Wilderness Medicine

Heat Injuries: Edema, Tetany, Syncope, Heat Rash

Heat Edema

1. Background
   • Definition
     • Minor swelling of hands and feet developing within first few days upon arrival in a hot environment
   • Pathophysiology
     • Result of cutaneous vasodilation
   • Diagnostics
     • Edema involving hands, feet and possibly ankles
2. Treatment
   • Self-limited condition
   • Elevate extremities

Heat Tetany

1. Background
   • Definition
     • Hyperventilation as a result of heat stress
   • Pathophysiology
     • Stress response to extreme heat
   • Diagnostics
     • Hyperventilation, respiratory alkalosis
     • Paresthesias
       • Circumoral
       • Extremities
     • Muscle spasms
       • Carpopedal spasm
     • Respiratory difficulty
     • Labs
       • Consider creatine kinase to rule out rhabdomyolysis
2. Treatment
   • Hydration
     • Isotonic oral solutions
     • IV fluids
   • Rest in cool place
   • Encourage slow deep breathing
   • Avoidance of further exertion

Heat Syncope

1. Background
   • Definition
     • Hypotension and peripheral venous pooling in early heat response
   • Pathophysiology
     • Caused by decreased vasomotor tone
   • Diagnostics
     • Dizziness
     • Nausea, vomiting
     • Decreased vasomotor tone
     • Labs
       • Consider creatine kinase to rule out rhabdomyolysis
2. Treatment
   • Hydration
     • Isotonic oral solutions
     • IV fluids
   • Rest in cool place

Heat Rash

1. Background
   • Definition
     • Acute inflammatory erythematous rash
     • Also known as "Prickly heat", Miliaria rubra (View image)
   • Pathophysiology
     • Blockage of sweat pores ⇒ pressure ⇒ rupture ⇒ pruritic vesicles ⇒ inflammation
   • Diagnostics
     • Erythematous blanching rash
     • May be pruritic
2. Treatment
   • Rest in cool place
   • Avoid sweating
   • Keep skin cool and dry
   • Resolves spontaneously in a matter of days
   • Consider
     • Antihistamines
     • Steroid creams

Related Topics

• Heat cramps
• Heat exhaustion
• Heat stroke

References

1. Cuddy JS, Ruby BC. High work output combined with high ambient temperatures caused heat exhaustion in a wildland firefighter despite high fluid intake. Wilderness Environ Med. 2011;22(2):122-125
2. Lewis AM. Emergency: heatstroke in older adults. In this population it's a short step from heat exhaustion. Am J Nurs. 2007;107(6):52-56
3. (NATA) NATA, Institute KS. Tips for exercising safely in the heat: steer clear of heat cramps, heat exhaustion, and heat stroke with key information. NASN Sch Nurse. 2011;26(4):230-232
4. Auerback PS, et al (eds). Wilderness Medicine: Expert Consult, Elsevier-Mosby:Philadelphia, PA, 2012;Part 2
5. Howe AS, Boden BP. Heat-related illness in athletes. The American Journal of Sports Medicine. 2007;35(8):1384–1395
6. Becker JA, Stewart LK. Heat-related illness. American Family Physician. 2011;83(11):1325–1330
7. Gilchrist J, Haileyesus M, Murphy M, Comstock R, Collins C, McIlvain N, et al. Morbidity and Mortality Weekly Report. 32. Vol. 59. Atlanta: Center for Disease Control; 2010. Aug 20
8. Mahant S. The evaluation and management of heat injuries in an intensive care unit. Indian J Crit Care Med. 2015 Aug;19(8):479-83
9. Gauer R, Meyers BK. Heat-Related Illnesses. Am Fam Physician. 2019 Apr 15;99(8):482-489. PMID: 30990296

Contributor(s)

1. Ballarin, Daniel, MD

Updated/Reviewed: January 2023