Peripheral vasodilation is one of the first mechanisms the body will employ in an effort to maintain a homeostatic core temperature while in an environment with high ambient temperature. Vasodilatation increases blood flow to the extremities and brings blood closer to the skin’s surface so that heat may be dissipated through the evaporative effects of sweat and direct radiation of heat energy from the body. As a result of this increase in blood flow the intravascular hydrostatic pressure increases. Additionally, with vasodilation comes increased vascular permeability (Rowell, 1983).
The combination of increased permeability and increased hydrostatic pressure within the circulatory system results in a net movement of fluid into the interstitium. When the lymph system is unable to clear this excess fluid faster than it is accumulating, third spacing of intravascular fluid occurs into the surrounding soft tissues. This pooling of fluid is edema (Howe, 2007). Common risk factors for the development of heat edema include:
– Lack of acclimatization
– Underlying cardiovascular disease
– Diabetes mellitus
– Underlying kidney disease
– Elderly age
– Prolonged standing or ambulation
CLINICAL PRESENTATION & DIAGNOSIS
Heat edema manifests as dependent soft tissue swelling. Typically, this occurs in the lower extremities, but any dependent area may be affected. Patients are often elderly and lack proper acclimatization. Physical exam will reveal symmetrical dependent pitting edema. With simple heat edema there should be no impairment in function and no systemic symptoms such as shortness of breath, chest pain, or dizziness. Presence of any additional symptoms beyond simple edema should prompt the evaluating physician to seek other causes, with particular emphasis on cardiopulmonary assessment (Howe, 2007).
– Congestive heart failure
– Liver disease
– Kidney disease
– Deep venous thrombosis
– Peripheral vascular disease
Heat edema is self-limiting and will resolve with proper acclimatization. Supportive care involves moving the patient to an area of lower temperature if possible and elevation of the affected area to promote fluid drainage. Additionally, compression sleeves will help promote drainage and prevent reaccumulation of fluid (Howe, 2007).
Dr. Erik Leci and Dr. Graham Briscoe (February 16, 2020 – ND)
Howe. (2007). Heat-Related Illness in Athletes. American Journal of Sport Medicine , 1384 -1395.
Rowell. (1983). Cardiovascular aspects of human thermoregulation. Circulation Research, 52:367–9.