This is supported by an increased respiratory rate. Tidal volume and dead space are equivalent to adults on a per kilogram basis. Children desaturate rapidly because of increased utilization of oxygen per kilogram , and because their FRC is decreased under anesthesia. FRC decreases under anesthesia because of small alveoli, and a very compliant chest wall. Both of these things lead to increased atelectasis.
Pediatric patients lose heat to the environment more readily than adults.
This is due to an increased surface area per kilogram. This is compounded by cold intravenous fluids, dry anesthetic gases, and wound exposure. Hypothermia is a serious problem which can result in delayed awakening, cardiac irritability and respiratory depression. Infants cannot shiver, but must metabolize brown fat to maintain temperature. Half is replaced in the first hour of surgery, one quarter in the second hour, and the remaining quarter in the third hour 3.