Thermal environment

Surgery seriously stresses the pediatric patient; thus, he or she may have difficulty maintaining a normal body temperature. The integrity of the skin is disturbed in surgery so that the interior and exterior of the body are exposed to an unnatural environment. The thermoregulatory centers are less responsive due to the anesthetic agents. Vasodilation is common with many anesthetic agents, thus precipitating hypothermia. By itself, hypothermia depresses body activity and reduces the need for oxygen. Uncontrolled depression may be fatal, and the rebound shivering that can occur in the PACU may increase the oxygen consumption by 400%.

Shivering can increase oxygen consumption by 400%!

Hyperthermia occurs in surgery as does hypothermia, and both may cause increased metabolism and increased oxygen demand. Infants are prone to hypothermia, whereas the older pediatric patient is more likely to develop hyperthermia. The newborn has a body mass that is 5% of the adult's and has a body surfacd area of 15% of an adult's; thus, the newborn has a greater surface area for potential heat loss. Also, the infant's subcutaneous fat is thin, which results in a 400% increase in core conductance.(Balan) The infant has an immature hypothalamic center and a higher metabolic rate than an adult, thus further increasing the chance of hypothermia. The older child is more likely to use shivering as a means of increasing temperature than the infant. The infant is capable of shivering, but it is not an effective mechanism of heat production at that age. The infant therefore is more likely to use nonshivering thermogenesis, that is, metabolism of brown adipose tissue. This brown fat is found in the scapular region, the mediastinum, around the kidneys, adrenal glands, and axilla, and in the muscles and blood vessels of the neck. Nonshivering thermogenesis is triggered by cold stress and results in heat production within these tissues and the transfer of heat to surrounding circulation. Oxygen requirements may be increased three times the normal rate with this method. Once the brown fat is utilized by the infant, it cannot be replenished.