Sports Medicine Research: In the Lab & In the Field: Clinical Pearl: Prevention and Treatment of Exertional Heat Stroke (Sports Med Res)
Wednesday, September 12, 2012

Clinical Pearl: Prevention and Treatment of Exertional Heat Stroke



Julie K. DeMartini, MA, ATC/LAT and Douglas Casa, PhD, ATC, FNATA
Korey Stringer Institute
Human Performance Laboratory, Department of Kinesiology
University of Connecticut

The Korey Stringer Institute (KSI) at the University of Connecticut (www.ksi.uconn.edu) is striving to educate personnel involved with athletic competition and implement policy changes pertaining to the prevention, recognition, and treatment of exertional heat stroke (EHS) as well as other common causes of sudden death in sport. KSI provides first rate information, educational resources, and advocacy for the purpose of minimizing sudden death among athletes.  Please visit the KSI website (www.ksi.uconn.edu) to learn more about our mission and current endeavors.
EHS is one of the leading causes of sudden death among student athletes.  Despite advancements being made in research pertaining to the prevention, recognition, and treatment of this condition, deaths arising from EHS are becoming more frequent.  According to the North Carolina National Center for Catastrophic Injury, over the last 5-year reporting period (2004-2009) athlete deaths from EHS showed a drastic increase compared to previous years.  Furthermore, data collected from 2010-2011 continues to show an increasing trend in athlete deaths.
The most common time for an EHS to occur is during summer conditioning sessions at the collegiate and high school levels and during pre-season practices in high school football.  While many prevention strategies can be implemented to decrease the risk of EHS, not all cases of EHS can be prevented.  However, if EHS is correctly recognized and immediately treated via whole-body cold water immersion there is a 100% survival rate. Therefore, it is important for all personnel involved in athletics (i.e. athletic trainers, team physicians, coaches, strength and conditioning coaches, etc.) to consider the equipment needed and steps necessary to properly treat an EHS victim with the use of cold-water immersion. 



Prevention of Exertional Heat Stroke
·        Conduct a thorough, physician-supervised pre-participation medical screening prior to the start of the season to identify athletes who may be predisposed to heat illnesses based on risk factors for heat illness or a history of heat illness.
·        Athletes should be acclimatized to the heat gradually over a period of 7 to 14 days.  Heat acclimatization involves progressively increasing the intensity and duration of, as well as phasing in protective equipment (if applicable) during periods of high environmental stress.
·        Athletes should maintain a consistent level of optimal hydration and replace fluids lost through sweat during games and practices (See the National Athletic Trainers’ Association Position Statement: Fluid Replacement in Athletes).  Athletes should have free access to readily available fluids at all times, not only during designated breaks.  Instruct athletes to drink sodium-containing fluids to replace sodium losses in the sweat and urine.  Fluid consumption/replacement should aim to help athletes maintain less than 2% body mass change (measured pre and post-practice) and keep their urine color clear to light yellow. These strategies will lessen the risk of acute and chronic dehydration and decrease the risk of heat-related illnesses.
·        The sports medicine staff must educate relevant personnel (eg, coaches, administrators, security guards, EMS staff, athletes) about preventing EHS and the policies and procedures that are to be followed in the event of an incident.  Signs and symptoms of a medical emergency should also be reviewed. 
·        Ensure that appropriate medical care is available and that all personnel are familiar with exertional heat illness prevention, recognition, and treatment. Ensure that certified athletic trainers and other health care providers covering practices or events are allowed to evaluate and examine any athlete who displays signs or symptoms of heat illness and have the authority to restrict an athlete from participating if heat illness is present.
·        Encourage athletes to sleep at least 6-8 hours at night in a cool environment and eat a well-balanced diet, including maintaining proper hydration.  Athletes should also be encouraged to rest in a cool environment during periods of inactivity (off days, in between double session practice days, etc.) to maximally recover from preceding practice sessions. Rest periods should be implemented around meal times by allowing 2 to 3 hours for food, fluids, electrolytes (e.g., sodium and potassium), and other nutrients to be digested and absorbed before the next practice or competition. Develop event and practice guidelines for hot, humid weather that anticipate potential problems encountered based on type of activity, heat acclimatization status of athletes, and wet-bulb globe temperature (WBGT) or heat and humidity as measured by a sling psychrometer.  If environmental conditions are high, activity should be delayed, rescheduled, or moved into an air-conditioned space (if possible). Modifications can include moving the activity to early in the morning/late in the evening to avoid the hottest time of the day, altering practice drills to avoid high intensity activity, and altering practice to limit the amount of protective equipment worn by players (if applicable).  Identify individuals who are particularly susceptible to exertional heat illnesses.  Extreme caution should be used in monitoring athletes during periods of high environmental conditions and preventative steps should be made.  In addition, emergency supplies and equipment should be on-site and easily accessible and in good working order to allow for immediate intervention and treatment if needed.
Plan rest breaks and modify the work:rest ratio to match the environmental conditions and the intensity of the activity. Exercise intensity and environmental conditions should be the major determinants in deciding the length and frequency of rest breaks.  Breaks should occur in the shade (if possible) and should allow enough time for all participating athletes to consume appropriate fluids.  The following list includes the items necessary to successfully treat an EHS patient.  It is critical that these items are in a central location that is easily accessible if quick access is needed. In addition, all personnel directly involved with athletic participation, should know where these items are stored and how to properly use them.

