Hyperthermia: Heat Stroke, Exhaustion, and Cramps

By admin On Sep 26, 2023

Ovid: 5-Minute Sports Medicine Consult, The

Christopher C. Trigger

Tanya J. Hagen

Basics

Description

Heat illness is the result of increased heat production and impaired heat dissipation.
Exertional heat illness is a continuum, but based on signs and symptoms can be divided into the following groups:
- Heat cramps
- Heat exhaustion
- Heat stroke

Epidemiology

Incidence

∼400 deaths per year can be attributed to all types of heat illness in the U.S.
Exertional heat stroke is the 3rd leading cause of death in athletes (1).

Prevalence

Football has been identified as the sport with the greatest number of heat-related fatalities.
From 1995–2005, 26 deaths were reported in high school, collegiate, and professional football due to heat stroke (1).

Risk Factors

Hot, humid weather
Dehydration
Sickle trait
Age (<15 yrs or >65 yrs)
Poorly trained and/or overweight athletes
Cumulative heat load from previous days' exposures
Improper attire (plastic suits)
Equipment (football pads/helmet)
Poor acclimatization
Medications:
- Dietary supplements (ie, ephedra, diet pills)
- Antihypertensives (ie, diuretics, beta-blockers, calcium channel blockers)
- Tricyclic antidepressants
- Monoamine oxidase inhibitors
- Antihistamines
- Amphetamines
- Illicit drugs (ie, cocaine, heroin, phencyclidine)
Concurrent illness (viral illness, skin disorders, cardiac disease)

General Prevention

Pre/post hydrate
Modify time, intensity, and exposure in hot, humid weather:
- Exercise in the early morning or evening.
- Limit sun exposure if possible.
- Remove unnecessary equipment and/or clothing.
Heat acclimatization (usually takes 10–14 days) (2)[C]
Increase electrolyte intake, mainly sodium (Na), using sports drinks.

Etiology

Heat dissipation occurs via 4 processes (1,3):

Radiation is the direct release of heat from the body to the environment.
Conduction occurs with direct transfer of heat during contact with a cooler object.
Convection is when cooler air passes over the warmer exposed skin, lifting the heat away.
Evaporation through perspiration is the body's most effective way of eliminating heat, although limited when humidity is high.

Diagnosis

History

Heat cramps:
- Painful involuntary contractions of muscles, most commonly the calf, quadriceps, and abdomen
- Heat cramps are more commonly thought of as an electrolyte problem than a heat issue.
Heat exhaustion:
- Fatigue
- Shortness of breath
- Dizziness or syncope
- Nausea and vomiting
- Normal mental status
Heat stroke:
- CNS symptoms with the correct environmental conditions (hot and humid)
- Previous history of heat exhaustion

Physical Exam

Heat cramps:
- Normal temperature and vital signs
- Tense, tender, involuntary contraction of the muscle belly
Heat exhaustion:
- Normal or elevated core temperature but <40°C (104°F)
- Vital signs usually normal, but can be variable depending on severity
- Normal mental status
- Flushed skin
- Profuse sweating
- Cold, clammy skin
Heat stroke:
- Core (rectal) temperature >40°C (104°F) (2)[B]
- CNS disturbances (confusion, ataxia, irritability, coma)
- Tachycardic, tachypneic, and hypotensive
- Hot skin with or without sweating
- End organ damage/failure

Diagnostic Tests & Interpretation

Lab

Routine lab work typically unnecessary for minor heat illness, but depending on the clinical picture, you may need to check the following:

CBC
Basic metabolic panel
Urinalysis to detect myoglobin
Serum creatine kinase to evaluate for rhabdomyolysis
Toxicology screen
Cardiac enzymes
Liver function tests
Coagulation studies to evaluate disseminated intravascular coagulation

