THE CANADIAN PRESS -- TORONTO - The heat dome stalled over much of Canada not only makes people miserable as they try to cope with sizzling temperatures, but it also can cause severe -- even potentially fatal -- health effects.
Those most vulnerable to extreme heat and humidity are the elderly and very young children, as well as the homeless and marginally housed, doctors say.
Among the most worrisome disorders that can arise from prolonged exposure to soaring numbers on the thermometer are heat exhaustion and heat stroke, said Dr. Mark Bonta, an internal medicine specialist at Toronto General Hospital.
With heat exhaustion, a person's normal internal temperature rises to 40 C, he said Tuesday.
"Think about maybe being out on a hot day too long at a concert. You feel a little bit dehydrated, but your mental status is OK ... your cognition is not clouded, you're able to communicate, you're awake.
"And you'll be experiencing sweating because that's your body's natural mechanism of evaporation, of losing heat."
Heat stroke is an exacerbation of heat exhaustion, setting in when one's internal temperature spikes above 40 degrees, said Bonta. Patients "will often be dehydrated or dry when you look at their skin because they've lost their sweat and their body's ability to thermoregulate. And their mental status is abnormal, so they may present in a coma, they may present confused, not aware of where they are."
Bonta said those brought to hospital with heat stroke have a 25 to 60 per cent risk of dying from the condition, which can lead to heart, kidney and liver failure, and in some cases a condition that causes massive spontaneous internal bleeding.
"What we have seen is that the people who are most at risk of serious illness or death from extreme heat are people who are elderly, people who already have a chronic medical condition, very young infants -- and particularly if they're living in poor-quality housing with poor ventilation and no air-conditioning," said Dr. David McKeown, Toronto's medical officer of health.
"Those are really the folks we worry about dying during a heat wave."
In Toronto, the Red Cross delivers bottled water to those most vulnerable to extreme heat conditions, including the homeless living outdoors, the marginally housed and seniors, either directly or through community agencies, said spokeswoman Tanya Elliott.
"We also have volunteers who staff a heat information line (416-480-2615) and they take calls from the public who are maybe looking for information about how to stay safe in the heat," said Elliott, noting that other Red Cross agencies across the country may have similar programs.
"Occasionally, we do get calls from people who might be concerned that they're experiencing heat-related illness, so they have some information to help people determine whether they should be calling 911."
McKeown noted that Canadians with an underlying medical problem, such as heart disease, asthma or chronic bronchitis, may also find their condition worsening in severe heat and humidity.
"So someone with a respiratory condition who finds it difficult to breathe or someone with a heart condition who's experiencing shortness of breath or chest pain, it can be in fact related to their heat exposure."
When it comes to infants and very young children, McKeown said parents and caregivers should keep them in a cool room, not overdress them and make sure they drink plenty of water or other non-caffeinated fluids. They should never be left unattended in a overheated vehicle, he stressed.
Seniors also need to take special precautions during a heat wave, even if they don't venture outside into the glaring sunshine, said Robin Joy, vice-president of marketing for Caring.com, a website aimed at caregivers of adults with dementia or other health problems.
"If their home gets really hot ... (and) if they're not drinking enough fluids, they still can get heat stroke or heat exhaustion, even if they're inside," Joy said from San Francisco.
She has some advice for seniors, although it can pertain to adults of any age:
--Drink plenty of fluids such as water, but avoid dehydrating fluids such as alcohol and caffeinated beverages like coffee, tea and colas.
--Wear a hat, sunglasses and sunscreen when outdoors, especially when spending time in direct sun, which should be of limited duration.
"And third, if possible, is to have working air-conditioning or electric fans in their house. And if that doesn't exist, then to make sure you spend a couple of hours in a setting that does have air-conditioning, such as going to a movie theatre, shopping mall or a seniors centre."
Joy said many older people also have a tendency to overdress, even in weather that younger people find sweltering.
"Seniors sometimes get in the habit of dressing a certain way, oftentimes putting on a number of layers because they're sensitive to the cold.
But they sometimes don't realize that their body is actually really hot, so they may not have as much sensitivity to realize that it's time to take off
some of those layers."
She said a family member, caregiver or neighbour checking in on an older person can help with that: "Just make sure to ask, you know, 'Do you really need that sweater on right now? Maybe you could take it off. It's really hot outside. It's really hot in here.'"
Checking in on seniors and other vulnerable people living on their own at least once or twice a day is essential, experts say.
"That check-in may be just a phone call or ideally if you can visit or ask a neighbour to visit," said Joy. "We think that's a big thing just to make sure seniors are feeling OK in this period of intense heat and their air-conditioning is working, or if not that they have the help they need to get to an air-conditioned location."
"Sometimes just waiting for public transportation in the middle of the heat can be really difficult, so helping to organize a ride or a taxi service can make a big difference."
Sheryl Ubelacker, Health Reporter, The Canadian Press