Trial by Fire
Answer: D
This man presents in the spectrum of heat-related illness (HRI). First, a few common (milder) presentations of
HRI:
Heat rash (i.e. heat rash, “prickly rash”, miliaria) – seen in adults and children, caused by eccrine duct
obstruction; supportive care
Heat edema – doughy pitting edema of the extremities, caused by prolonged vasodilation, pooling of interstitial
fluid; consider heart failure and other etiologies, elevation, supportive care
Heat cramps – aching and weakness in symmetrical major muscle groups, mostly due to exertion and loss of
electrolytes
Heat tetany – hyperventilation (in this case, the human equivalent of ‘panting’), causing hyperventilatory
symptoms such as circumoral and extremity paresthesias, carpopedal spasm; evaluate volume status, supportive
care
Heat syncope – orthostasis from heat-related peripheral vasodilation and venous pooling; evaluate volume status, consider other causes of syncope, volume repletion, supportive care
Heat exhaustion – elevated core temperature (up to 104 F, 40 C), accompanied by any of the following:
● Fatigue and weakness
● Tachycardia
● Headache, dizziness
Note that volume depletion (dehydration) is not a prerequisite for heat exhaustion (or the more severe heat stroke) – HRI can occur in as little as 20 minutes of exposure to an inhospitable environment, especially in a non-acclimatized individuals (B).
The above presentations typically represent a milder form of the spectrum of HRI; vigilance should be applied during the treatment and observation phase for developing heat stroke. A common myth is that a normal mental status on presentation excludes heat stroke – patients may have an initial lucid interval, and decline
thereafter. Heat stroke connotes a significantly higher mortality (25-50% in some observational studies). Let’s review some important features of heat stroke to identify and evaluate in the patient at risk:
Non-exertional heat stroke typically occurs in poorly acclimatized individuals, those with comorbidities, psychiatric disorders, the elderly, and/or those taking diuretics or anticholinergics. This is “classic” heat
stroke.
Exertional heat stroke typically occurs in athletes or those in training – these are usually young, healthy
people exercising in the heat, and may or may not be dehydrated.
Heat stroke is a dangerous condition that can cause dysrhythmias, rhabdomyolysis, respiratory failure (ARDS), renal and hepatic dysfunction, seizures, coma, and death.
Treatment and evaluation for heat stroke are performed in a parallel manner.
Treatment
Rapid cooling – the patient is stripped of all clothes and sprayed down with water (evaporative cooling); ice packs to the major arteries accessible by the neck, axilla, and groin (conductive cooling); fans blowing over the patient’s skin (convective cooling); cool IV fluids (may put NS in ice bath for a few minutes prior to blousing – dilutional cooling); later cooling blankets and cool air/oxygen can be administered. In the case of cardiac arrest, invasive cooling measures such as chest tube placement with cold-water lavage have been reported. Continuous rectal temperature monitoring is recommended.
Seizures – in addition to cooling measures, treat with benzodiazepines
Dysrythmias – often resolve when the patient regains a more normal temperature: focus on rapid cooling. Similar
to hypothermia, pharmacotherapy and electricity have poor results in the hyperthermic patient. You may
observe tachydysrthymias such as SVT. Regardless of temperature, treat other dysrhythmias such as unstable
ventricular tachycardia and ventricular fibrillation as per usual with cardioversion.
Respiratory distress or declining mental status – be ready to establish a definitive airway.
Important don’ts: don’t perform cool gastric lavage (risk of aspiration and hyponatremia); and don’t give antipyretics (acetaminophen and other NSAIDs may exacerbate hepatic and renal dysfunction, and they do not
have an effect on heat-related illness, a “physical” problem of excess heat, rather than a “neurohormonal” excitation of the hypothalamus).
Evaluation
As you can see, heat stroke is a multi-organ dysfunction; be thorough in your investigation. Think of this as a systemic inflammatory response syndrome (SIRS). Strongly consider: CBC (platelets), chemistries (hyper/hypo-natremia/kalemia, renal failure, hypocalcemia), CK (rhabdomyolysis), PT/PTT (developing disseminated intravascular coagulation), UA (proteinuria, myoglobinuria), EKG (prolonged QT, transient Brugada-like
patterns, reversible demand ischemic changes), cardiac biomarkers, chest film (pulmonary edema, cardiogenic and non-cardiogenic).
