Treat the Heat

Heat-Related Injuries

This time of year (summer) is notorious for heat-related injuries (HRIs) to occur, but this does not exclude other times of the year, for example, winter athletic training in an indoor athletic training facility or a firefighter who has been exposed to elevated temperatures for extended periods. That said, HRIs can progress into a life-threatening process and should be taken seriously, and your skills as a critical care provider are sure to benefit any patient you come across who has an HRI.  Please remember to prioritize your treatments, monitor your patient’s vitals, and mental status often (Hifumi, Kondo, Shimizu, & Miyake, 2018). Vigilance is fundamental and will be vital in recognizing changes in your patient’s condition and ensuring you are prepared to manage more complex sequelae.

As I begin to discuss this topic, I want to be clear that there are two forms of heatstroke. The first of the two is typically called classical or sometimes non-exertional. This type of heatstroke primarily impacts elderly and young patients, and it can also affect patients who take specific medications. The other form of heatstroke is referred to as exertional heatstroke, and according to Hifumi et al. (2018) is associated more often with athletes, soldiers, and firefighters. There are some differences; however, the critical element is the neurological aspect of the assessment. So, please remember that there may be a difference in onset of events that led up to their current condition. However, the focus should be on managing him or her effectively and according to the evidence.

Heat Stroke versus Heat Exhaustion

Within this blog I want to discuss HRIs, their acute effects, long-term effects if not treated, who is at highest risk, management from the emergency medical services, helicopter emergency medical services (HEMS), and critical care transport perspective. HRIs is comprised of varying levels of injuries, in order from the least critical to the most critical, however, regardless of what stage a patient is in this should not change your priorities and continued assessment of the patient:

  1. Heat cramps
  2. Heat syncope
  3. Heat exhaustion
  4. Heat Stroke
    • Classical heat stroke or non-exertional
    • Exertional heatstroke (Mahant, 2015; Gopinath, 2018; Hifumi, Kondo, Shimizu, & Miyake, 2018).

The objective of this article is geared toward heat stroke and heat exhaustion, so for the sake of brevity, we will focus on those only. With that being said, let us first breakdown what specifically heat stroke and heat exhaustion are and then discuss who is at risk, symptoms, and appropriate management. Keep in mind that when determining which of the two injuries you are dealing with, heat stroke will present with an alteration in mental status (AMS), this is the key take away from the blog(Cheshire, 2016; Nichols, 2014; Centers for Disease Control and Prevention (CDC), 2018).

Similarities and Differences

Heatstroke is life-threatening that must be managed quickly, or your patient has the potential to progress to multiorgan dysfunction syndrome, lasting neurological deficits to include, encephalopathy, rhabdomyolysis, and disseminated intravascular coagulation (Hifumi, Kondo, Shimizu, & Miyake, 2018; Walter, 2016; Gopinath, 2018). Heatstroke presents with a core temperature usually greater than 40 degrees Celsius (104 degrees Fahrenheit), warm, dry skin or sweating, tachycardia, tachypnea, hypotension, and always an AMS or neurological dysfunction; however, the critical component is the AMS (Walter, 2016).

That being said, a study in The Journal of the American Medical Association (JAMA) showed that any temperature above 41.1 degrees Celsius (106 degrees Fahrenheit) “measured anywhere on the body” was also associated with heat stroke (Kilbourne, Choi, Jones, & Thacker, 1992). However, keep in mind that an individual who has been in the heat for any period and has an AMS regardless of temperature should be treated accordingly. So be keen and perform a quality mental status assessment, and if possible, continue checking mental status routinely to look for changes or deterioration.

Neuropathophysiology of Heat Stroke

Before moving on, I think it is essential to discuss the potential causes for the AMS and or neurological dysfunction. One might assume that this is a result of the hypotension related to vasodilation, that response is associated with sweating which cools the body as a heat-related response. This seems plausible as likely culprit to lead to poor perfusion of the brain. But, it appears that the neurological dysfunction is more associated with the release of cytokines, similar to what a person in septic shock would experience. This release likely causes cerebral ischemia and edema, which can affect the nerve cells of both the cerebral cortex and cerebellum (Miyake, 2013). It appears Miyake (2013) believes that cytokines cause swelling in the brain, that ultimately proceeds to central nervous system dysfunction (CNS). The research I found was not as specific as I would like nor did not go into a considerable amount of detail concerning this process so mainly I am paraphrasing as much as I can without muddying the water too much.

