Heat stress: fluid and electrolite imbalance can be fatal

June 30th, 2005 by Julie Ferguson

Heat kills. This is a fact that was underscored publicly last week with the release of autopsy results for Scott Laio, a 20-year-old Boston College student who collapsed and died after rowing in the Dad Vail Regatta in May. The Philadelphia Medical Examiner’s Office attributed the cause of death to a fluid and electrolyte imbalance and heat stress. Physical exertion causes the body to lose fluid through sweat, and it’s essential that fluid be replaced at regular intervals. The U.S. Army – an entity that has some amassed some deep knowledge in the business of physical exertion in conditions of extreme heat – recommends minimum and maximum fluid replacement guidelines(PDF) for varying levels of exertion, as well as other heat injury prevention resources.
Heightened risk for some workers
Here in New England, we’ve been in the throes of an oppressive heat wave for the last week that has left me sluggish, and wistfully hoping for a late-afternoon thundershower at the close of each day. But as I slip from air-conditioned office to air-conditioned car, I think of the workers who have little relief from the heat. Outdoor workers such as agricultural workers, landscapers, lifeguards, construction crews, and road workers are particularly at risk for heat-related illnesses. And pity the outdoor workers whose jobs call for protective equipment, like firefighters and pesticide workers – the risks are that much greater because heavy gear can interfere with sweating, which is the body’s natural cooling mechanism.
ErgoWeb has a report on new heat stress resources for firefighters and other workers who work in environments that put them at heightened risk for heat disorders. The article reports on research conducted by Tom McLellan and Glen Selkirk:
“Working with Toronto Firefighters in ambient summer conditions, the researchers compared active and passive cooling strategies in combination with different levels of hydration. They found that the active approach — a combination of fluid replacement and misters or the submersion of the forearm and hand in cool water — effectively brings down the body’s core temperature. The study found that this combination was twice as effective as the passive approach — hydration and the removal of the protective clothing only.
This research offers corroboration to a practice that many of us may have intuitively known in our day-today lives, but that may nor be widely employed in work settings.
Preventing heat-related illnesses
Of course, workers don’t need to work outdoors, in heavy clothing, or in extreme conditions to be at risk. A sudden or prolonged heat wave can put many other workers at risk. And a variety of individual factors such as age, weight, physical conditioning, medication, alcohol, caffeine, and salt can heighten the risk.
Employers would do well to review OSHA’s Heat Stress Guide and conduct self-assessments about their own seasonal readiness for worker heat stress prevention. The article Beating the Heat by Donna Miles in Occupational Hazards offers some good advice. Here are some tips from the article:

  • Encourage workers to drink plenty of water – about a cup of water every 15 to 20 minutes, even if they are not thirsty – and avoid alcohol, coffee, tea and caffeinated soft drinks that dehydrate the body.
  • Help workers adjust to the heat by assigning a lighter workload and longer rest periods for the first five to seven days of intense heat. This process needs to start all over again when a worker returns from vacation or absence from the job.
  • Encourage workers to wear lightweight, light-colored, loose-fitting clothing. Workers should change their clothes if they get completely saturated.
  • Use general ventilation and spot cooling at points of high heat production. Good airflow increases evaporation and cooling of the skin.
  • Train first-aid workers to recognize and treat the signs of heat stress and be sure all workers know who has been trained to detect early signs of heat-related illness. Permit workers to interrupt their work if they become extremely uncomfortable.
  • Consider a worker’s physical condition when determining fitness to work in hot environments. Obesity, lack of conditioning, pregnancy and inadequate rest can increase susceptibility to heat stress.
  • Alternate work and rest periods, with rest periods in a cooler area. Shorter, more frequent work-rest cycles are best. Schedule heavy work for cooler times of the day and use appropriate protective clothing.
  • Monitor temperatures, humidity and workers’ responses to heat at least hourly.