Heat syncope is
fainting
Syncope, commonly known as fainting, or passing out, is a loss of consciousness and muscle strength characterized by a fast onset, short duration, and spontaneous recovery. It is caused by a decrease in blood flow to the brain, typically from ...
or dizziness as a result of overheating (''syncope'' is the medical term for fainting). It is a type of
heat illness
Heat illness is a spectrum of disorders due to increased body temperature. It can be caused by either environmental conditions or by exertion. It includes minor conditions such as heat cramps, heat syncope, and heat exhaustion as well as the mo ...
. The basic symptom of heat syncope is fainting, with or without
mental confusion
In medicine, confusion is the quality or state of being bewildered or unclear. The term "acute mental confusion" . Heat syncope is caused by peripheral vessel dilation, resulting in diminished blood flow to the brain and
dehydration
In physiology, dehydration is a lack of total body water, with an accompanying disruption of metabolic processes. It occurs when free water loss exceeds free water intake, usually due to exercise, disease, or high environmental temperature. Mil ...
.
Signs and symptoms
Faintness, dizziness, headache, increased pulse, restlessness, nausea, vomiting, pale/clammy skin, and brief loss of consciousness.
Causes
Heat syncope occurs in a warm environment when
blood pressure is lowered as the body dilates (widens)
arterioles
An arteriole is a small-diameter blood vessel in the microcirculation that extends and branches out from an artery and leads to capillaries.
Arterioles have muscular walls (usually only one to two layers of smooth muscle cells) and are the primar ...
(small
blood vessel
The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide away ...
s) in the skin to radiate heat. This condition occurs within five days of
heat acclimatization, before the blood volume expands.
[http://www.sportsci.org/encyc/drafts/Heat_acclimatization/heataccl.doc ] The result is less blood to the brain, causing light-headedness and
fainting
Syncope, commonly known as fainting, or passing out, is a loss of consciousness and muscle strength characterized by a fast onset, short duration, and spontaneous recovery. It is caused by a decrease in blood flow to the brain, typically from ...
when a person stands up quickly or stands for a long period of time. Those who perform strenuous work outside in warm climates are at particular risk.
Diagnosis
The diagnosis of heat syncope is done during a physical examination. During the physical exam the practitioner will test the blood pressure of the patient, and the pulse. If the patient is experiencing heat syncope the blood pressure will be low, and the pulse will be elevated. Observation of excess sweating will also be a key sign. Finally, the practitioner will ask questions figuring out the history of the patient's symptoms. If the patient developed symptoms while engaging in physical activity and high temperatures it will then be a true case of heat syncope.
Prevention
Physical activity in extremely hot weather should be avoided. If a person starts to experience over heating, and symptoms of heat syncope, they should move or be moved to a shaded or cool area. It is also recommended to avoid alcoholic beverages in hot weather, because they cause dehydration which may worsen symptoms. Finally, drinking plenty of water with
electrolytes is imperative when engaging in physical activity in hot weather.
Treatment
The basic treatment for heat syncope is like that for other types of fainting: the patient is positioned in a seating or
supine position
The supine position ( or ) means lying horizontally with the face and torso facing up, as opposed to the prone position, which is face down. When used in surgical procedures, it grants access to the peritoneal, thoracic and pericardium, pericardi ...
with legs raised. Water containing salt, or another drink containing electrolytes, is administered slowly, and the patient is moved to a cooler area, such as the shade.
The affected person should rest and recover, because heat syncope can lead to
heat stroke
Heat stroke or heatstroke, also known as sun stroke, is a severe heat illness that results in a body temperature greater than , along with red skin, headache, dizziness, and confusion. Sweating is generally present in exertional heatstroke, ...
or
heat exhaustion Heat exhaustion is a severe form of heat illness. It is a medical emergency. Heat exhaustion is caused by the loss of water and electrolytes through sweating.
The United States Department of Labor makes the following recommendation, "Heat illness ...
.
References
External links
{{Disorders of consciousness
Medical emergencies
Effects of external causes