Heat Exhaustion

Heat exhaustion, on the other hand, presents with signs of hot flushed skin, sweating, and a core temperature less than 40 degrees Celsius (104 degrees Fahrenheit); however, no mental status change will exist, although anxiety may be present, however, not a neurological deficit (Groot, Abelsohn & Moore, 2014; Walter, 2016). According to Groot et al. (2014), heat exhaustion is more frequent than heat stroke, but fortunately not as severe. This does not mean you should be less diligent with your assessment, monitoring, and treatment. Patients with heat exhaustion might also display signs or symptoms of dizziness, feeling thirsty, general weakness, a headache, tachycardia, oliguria, malaise, and possibly a mild fever, however, can progress into heat stroke if intervention is not taken (Gopinath, 2018; Walter, 2016). A thorough physical assessment is critical when it comes to differentiating the two injuries and ultimately, the treatment that will most benefit your patient.

Heat Stroke Heat Exhaustion
A core temperature above 40 degrees Celsius (104 degrees Fahrenheit)

 

A core temperature of less than than 40 degrees Celsius (104 degrees Fahrenheit)

 

AMS or neurological deficits

 

Dizziness, agitation
Warm, dry skin or sweating

 

Hot, flushed skin, and sweating
Tachypnea

 

Malaise, and general weakness
Tachycardia

 

Dizziness
Hypotension

 

Polydipsia
Lab Values

·       Creatinine levels >1.2 mg/dl

·       Increased aspartate aminotransferase (AST)

·       Increased alanine aminotransferase (ALT)

·       Increased Creatine Kinase (CK)

Oliguria

(Hifumi et al., 2018; Medicine, 2016; Epstein & Yanovich, 2019)

 

 

 At-Risk Populations

At-risk populations are those who are exposed to increased temperatures, but there are populations who are more vulnerable and when we assess should have a higher level of suspicion for a heat-related injury, one example is a heatwave that impacted Europe in 2003 which contributed to approximately 30,000 deaths, the majority of the deaths were people living in urban areas (Laaidi et al., 2012). That means if you work in an urban area, you should always be thinking, heat-related injury, especially during warmer months with extended periods of excessive temperatures.

Populations at most considerable risk are children, older adults, people with chronic disease processes such as diabetes mellitus, cardiovascular compromise, renal processes, and neurological disorders (Groot et al., 2014). Also, as Groot et al. (2014) explains people taking medications with the prefix “anti” are also at risk, for instance, anticholinergics, antidepressants, antipsychotics, and antihistamines; also included in medications are sympathomimetics, diuretics, and medications that cause vomiting and diarrhea. However, it is also important to note that people with increased exposure to the outdoors, such as athletes, workers, and anyone who has been outside in the heat for an extended period is at risk (Groot et al., 2014).

Last, but certainly not least are those affected by socioeconomic factors, for example people living in top floor apartments or rooms, those without air-conditioning, the homeless, any person who may be living in transient situations, and as mentioned earlier, people living in urban areas (Groot et al., 2014; Semenza, et al., 1996, (Kilbourne et al., 1992). As stated, noting the patient’s social circumstance during your initial physical assessment and patient care report can be pivotal when determining how to proceed with treatment and prevention of further heat-related injuries.

Management

Your priority in either situation is to manage your patient’s ABC’s and move them to a cooler area as quickly as possible (Wasserman, 2019). Once in a shaded or cool location, work to decrease the patients core temperature by removing clothing,  then using a fan (evaporation), wiping them with a cool washrag, wrapping the patient in a damp cool sheet (conduction), administer cooled intravenous fluids, place ice packs to the groin, neck, or axilla, and the use of immersion tanks, be careful using this method in your elderly patients (conduction) (Gopinath, 2018; Wasserman, 2019; Epstein & Yanovich, 2019). Work with what you have, like the back of an air-conditioned ambulance or a helicopter.

Be mindful to not “overshoot” (36 degrees Celsius or 96.8 degrees Fahrenheit) and cause your patient further complications (Wasserman, 2019). Measuring temperature is difficult when you do not have access to rectal, esophageal, or bladder probes; these are the most accurate means of measuring temperature (Ganio et al., 2009). The goal is to protect neurological function, and if shivering is induced, there is a chance to cause more harm than good to be vigilant and always monitor your patient for changes (Walter, 2016).

If accessible, place your patient on a cardiac monitor, and look for signs of tachycardia and tachypnea, monitor blood pressures for signs of hypotension; in at least one case study a young military patient showed signs of tachypnea and tachycardia which might be an objective sign of further complications for those of us in the field (Atar, 2003). However, it will help guide your treatment and assist you with concomitant findings

Unfortunately, the data supporting the use of vasoactive medications was controversial. My research found several articles that showed increased mortality rates associated with vasoactive medications. However, in one review, the authors supported the used of these medications, specifically, epinephrine, dopamine, and norepinephrine (Medicine, 2016; Epstein & Yanovich, 2019). In the previously mentioned review also suggested were the use of antiarrhythmics such as lidocaine and amiodarone. However, this was not supported by more recent articles, for example, Hifumi et al. (2018) who do not believe there is conclusive evidence to support the use of these medications.

