AGE AND THE ONSET OF DESATURATION IN APNEIC CHILDREN

Most patients undergoing general anaesthesia are apnoeic during laryng oscopy and tracheal intubation. This study determined the lime until t he onset of desaturation following preoxygenation in apnoeic infants, children, and adolescents. Fifty ASA physical status I patients, 2 day s to 18 yr of age, were studied. The patients were stratified into one of five groups according to age: Group I, 0-6 mo; Group II, 7-23 mo; Group III, 2-5 yr; Group IV 6-10 yr; and Group V, 11-18 yr. Following induction of anaesthesia with halothane via mask or intravenous barbit urates the ability of the anaesthetist to ventilate the lungs via the mask was ascertained and paralysis was accomplished with vecuronium 0. 1 mg . kg(-1). Manual mask ventilation was maintained with oxygen and halothane. When end-tidal N-2 decreased below 3% (minimum time two min utes), the face mask was removed. The time between the removal of the face mask and a decrease in oxygen saturation (SpO(2)) from 99-100% to 90% was measured. Manual ventilation was then resumed and the trachea intubated. Desaturation started earlier in infants than in two- to fi ve-year-old children (96.5 +/- 12.7 sec vs 160.4 +/- 30.7 sec, P < 0.0 001). Children became desaturated faster than adolescents (160.4 +/- 3 0.7 vs 382.4 +/- 79.9 sec, P < 0.0001). The time required to reach 90% saturation correlated well with age by linear regression analysis (r( 2) = 0.88, P < 0.0001). We conclude that the time to onset of desatura tion following pre-oxygenation with mask ventilation increases with ag e in healthy apnoeic children. Adolescents can tolerate apnoea for lon ger than children, and infants exhibit desaturation faster than childr en.