Disposition
Patients on the mild end of the spectrum (e.g. heat cramps, heat syncope, heat exhaustion) who are improved and back to baseline after evaluation and treatment often do well as outpatients. Patients with heat stroke, however, must be stabilized rapidly and kept for ongoing treatment and further monitoring.
Now, with that as a background, a few more common myths about HRI:
● Although severe HRI can cause anhidrosis, it is more common to see those affected by HRI to continue to
sweat; that is, the presence of sweat does not rule-out severity of illness (A).
● Mental status changes (confusion, agitation, stupor) qualify the hyperthermic exposed patient for heat
stroke. However, as you can see, multiple organ systems may be involved, and mental status changes
may not be overtly present or may be subtle initially. Be prepared for a dynamic presentation.
● Individuals with a normal baseline temperature will shiver when exposed to cold. Hyperthermic
patients may not shiver (due to hypothalamic dysfunction). Continue to cool through shivering in the
patient with heat stroke: the goal is rapid cooling, and although shivering can be uncomfortable, it may be a
necessary side effect until a normal temperature is reached.
References
Becker JA, Stewart LK. Heat-related illness. Am Fam Physician. 2011;83(11):1325-1330.
Bouchama A, Dehbi M, Chaves-Carballo E. Cooling and hemodynamic management in heatstroke: practical recommendations. Crit Care. 2007; 11:R54.
Carter R, Cheuvront SN, Williams JO et al. Epidemiology of Hospitalizations and Deaths from Heat Illness in Soldiers. Med Sci Sports Exerc. 2005;37(8):1338-44.
Coris EE, Ramirez AM, Van Durme DJ. Heat Illness in Athletes: The Dangerous Combination of Heat, Humidity and Exercise. Sports Med. 2004; 34 (1): 9-16.
This man presents in the spectrum of heat-related illness (HRI). First, a few common (milder) presentations of
HRI:
Heat rash (i.e. heat rash, “prickly rash”, miliaria) – seen in adults and children, caused by eccrine duct
obstruction; supportive care
Heat edema – doughy pitting edema of the extremities, caused by prolonged vasodilation, pooling of interstitial
fluid; consider heart failure and other etiologies, elevation, supportive care
Heat cramps – aching and weakness in symmetrical major muscle groups, mostly due to exertion and loss of
electrolytes
Heat tetany – hyperventilation (in this case, the human equivalent of ‘panting’), causing hyperventilatory
symptoms such as circumoral and extremity paresthesias, carpopedal spasm; evaluate volume status, supportive
care
Heat syncope – orthostasis from heat-related peripheral vasodilation and venous pooling; evaluate volume status, consider other causes of syncope, volume repletion, supportive care
Heat exhaustion – elevated core temperature (up to 104 F, 40 C), accompanied by any of the following:
● Fatigue and weakness
● Tachycardia
● Headache, dizziness
Note that volume depletion (dehydration) is not a prerequisite for heat exhaustion (or the more severe heat stroke) – HRI can occur in as little as 20 minutes of exposure to an inhospitable environment, especially in a non-acclimatized individuals (B).
The above presentations typically represent a milder form of the spectrum of HRI; vigilance should be applied during the treatment and observation phase for developing heat stroke. A common myth is that a normal mental status on presentation excludes heat stroke – patients may have an initial lucid interval, and decline
thereafter. Heat stroke connotes a significantly higher mortality (25-50% in some observational studies). Let’s review some important features of heat stroke to identify and evaluate in the patient at risk:
Non-exertional heat stroke typically occurs in poorly acclimatized individuals, those with comorbidities, psychiatric disorders, the elderly, and/or those taking diuretics or anticholinergics. This is “classic” heat
stroke.
Exertional heat stroke typically occurs in athletes or those in training – these are usually young, healthy
people exercising in the heat, and may or may not be dehydrated.