Transporting these patients to a hospital is critical, and remember to give the receiving staff of your initial findings, to include the mental status and any changes that may have occurred during transport. If you had a temperature provide them with this information but be sure to mention how it was obtained, we do not want to mislead the staff into thinking the temperature is lower or higher than it actually is if we checked a forehead temperature in the field, which is far less accurate than a rectal temperature (Ganio et al., 2009).  Also, provide the receiving facility with any other information that might assist them with making a diagnosis and treating this patient appropriately.

Remember, HRIs are serious and detrimental to our overall well-being, and any patient suffering from it is at risk for long-term health consequences if not acted upon quickly. Below are a breakdown treatments for heat exhaustion and heatstroke. This bulleted list will also include interventions for you to look through if time is short:

Treatments for heat exhaustion and heat stroke:

  • ABC’s
  • Move the patient into a shaded location
  • Remove clothing
  • Lay the patient flat
  • Obtain temperature, rectally if feasible
  • Cool patient to no less than 38.9 degrees Celsius (102.2 degrees Fahrenheit) with evaporation or conduction, remember to use the tools you have readily available
  • Monitor mental status
  • Monitor vital signs
    • pulse oximetry
    • blood pressure
    • electrocardiography (ECG)
    • temperatures
  • Monitor urine output
  • Monitor for shivering
  • Treat seizures with benzodiazepines
  • Consider fluids if needed
  • If available monitor lab values, for instance, arterial blood gasses CK, creatine, and serum calcium.
  • Transport to the closest facility capable of managing this patient(Gopinath, 2018; Hifumi, Kondo, Shimizu, & Miyake, 2018; Epstein & Yanovich, 2019)

Always consider differential diagnoses such as but not limited to seizures, hypotension, adult respiratory distress syndrome, meningitis, drug intoxication, and renal failure; never assume your patient is going to be okay because he or she does not meet all of the criteria in this list (Gopinath, 2018, Epstein & Yanovich, 2019). We must be persistent and look for signs of deterioration or change; vigilance is critical, and being an astute clinician is critical.

Summary

It is summer, and the weather is expected to only get warmer over the next several decades (Seltenric, 2015; Epstein & Yanovich, 2019). Which means we need to be on our toes when it comes to the management of heat-related injuries like heat stroke. From 1999-2010, 8,081 deaths were associated with heat-related injuries in the United States, not a huge number, but when you consider that a majority of these deaths are entirely preventable it is shocking (CDC, n.d.; Groot et al., 2014). That said, it is crucial that we as, EMS,  HEMS, and critical care understand the symptomology and the sequelae of processes that can occur from HRI and in the primary and advanced management of heatstroke and heat exhaustion.

Focus on symptoms, remember the significant difference between someone with heat stroke and heat exhaustion is that he or she will present with an altered mental status (Groot et al., 2014; Kilbourne et al.,1992; Hifumi et al., 2018). Your primary focus should always be to manage the patients ABCs first, but quickly proceed to move them into the shade, and cooling them with whatever tools you have at your disposal. Remember to keep them from shivering so monitoring him or her is essential, use a cardiac monitor, your blood pressure cuff, and the most accurate temperature monitoring device available.

Finally, transport this individual to the nearest hospital that is capable of treatment. Make sure you are clear and concise with your report and give the staff the initial findings, to include your patients mental status, blood pressure, temperature (if available), and possibly urine output, as well as interventions you have performed throughout transport. The staff at the receiving facility will be better equipped with more information, remember that what you do not tell them they may never know. Also, in closing, thank you and remember to protect yourself, without you on the frontlines, there is no one to manage these patients, so hydrate and stay cool.


Atar, S. (2003). Transient cardiac dysfunction and pulmonary edema in exertional heat stroke. Military Medicine, 168, 671-673.

Centers for Disease Control and Prevention. (2018). The National Insitute for Occupational Safety and Health (NIOSH). Retrieved from Heat related illness: https://www.cdc.gov/niosh/topics/heatstress/heatrelillness.html

Centers for Disease Control and Prevention. (n.d.). Heat-related illness. Retrieved 2019, from CDC.gov: https://www.cdc.gov/pictureofamerica/pdfs/picture_of_america_heat-related_illness.pdf

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Laaidi, K., Zeghnoun, A., Dousset, B., Bretin, P., Vandentorren, S., Giraudet, E., & Beaudeau, P. (2012). The impact of heat islands on mortality in Paris during the August 2003 heat wave. Environmental Health Perspective, 120(2), 254-259.

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Wasserman, D. D. (2019). Cooling techniques for the hyperthermia.Treasure Island: StatPearls Publishing.

 

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