Inadvertent Hypothermia· under General Anesthesia in Geriatric patients: Study on Hemodynamic, Stress, and Metabolic Responses

Abstract

At the other end of the scale, ice crystals form in mammalian cells at -1°C and physical disruption of cells occurs. (4) ·In intact animals, vital organ function becomes critically impaired at internal temperature much higher than freezing; for example consciousness is lost in man at 30°C and death often occurs at temperatures less than 25°C as a result of ventricular fibrillation.

Accurate maintenance of the internal temperature at a value close to the optimum for enzymatic activity provides many benefits, including a constant high rate of metabolism, rapid nervous conduction and muscular contraction and decreased viscosity of blood. < 4>

HOMEOTHERMY:

Is defined by thermal physiology commissiOn of the international union of physiological sciences as "a pattern of temperature regulation in which cyclic variation in core temperature is maintained within a narrow limit of ±0.2°C despite much large variations in ambient temperature." (S)

Only mammals and birds conform to this definition; however, all other vertebrates exhibit some degree of thermal regulation,

maintained usually by behavioral responses.( 6

Homeothermy involves

sensing body temperature and appropriately driving the mechanisms controlling heat loss and gain so as to maintain a normal value for temperature thus thermoregulation is a closed -loop system. < 6