Tub Cooling for Exertional Heatstroke
William O. Roberts, MD, Department Editor
THE PHYSICIAN AND SPORTSMEDICINE - VOL 26 - NO. 5 - MAY 98
For an athlete who has exertional heatstroke, every minute counts: Rapid cooling can mean the difference between walking away from the event medical area and being hospitalized with potential sequelae. The fastest and simplest way to cool a dangerously overheated athlete is to put him or her in an ice-water bath. This method reduces body temperature by an average of 17°F an hour (1).
When is it done?
Any athlete with exertional heatstroke should be placed in an immersion therapy tub for rapid cooling. The diagnosis of exertional heatstroke can be made when a patient has a rectal temperature higher than 104°F along with central nervous system (CNS) changes. In my experience, athletes who have hyperthermia with CNS changes usually present with a rectal temperature higher than 107°F.
CNS depression often is first signaled by bizarre behavior and memory loss, as for the athlete's own name and event details. Athletes with heatstroke commonly lose the "hind limb" function and are unable to walk alone. Other possible CNS alterations include collapse, delirium, stupor, and coma; physical changes associated with heatstroke include shock and the ashen skin color of circulatory collapse. The skin is usually sweaty in exertional heatstroke; dry skin is rare in overheated athletes.
Early detection of heatstroke, with particular alertness in hot, humid conditions and with children and unacclimatized athletes, is crucial to an ideal outcome. If a patient is suspected of having exertional heatstroke, immediate care should include halting activity to stop internal heat generation, measuring rectal temperature, and, if possible, moving the patient to a cooler on-site environment (preferably air-conditioned).
If temperature measurement or tub cooling will be delayed, cooling with iced towels or cool-water sponging should be started while the athlete is being moved to a tub. For a patient who has heatstroke, the immediate priority should be body cooling; fluid replacement should be initiated during or after the cooling process. The hydrostatic pressure of immersion therapy augments blood pressure, increasing central volume, which may compensate to a degree for the delay in fluid replacement.
How is it done?
Tub cooling can be done with readily available equipment and supplies, but the protocol should be planned and the supplies obtained in advance. For athletic events that pose a risk of hyperthermia and heatstroke, medical teams should have the supplies and equipment on hand to initiate immediate on-site cooling.
The tub must be deep enough to submerge the trunk, including the high-conductivity areas of the neck, axilla, and groin (figure 1). A plastic wading pool, inflatable raft or boat, concrete-mixing tub, bath tub, or any shallow tub can be used. Rubbermaid (Wooster, Ohio) makes a sturdy, reusable tub that has been tested at the Falmouth Road Race and sells for about $40.
The legs and arms can be either immersed or left out of the tub. The advantage of a smaller tub that leaves the legs out (figure 2) is less worry that the patient's head will slide into the water. The advantages of having the legs and arms submerged in the tub are that hydrostatic pressure augments blood pressure in the face of early shock and that more skin is exposed to the water, increasing the surface area for heat exchange.
The tub is filled with water and one to two 40-lb bags of ice until the depth is 8 to 10 in. When ice is not available, the tub can be continuously filled with water from a freely flowing garden hose, which is usually 55°F and works well for cooling, though it is not as effective as ice water. The patient is submerged in the tub with the head supported either by a medical staff member or by the rim of the tub.
The athlete should be checked every 5 to 10 minutes for rectal temperature, CNS status, and vital signs. To prevent overcooling, he or she should be removed from the bath when the rectal temperature drops to 102°F. An athlete with a temperature of 108°F to 110°F can be cooled to 102°F in 15 to 30 minutes. An indwelling rectal probe with a constant read-out thermometer (Thermistor, Cole-Parmer, Chicago) is a convenient measuring tool. The athlete must also be observed for airway and breathing problems, seizure, muscle spasms, and mental status changes during and after the cooling process. After each use, the tub should be cleaned with a bactericidal, viricidal solution (ie, dilute bleach solution) and rinsed with clean water.
What if no tub is available?
If no tub is handy, the athlete can be continuously doused with cool water from a garden hose; packed in ice while lying on a cot; treated with ice packs placed in the axilla, groin, and neck areas; or sponged with water and cooled in front of an electric fan.
The sponge-and-fan method does not work well in high humidity, so in that case the athlete should be put in an air-conditioned vehicle or building to make the method more effective. None of these methods, however, cools the hyperthermic athlete as rapidly as immersion in a tub of ice water.
Who can leave without hospital evaluation?
Athletes who have been cooled on site are usually observed for 20 to 60 minutes before release from the medical area. An athlete who has had exertional heatstroke (but is otherwise in good health) can leave the medical area of a road race or sports event when he or she is taking oral fluids, is normothermic, displays normal vital signs, and demonstrates good cognitive function. If there are residual symptoms or any possibility of continuing vascular or CNS dysfunction, the athlete should be transferred to an emergency facility for further evaluation and treatment.
In a setting where exertional heatstroke is not expected or routinely treated, it may be prudent to have the athlete evaluated in an emergency facility. But cooling treatment should not be delayed by a transfer because the product of time and temperature elevation directly affects morbidity in heatstroke.
Dr Roberts is a family physician at White Bear SportsCare in White Bear Lake, Minnesota, and medical director of the Twin Cities Marathon. He is a fellow of the American College of Sports Medicine, a charter member of the American Medical Society for Sports Medicine, and an editorial board member of The Physician and Sportsmedicine.
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