Treating Exertional Heat Stroke: Emergency Treatment Supplies
·        Cold water immersion (CWI) tub: This is the primary piece of equipment used to treat EHS.  They are inexpensive, durable, and can be reused.  There are several size options but the 150-gallon tub is recommended due to the ability of easily immersing the entire body.
·        Water: The water supply should be easily accessible at all venues.  If this is not feasible, there should be a quick mode of transportation (i.e. gator, golf cart, etc.) to take an EHS patient to the water source.
·        Ice: An unlimited and easily accessible supply of ice should be available. Ice will be necessary to provide a cold enough water temperature for acceptable cooling rates. It is recommended to keep several coolers of ice next to the immersion tub and only add the ice when an EHS case has been recognized. 
·        Coolers/ice chests: As mentioned above, coolers are necessary to store the ice next to the immersion tub.  This method allows immediate access to the ice, avoids wasting ice if immersion is not necessary, and ensures the water will be cold when initially immersing the athlete.
·        Towels: A large towel/sheet should be available to be placed underneath the EHS victims armpits to prevent their head from being submerged.  The sheet/towel should be placed in front of the victim’s body across their chest, stretched underneath each armpit, and each end should be held by a clinician behind the athlete when they are seated in the tub.  This will allow the clinician to support the weight of the athlete and to prevent their head from falling beneath the water..  In addition, spare towels should be kept in ice water for a back-up method of body cooling if needed.
The following provides the step by step processes to most effectively treat an EHS patient.  This process should be reviewed by all personnel involved with athletic participation to ensure proper treatment if an EHS cases arises. The goal for any EHS victim is to lower the core body temperature to less than 102.5°F (38.9°C) within 30 minutes of collapse.  The length of time core body temperature is above the critical core temperature threshold (105°F [40.5°C]) dictates any morbidity and the risk of death from EHS.  

Treating Exertional Heat Stroke: Steps to Ensure Survival
·        Activate the Emergency Medical Service (call 911)
·        When EHS is suspected, remove clothes and equipment and promptly immerse the body (trunk and extremities) into a pool or tub of cold water. Place a large towel or sheet underneath the athlete’s armpits to support the athlete and prevent their head from being submerged.
·        Water temperature should be approximately 35°F (1.7°C) to 59°F (15°C) and continuously stirred to maximize cooling. 
·        Cooling rates with cold water immersion may vary for numerous reasons (e.g., amount of body immersed, body type, temperature of water, amount of stirring), but a general rule of thumb is that the cooling rate will be approximately 0.37°F/min (0.2°C/min) or about 1°F every 3 minutes (or 1°C every 5 minutes). 
·        If cold water immersion is not available, other modalities such as wet ice towels rotated and placed over the entire body or cold-water dousing with or without fanning may be used but are not as effective as cold-water immersion.
·        If a physician is present to manage the athlete’s medical care onsite then initial transportation to a medical facility may not be necessary so immersion can continue uninterrupted.  If a physician is not present, aggressive cooling should continue until the athlete is normo-thermic before emergency medical system transport. 
·        Policies and procedures for cooling athletes before transport to the hospital must be explicitly clear and shared with potential EMS responders so that treatment by all medical professionals involved with a patient with EHS is coordinated.
In conclusion, while exertional heat stroke is one of the leading causes of sudden death in sport, implementing proper prevention strategies can greatly minimize the occurrence of this condition in athletes.  Although not all cases can be prevented, proper education of medical personnel and coaches can teach basic treatment strategies for EHS.  With proper treatment, including prompt recognition of the condition, sudden death resulting from EHS can be eliminated as treatment via aggressive cooling using cold water immersion has been shown to have a 100% survival rate when utilized immediately.  For more information on EHS please visit the KSI website (www.ksi.uconn.edu).

2 comments:

Aaron Bottinick said...

I felt this was a very thorough description of the prevention and treatment of exertional heat stroke. From my own experience working marathons, I understand the urgency of attempting to quickly decrease core temperature in athletes suspected of suffering from heat illness/ exertional heat stroke. I believe cold-water immersion may be the most effective and safe method of decreasing core body temperature.

In a recent lecture, the topic of accurately recording core body temperature was discussed. There have been studies suggesting that the differences in temperature recorded by rectal and aural thermometers increases as core temperature increases. A discussion followed on whether or not rectal temperature should be taken for an athlete suspected of suffering from heat stroke. While it may provide a more accurate measurement of core temperature, is it worth the time and effect in a potentially life-threatening situation? I would be interested to hear others opinions.

Douglas Casa, PhD, ATC said...

This is why you should always get a rectal temp in a suspected heat stroke:

1) Determine if it is or is not EHS
Is it Heat Exhaustion?
Is it a Head Injury?
Is it Hyponatremia?
Is it a blood glucose issue?
Is it something else?

2) Determine when to stop cooling

3)Determine if EHS occurred (which influences recovery plans- if you just assume EHS w/o temp then what condition are you treating?)

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