Exertional heat stroke
As medical transportation professionals, we have all been trained to recognize and treat heat illnesses. Heat cramps, heat syncope, heat exhaustion, and heat stroke are covered very well in the curricula we studied to obtain our certifications.
Exertional heat stroke (EHS) occurs when the core temperature is raised to dangerous levels due to physical activity. The temperature regulatory mechanisms are overwhelmed by excessive endogenous heat production or inhibited heat loss. Thermoregulatory failure occurs as a result of this hyper-thermic and hypermetabolic crisis. Temperatures may rapidly exceed 1040 Fahrenheit. Intra-cellular calcium dysregulation results in neuronal dysfunction and death. Central nervous system changes may be the first signs of exertional heat stroke. This is clearly a life-threatening situation and is particularly deadly if the temperature remains above 1060 F. Classic heat stroke usually occurs after prolonged heat exposure in infants, elderly, or unhealthy sedentary people whose body heat-regulation mechanisms are inadequate. It must be stressed that exertional heat stoke occurs during physical activity which results in overheating of organs. The brain is particularly sensitive. Hypothalamic temperature control mechanisms may malfunction. Circulatory failure, endotoxemia, severe lactic acidosis, hypokalemia, acute renal failure, rhabdomyolysis, and disseminated intravascular coagulation are common.
Risk factors for exertional heat stroke include:
- hot humid environment
- exercise intensity and duration
- inadequate heat acclimatization
- poor physical fitness
- previous heat-related incident
- existing medical conditions
Since the brain is so vulnerable, it’s not surprising that symptoms may begin with dizziness, irritability, unusual behaviors, seizures, confusion, collapse, change in personality, and aggression. Naturally, the usual heat-illness symptoms of tachycardia, hypotension, and hyperventilation occur, but may be accompanied by vomiting and diarrhea.
Immediate recognition is crucial. If a victim of heat exhaustion doesn’t improve within 20 minutes of the initiation of therapy suspect EHS. It’s probably reasonable to review your protocols with your medical director. Make sure that your cooling techniques meet the current standard of care. Sports medicine authorities state that a “rectal temperature is the only viable option” to assess body temperature in these circumstances. Your medical director may have some ideas about pharmacologic intervention. Note that even with external cooling, the internal temperature may remain elevated. Cognitive changes may remain for one to two hours after the hyper-thermic event. A third of EHS survivors continue to have neurologic impairment three months after the event.
I’m certain that you are in your care-giver mindset and thinking of potential patients, particularly those of you who do standbys at athletic events. What about you? Think about the level of exertion you must perform. Does body armor or bunker gear keep you cool? You already know about hydration. On those hot, busy days, you must remember to match fluid intake with sweat and urine losses. Keep you urine clear to light yellow. Use situational awareness to recognize symptoms in yourself and your partner. As the environmental conditions become more extreme, you need to take recovery time. It can take 10-14 days to acclimatize. Stay cool and hydrated as much as possible to avoid getting hot and dehydrated.
- Walter, EJ, Carraretto M, “The neurologic and Cognitive consequences of hyperthermia” Critical Care 2016: 210 (7):199
- www.exertinal-heatstroke.com Accessed June 30, 2017
- Kerry Stringer Institute, “5 pillars of heat stroke prevention”, University of Connecticut, 2017
- Binkley HM, Beckett J, et. al., “National Athletic Trainers’ Association Position Statement: Exertional Heat Illnesses”, Journal of Athletic Training, 2002;37(3):329-343