Metabolic correlates in infants and children during anaesthesia and surgery

In 58 infants and children with body weights between 2.8 and 20.5 kg carbon dioxide production (VCO2 ml min-1) was measured during halothane anaesthesia for minor surgical procedures. In 22 cases measurements were made during both spontaneous and controlled ventilation during the same operation. A non-rebreathing circuit was used. Expired ventilation volume was measured with a dry gas meter and expired gas collected during 3-5 min in a Douglas bag. The carbon dioxide fraction of exhaled gas was determined with a sampling Gould capnograph. A respiratory quotient (RQ) of 0.8 was used to calculate oxygen consumption (VO2 ml min-1). During spontaneous breathing, regression analysis of the relationship between VCO2 and kg and between VO2 and kg showed high intercepts while corresponding relations to kg3/4 revealed an almost direct proportionality. Thus, VCO2 and VO2 ought to be related to body weight in kg3/4 in spontaneously breathing children. The mean value (+/- 1 s.d.) for VCO2 was 11.4 +/- 3.1 ml kg-3/4 and for VO2 14.2 +/- 3.9 ml kg-3/4. During controlled ventilation, the relationship between kg b.w. showed for VCO2 as well as for VO2 an almost direct proportionality with a mean value (+/- 1 s.d.) for VCO2 of 6.3 +/- 1.6 ml min-1 kg-1 and for VO2 of 7.8 +/- 2.0 ml min-1 kg-1. Prediction of VO2 for infants and children of this size could be based upon 14 X kg3/4 during halothane anaesthesia and surgery.