When heat waves become killers

As the southern states of Australia head in to winter, it’s hard to recall the oppressive heat wave that killed more than 200 hundred people in South Australia and Victoria last summer.

While we are acutely aware that our infrastructure may buckle or shut down under high temperatures, we underestimate the power of heat waves to quickly kill those most vulnerable: the elderly living alone, the mentally ill and the very young.

The number of heat wave deaths in South Australia and Victoria was directly linked to the number of elderly people living alone, who were not monitored by family or friends. Global warming did not cause the high death rate as some environmental groups have said. It was neglect.

Unlike many communal Asian cultures where the elderly are revered, in Australia our attitude to the elderly must take some of the blame for the high death rate.

According to Dr Monika Nitschke, the principal scientific officer at the South Australian Department of Health, medications such as diuretics and anti-hypertensive drugs used to lower blood pressure, may inhibit the ability to sweat or interfere with the reduction of temperature regulation mechanism in the central nervous system.

“An overheated core causes an inflammatory response through out the body, which, in combination with other mechanisms, can inhibit the body's natural mechanism for cooling down. You get hotter and hotter,” she said.

“Elderly people here (SA) died very quickly in unconditioned houses, - especially if they had no one to look after them.

“We need heat wave action plans and prevention plans which extend to the type of houses we live in, we can make cities and suburbs more livable under heat stress.”

Heat and the body

Think of the body as a thermostat. It operates best at its core temperature of 37C. Walk outside on a hot day and the central nervous system immediately starts working to cool you down. It diverts blood away from the internal organs and towards your skin. The blood carries the heat to the extremities.

Meanwhile, the sweat glands start to release water, which cools as it evaporates on the skin. On a very hot and humid day, it's harder to radiate heat away from your body due to the high water content in the air.

Infants and small children have a very slow sweat response, and their hearts aren't always strong. Obese people can't dissipate heat quickly and may have fewer sweat glands. Mentally ill and elderly patients sometimes take drugs that inhibit perspiration.

The heart does much of the hard mechanical work. That's OK if you're 16 but it's not good if you're 86. It can lead to arrhythmia or to a heart attack. As Dr Nitschke said, some medications for high blood pressure won't let the heart beat faster, which means it can't push blood away from the core organs quickly enough.

Once the core temperature gets above 40C, you're in serious trouble. High internal temperatures lead to increased pressure in your skull and decreased blood flow to the brain. Not a good combination.

Very high internal temperatures, for example 49C, can directly destroy the cells in your body. At this stage you're dying and quickly.

Chicago

We know a lot about the social effects of heat waves because they have been studied intensely and none more so than the great Chicago heat wave of 1995 which killed more than 500 people.

On July 16, 2005 Chicago felt tropical. The temperature hit 41C. For a week the heat ran between the low and high 30's. The night temperatures didn't provide any relief. Chicago's houses and apartments baked.

The city set new record for power use. At one point 49,000 Chicagoans had no power. Just like the 200,000 Melbournians and Adelaidians who suffered power failures during the heat wave.

By Friday evening on July 18, thousands of Chicagoans had developed severe heat related illnesses. Paramedics couldn't keep up with the emergency calls and city hospitals were inundated. The most over crowded place in the city was the Cook County Medical Examiners Office where police transported hundreds of bodies for autopsies.

By Saturday - just three days in to the heat wave - the morgue was full and a fleet of refrigerated trucks were used to store the bodies.

During the peak of the heat wave from January 28 to February 6, the South Australia Government had to create a temporary morgue, as the main morgue at the Forensic Science Office was full with 72 bodies.

They bought in refrigerated trucks. From January 28 to January 30 the Melbourne morgue dealt with more than twice as many bodies as in the same time last year.

The state coroner Judge Jennifer Coate said they were being kept elsewhere. "We'd made arrangements for appropriate facilities around Melbourne - that includes hospitals and funeral directors largely," she said.

Ambulance Victoria operations manager Paul Holman said the service went in to major disaster mode as it struggled to respond to 1,600 jobs a day - double the normal number.

The US Centre for Disease Control and Prevention did a thorough study of individual-level risk factors for heat wave victims and they came up with a list of conditions of vulnerability: living alone, not leaving home daily; lacking access to transportation; being sick or bedridden; not having social contacts nearby, and not having an air conditioner.

According to Eric Klinenberg who wrote Heat Wave: A Social Autopsy of Disaster in Chicago, hundreds of Chicago residents died alone, behind locked doors and sealed windows, out of contact of friends, family and neighbours, unassisted by public agencies or community groups.

“The only way to prevent another heat disaster is to address the isolation, poverty and fear that are prevalent in so many American cities today. Until we do, natural forces that are out of our control will continue to be uncontrollably dangerous,” Eric Klinenberg said.

Dr Nitschke said the death rate in South Australia was considerably reduced where elderly people had good social networks, air conditioners and the existence of a rudimentary heat wave plan.

We would do well to look to the hard lessons learnt in Chicago.