STUDY OF THE SAFE THRESHOLD OF APNEIC PERIOD IN CHILDREN DURING ANESTHESIA INDUCTION

Study Objectives: (1) To investigate changes in arterial oxygen satura tion via pulse oximeter (SpO(2)) during apnea and after reinstitution of manual ventilation at SpO(2) of 95% or 90% following rapid sequence induction of anesthesia in children after 2-minute preoxygenation; (2 ) to determine whether the setting of a safe threshold of apneic perio d to an SpO(2) of 95% is appropriate in children during anesthetic ind uction; and (3) to evaluate the influences of age, body weight, and he ight on the time from the start of apnea to SpO(2) of 95%. Design: A c linical study of random design and comparison among groups. Setting: O perating room of a plastic surgery hospital of the Chinese Academy of Medical Sciences and Peking Union Medical College. Patients: 152 infan ts and children, ASA physical status I, aged 3 months to 12 years, sch eduled for elective plastic surgery. Interventions: Patients were divi ded into three age groups: Group 1-infants 3 months to 1 year (n = 39) ; Group 2-children 1 to 3 years (n = 41); and Group 3-children 3 to 12 years (n = 72). Patients in each age group were randomly allocated ag ain to Subgroups A and B. After a 2-minute preoxygenation, anesthesia was induced with thiopental 5 mg/kg, fentanyl 5 mu g/kg, and suxametho nium 1.5 mg/kg. Patients were manually ventilated when SpO(2) decrease d to 90% in Subgroups A and 95% in Subgroups B, respectively, during a pnea. Measurements and Main Results: SpO(2) was measured continuously with a Datex pulse oximeter applied to the right index finger. During apnea, the times for SpO(2) to decrease to 99% (T-99) and 95% (T-95) i n all children, and 90% (T-90) in Subgroups A were recorded. The time for SpO(2) to decrease from 95% to 90% (T-95-90) in Subgroups A was al so measured. After reinstitution of manual ventilation, the time when SpO(2) continued to decrease (T-1) and the time from the end of apnea to recovery of SpO(2) baseline (T-2) were determined. In addition, the lowest value of SpO(2) after apnea was also recorded. The results sho wed that younger children were more susceptible than older children to the risk of hypoxemia during apnea. There were significant difference s in T-99, T-95, T-90, and T-95-90 between the three age groups. T-1 a nd T-2 were significantly longer in Group 3 than in Groups 1 and 2. Th ere were significantly differences in the lowest values of SpO(2) foll owing apnea among the three Subgroups A and between Subgroups A and B of each age group. During apnea, heart rate decreased gradually as SpO (2) decreased, showing a significant decrease at SpO(2) of 95%. Bradyc ardia was found in three children in Subgroups A. The apnea time to Sp O(2) to 95% correlated well with age, weight, and height by linear reg ression analysis. Conclusions: The safe threshold of an apneic period setting to an SpO(2) of. 95% was appropriate in children anesthesia in duction. Despite the same duration of pre-oxygenation, younger childre n were more susceptible than older ones to the risk of hypoxemia durin g apnea. The apnea time to SpO(2) of 95% correlated with age, body wei ght, and height using linear regression analysis. (C) 1996 by Elsevier Science Inc.