Heat stroke is a dangerous condition that can cause dysrhythmias, rhabdomyolysis, respiratory failure (ARDS), renal and hepatic dysfunction, seizures, coma, and death.
Treatment and evaluation for heat stroke are performed in a parallel manner.
Treatment
Rapid cooling – the patient is stripped of all clothes and sprayed down with water (evaporative cooling); ice packs to the major arteries accessible by the neck, axilla, and groin (conductive cooling); fans blowing over the patient’s skin (convective cooling); cool IV fluids (may put NS in ice bath for a few minutes prior to blousing – dilutional cooling); later cooling blankets and cool air/oxygen can be administered. In the case of cardiac arrest, invasive cooling measures such as chest tube placement with cold-water lavage have been reported. Continuous rectal temperature monitoring is recommended.
Seizures – in addition to cooling measures, treat with benzodiazepines
Dysrythmias – often resolve when the patient regains a more normal temperature: focus on rapid cooling. Similar
to hypothermia, pharmacotherapy and electricity have poor results in the hyperthermic patient. You may
observe tachydysrthymias such as SVT. Regardless of temperature, treat other dysrhythmias such as unstable
ventricular tachycardia and ventricular fibrillation as per usual with cardioversion.
Respiratory distress or declining mental status – be ready to establish a definitive airway.
Important don’ts: don’t perform cool gastric lavage (risk of aspiration and hyponatremia); and don’t give antipyretics (acetaminophen and other NSAIDs may exacerbate hepatic and renal dysfunction, and they do not
have an effect on heat-related illness, a “physical” problem of excess heat, rather than a “neurohormonal” excitation of the hypothalamus).
Evaluation
As you can see, heat stroke is a multi-organ dysfunction; be thorough in your investigation. Think of this as a systemic inflammatory response syndrome (SIRS). Strongly consider: CBC (platelets), chemistries (hyper/hypo-natremia/kalemia, renal failure, hypocalcemia), CK (rhabdomyolysis), PT/PTT (developing disseminated intravascular coagulation), UA (proteinuria, myoglobinuria), EKG (prolonged QT, transient Brugada-like
patterns, reversible demand ischemic changes), cardiac biomarkers, chest film (pulmonary edema, cardiogenic and non-cardiogenic).
Disposition
Patients on the mild end of the spectrum (e.g. heat cramps, heat syncope, heat exhaustion) who are improved and back to baseline after evaluation and treatment often do well as outpatients. Patients with heat stroke, however, must be stabilized rapidly and kept for ongoing treatment and further monitoring.
Now, with that as a background, a few more common myths about HRI:
● Although severe HRI can cause anhidrosis, it is more common to see those affected by HRI to continue to
sweat; that is, the presence of sweat does not rule-out severity of illness (A).
● Mental status changes (confusion, agitation, stupor) qualify the hyperthermic exposed patient for heat
stroke. However, as you can see, multiple organ systems may be involved, and mental status changes
may not be overtly present or may be subtle initially. Be prepared for a dynamic presentation.
● Individuals with a normal baseline temperature will shiver when exposed to cold. Hyperthermic
patients may not shiver (due to hypothalamic dysfunction). Continue to cool through shivering in the
patient with heat stroke: the goal is rapid cooling, and although shivering can be uncomfortable, it may be a
necessary side effect until a normal temperature is reached.
References
Becker JA, Stewart LK. Heat-related illness. Am Fam Physician. 2011;83(11):1325-1330.
Bouchama A, Dehbi M, Chaves-Carballo E. Cooling and hemodynamic management in heatstroke: practical recommendations. Crit Care. 2007; 11:R54.
Carter R, Cheuvront SN, Williams JO et al. Epidemiology of Hospitalizations and Deaths from Heat Illness in Soldiers. Med Sci Sports Exerc. 2005;37(8):1338-44.
Coris EE, Ramirez AM, Van Durme DJ. Heat Illness in Athletes: The Dangerous Combination of Heat, Humidity and Exercise. Sports Med. 2004; 34 (1): 9-16.