Heat Stroke: What you need to know

WATCH ABOVE: As temperatures across the country surge, Dr. Samir Gupta gives tips and information about heat stroke in this week’s On Call.

More On Call with Dr. Samir Gupta stories on

TORONTO — Temperatures are rising across the country, with many regions experiencing extreme heat warnings this week.

Accordingly, we thought it would be a good idea to talk about heat stroke — what exactly it is, and how people can prevent it.

Our bodies are designed to work within a narrow temperature range, which is a balance between the heat generated by our internal metabolic processes and the heat that we absorb from the outside environment.

READ MORE: Tips on how to sleep in hot weather and 3 things to avoid

Story continues below advertisement

When we start exceeding those narrow limits is when we can get into trouble.

The medical term for heat stroke is exertional or non-exertional hyperthermia (in other words, it can occur either with or without exercise).

It is defined by a rise in the body’s core temperature to above 40 C, caused by  environmental heat, and associated with signs of central nervous system dysfunction.

Such signs can include confusion, agitation, hallucinations, and even seizures.

The effect of a rising core temperature on body functions is complex.

The first thing that happens is that the body paradoxically increases its metabolic rate (generating more heat), and both respiratory and heart rates increase.

Once the core temperature reaches 42 C a number of the body’s enzymes stop working and inflammatory mediators are released by the body’s cells, essentially creating an inflammatory state.

The body also produces special proteins called “heat-shock proteins” as a protective mechanism.

However, eventually blood pressure drops, organs start shutting down one by one and severe heat stroke can lead to death.

Preventing heat stroke is not all that complicated for most of us.

Story continues below advertisement

The first piece is just being aware of environmental conditions and modifying outdoor activities accordingly.

That means not only knowing ambient temperatures, but also being aware of radiant heat from direct sun exposure.

Humidity levels are also critical because our body’s main mechanism to deal with heat is to produce sweat to dissipate heat through evaporation, but that evaporative heat loss becomes ineffective once the relative humidity hits 75 percent.

There is a particular measure called the wet bulb globe temperature (WBGT) which fully accounts for environmental heat load, including all three of these key factors (ambient temperature, radiant heat, and relative humidity).

It was developed by the military to determine the risk of heat stroke during outdoor physical training activities, but can also be very helpful to athletes planning outdoor sports on hot days.

Common sense approaches are key, including avoiding wearing too many layers, keeping well hydrated, and moderating exercise levels.

People should also keep an eye out for early signs of heat stroke, such as muscle cramps, weakness, lethargy, nausea, and dizziness.

Finally, we all need to be particularly vigilant about at risk groups which can develop heat stroke even without exercise, such as the elderly, and children.

Story continues below advertisement

In particular, cases of heat stroke in children who were left inside a closed automobile are seen every year.

Even when it’s moderate outside, inside car temperatures rise quickly due to a greenhouse effect, and kids should never be left in the car.

If in doubt, remember to get yourself or your loved one out of the heat right away, hydrate, start cooling yourself down with ice and cold water, and seek medical help.

Sponsored content