The temperature of the human body is maintained within narrow limits using two parallel processes – physiological temperature regulation and behavioral reactions. Behavioral temperature regulation includes staying in the shade, reducing the intensity or stopping of activities, and removing clothing and equipment, if any. Physiological regulation of the body is mainly determined by the hypothalamic thermoregulatory center.
Exposure to high environmental temperatures is a stress for the human body. The organism tries to compensate for the adverse impact, but this, in turn, leads to a load on the physiological adaptation mechanisms. In combination with the impact of factors such as dehydration, fatigue, and intense physical activity are prerequisites for the development of heat injuries.
An increase in body temperature by 2 °C puts a significant strain on the cardiovascular system and sharply reduces work capacity. Persons with a low degree of physical training have a reduced tolerance when exposed to high environmental temperatures. Physically trained people have an increased cardiovascular reserve, which covers to a significant extent the increased need for blood circulation in conditions of heat stress.
The thermoregulatory capacity and tolerance to the development of thermal injuries decreases with advancing age. Cardiovascular diseases, manifested by congestive heart failure, are adversely affected by the effects of increased environmental temperature, due to the increased deposition of blood in the skin blood vessels and the strengthening of stasis.
Various skin diseases, including sunburn, impair the activity of thermoregulatory mechanisms and thereby increase the risk of developing thermal injuries.
Some medications also affect thermoregulatory mechanisms. Sedative medications and narcotic analgesics impair memory function, which in turn leads to impaired judgment and reduced ability to make sound decisions during heat exposure.
Some medications affect thermoregulation by reducing sweating – for example, atropine, antihistamines, and tricyclic antidepressants. Others have an adverse effect by increasing heat production – thyroid hormones, and ephedrine. Beta-blockers have a reducing effect on blood flow to the skin, and ACE inhibitors reduce the feeling of thirst and thus fluid intake.
High air humidity makes it difficult for sweat to evaporate and this makes it difficult for the body to give off heat. Such conditions exist in the jungles, where heat injuries can occur at not-so-high temperatures, but with air humidity reaching 100%. Thus, the risk of heat injury at the same air temperature is greater in jungles than in deserts.
Perceptible thermal acclimatization is achieved in a period of 3 to 5 days, but it takes 7 to 14 days for its full development.
Exposure to a high-temperature environment, without significant physical exertion, leads to only partial acclimatization of the occupants, enough to endure in such an environment without being able to perform additional physical activity. In parallel, dehydration reduces the thermoregulatory advantages achieved in the acclimatization process and should not be allowed during this period.
Hydration is important both for maintaining circulating blood volume and for efficient sweating. Food itself is also a source of water for the body, providing approximately 10% of the required amount. In addition, food provides the import of mineral substances and salts, necessary to retain fluids in the body, a large part of which is lost in the process of sweating.
Bibliography:
1. Damage caused by heat, E. Taneva
2. TB MED 507/ NAVMED P-5052-5/ AFP 160-1. Prevention, treatment and control of heat injury
The material is informative and cannot replace consultation with a doctor. Before starting treatment, you must consult a doctor.