Diagnostic Procedures/Surgery

EKG: Consider in heat stroke to look for cardiac damage/dysfunction

P.311

Differential Diagnosis

Dehydration
Electrolyte abnormality
Cardiovascular disease
Exercise-associated collapse
CNS lesion
Thyroid dysfunction
Infection

Treatment

Acute treatment:
- Use basic or advanced cardiac life support for all unstable patients and transfer them to the nearest medical facility.
- Common theme in treating all heat illnesses is to lower the core temp to an acceptable (38°C) level as quickly as possible
Heat cramps (2,13):
- Rest
- Oral replacement of fluids and electrolytes (Na) using sports drinks (1)
- IV fluids if unable to tolerate by mouth
- Passive stretching and/or ice massage of the affected muscles
Heat exhaustion (1,2,3):
- More aggressive cooling techniques:
  - Move to cool environment.
  - Rest and remove excess clothing.
  - Apply ice bags to neck, axilla, and groin (2)[C].
- Place in supine position and elevate legs.
- Replacement of fluids and electrolytes
- IV fluids if unable to tolerate oral rehydration
Heat stroke (1,2,3):
- Support airway, breathing, and circulation.
- Rapid cooling of the patient is first line:
  - Cold/ice water immersion most rapid form of cooling (2)[A]
  - If immersion unavailable, place wet towels/sheets and ice bags to neck, axilla, and groin (1,2,3)[C]
- IV fluids

Danger Category	Apparent Temperature (°F)	Heat Syndrome
IV. Extreme danger	130°F or higher	Heat stroke highly likely with continued exposure
III. Danger	105–130°F	Heat cramps or heat exhaustion likely, and heat stroke possible with prolonged exposure and/or physical activity
II. Extreme caution	90–105°F	Heat stroke, heat cramps, and heat exhaustion possible with prolonged exposure and/or physical activity
I. Caution	80–90°F	Fatigue possible with prolonged exposure and/or physical activity

ED Treatment

Any person exhibiting signs of worsening heat illness, specifically those with mental status changes and a temperature >40°C, should be immediately cooled and transferred for improved monitoring and management.
Once in the emergency department, the patient will undergo similar cooling techniques as noted above.

Ongoing Care

Follow-Up Recommendations

Return to play recommendations (1,2):

Heat cramps [C]:
- May return immediately after symptoms resolve with rest and fluid replacement
- Depending on severity, may require 24 hr of relative rest
Heat exhaustion [C]:
- Immediate return not recommended
- Generally can return to activity within 24–48 hr
- Gradually increase intensity and volume of training
Heat stroke [B]:
- Consider at least 7 days of rest or until asymptomatic and lab values have normalized.
- Consider follow-up no later than 1 wk after event or even sooner based on severity of symptoms and lab abnormalities.
- When cleared, begin training in cool environment and acclimate to heat over a 2-wk period.
- Clear the athlete for full competition if heat tolerance exists after 2–4 wks of training.
- If athlete does not tolerate return to play progression or has recurrent heat illnesses, consider laboratory exercise-heat tolerance test.

Patient Education

Avoid risks listed above.
“Salty sweaters” may be at higher risk for heat cramps due to loss of Na; encourage increased salt intake with meals and hydration with electrolytes.

Complications

End organ failure
Seizures
Cardiovascular collapse
Acute respiratory distress syndrome
Liver failure
Acute renal failure
Rhabdomyolysis
Disseminated intravascular coagulation

References

1. Howe AS, Boden BP. Heat-related illness in athletes. Am J Sports Med. 2007;35:1384–1395.

2. Armstrong LE, Casa DJ, Millard-Stafford M, et al. Exertional heat illness during training and competition. Med Sci Sports Exerc. 2007;39:556–572.

3. Wexler RK. Evaluation and treatment of heat-related illnesses. Am Fam Physician. 2002;65:2307–2314.

Codes

ICD9

992.0 Heat stroke and sunstroke
992.1 Heat syncope
992.2 Heat cramps