Metabolic disturbances of hypothermia

Abstract

Thermal balance Human body temperature is normally maintained within the range of 36.0+0.7~ by a balance between heat production and heat loss. The thermoregulatory centre receives an input from superficial and deep receptors located in several parts of the body, such as skin, mucous membranes of the mouth, abdominal and thoracic viscera, and spinal cord. Thermoregulation involves the integration of three areas of the central nervous thermosensitive neurones. These are a rudimentary control in the spinal cord, a secondary control within the reticular formation of the medulla, and a primary control located in the preoptic anterior hypothalamus. These centres integrate the peripheral and central temperature input and are able to establish a 'set point' and detect any discrepancy between this and the core temperature. The set point is influenced by age, circadian rhythm, exercise, hormones, neurotransmitters, pyrogens, cancer, trauma and drugs. The efferent reflexes generate, conserve or dissipate heat, depending on whether the core temperature is below or above the set point. Figure 1 shows how body temperature can be efficiently maintained within normal limits. In this individual the set point was 37. I~ a temperature at which