, sporadically and affects young, healthy subjects such as athletes high level and military personnel. Symptoms are similar to classic heatstroke except that the subject’s skin is moist due to heavy perspiration rather than dry.

What are the symptoms of heatstroke?

The diagnosis of classic heat stroke is based on hyperthermia and consciousness disorders after exposure to a hot and humid atmosphere. Among the symptoms of heatstroke:

  • a sudden fever that reaches or exceeds 40°c
  • palpitations
  • severe headache
  • of the redness diffuse
  • the skin is hot and very dry (sweating stops) / in athletes, the skin is hot and rather moist.
  • of the vomiting
  • diarrhea
  • mental confusion, delirium and severe state of agitation

How long does heat stroke last?

In mild and quickly treated forms, heat stroke usually lasts less than 12 hours.

What to do ?

You must seek medical assistance as soon as possible: call 15. Waiting :

  • put the subject in the shade
  • cool it by spraying it with cold water and fanning it
  • or give a cold shower or a cool bath.

No adjuvant pharmacological treatment that can accelerate cooling has shown its effectiveness.

What are the risks of heatstroke?

Heatstroke is a medical emergency because it can be life-threatening. It can lead to neurological disorders (delirium, convulsions or coma) and then so-called “multi-visceral” failures and evolve towards death. Multiorgan failures are:

  • Cardiovascular failure: low blood pressure, shock
  • Respiratory failure: polypnea, profound hypoxemia
  • Renal failure : oligo-anuria, moderate to severe renal insufficiency.
  • Hematological failure : hemostasis disorders with thrombocytopenia, even fibrinolysis and disseminated intravascular coagulation (DIC).
  • Liver failure (rarer).

Among the most severe complications seen as a result of heat stroke are:

  • Acute coronary syndrome
  • Heart rhythm disorders, conduction disorders.
  • Bleeding complications
  • Acute Respiratory Distress Syndrome (ARDS)
  • Acute pancreatitis
  • Fulminant hepatitis.

How to avoid it?

  • Drink water regularly without waiting to be thirsty (at least 1.5 L per day). First people affected, infants and the elderly. The latter who sometimes do not feel thirsty must force themselves to drink.
  • Avoid physical exertion and sports which increase your internal body temperature.
  • Wear light, loose clothing because they promote air circulation, rather light in color so as not to retain heat.
  • Freshen up several times a day : do not hesitate to take showers, to get your head wet, to use misters or damp cloths.
  • The fans? They provide a pleasant feeling of freshness through the circulation of air, but when the air is hot, it stays hot and in fact does not cool you down. So it’s not enough to cool you down. It is best to get wet regularly.
  • What to drink? Avoid alcohol, sugary drinks, and high caffeine content (coffee, tea). Prefer still and sparkling water (enriched with salt) and fresh fruit juices.
  • What to eat? Continue to eat normally, preferably favoring fruits and vegetables: salads of raw vegetables, fresh soups, but also dairy products (liquid yoghurts, milkshakes, etc.).
  • cover your head. Your choice of hats, caps, or scarves will save you from sunstroke.
  • Even if the heat is tiring, don’t take a nap in the sun!
  • Stay in well ventilated and cool rooms. Close the shutters and open the windows to let in the air. If your apartment is really hot, arrange to stay in cool or air-conditioned places for at least two or three hours during the day (department stores, cinemas, public places).


Heat wave recommendations, SFMU, 2011.

Heat stroke Heatstroke C. Rahmoune a , A. Bouchama b, Elsevier, 2004

#Heat #stroke #symptoms #duration #urgency

Leave a Reply

Your email address will not be published.