Study of the safe threshold of apneic period in children during anesthesia induction

Abstract

Study Objectives: (1) To investigate changes in arterial oxygen saturation 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 period to an SpO 2 of 95% is appropriate in children during anesthetic induction; and (3) to evaluate the influences of age, body weight, and height on the time from the start of apnea to SpO 2 of 95%. Design: A clinical study of random design and comparison among groups. Setting: Operating room of a plastic surgery hospital of the Chinese Academy of Medical Sciences and Peking Union Medical College. Patients: 152 infants and children, ASA physical status I, aged 3 months to 12 years, scheduled for elective plastic surgery. Interventions: Patients were divided 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 again to Subgroups A and B. After a 2-minute preoxygenation, anesthesia was induced with thiopental 5 mg/kg, fentanyl 5 μg/kg, and suxamethonium 1.5 mg/kg. Patients were manually ventilated when SpO 2 decreased to 90% in Subgroups A and 95% in Subgroups B, respectively, during apnea. 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) in 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 also 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 showed that younger children were more susceptible than older children to the risk of hypoxemia during apnea. There were significant differences in T 99, T 95, T 90, and T 95 − 90 between the three age groups. T 1 and T 2 were significantly longer in Group 3 than in Groups 1 and 2. There were significant differences in the lowest values of SpO 2 following 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%. Bradycardia was found in three children in Subgroups A. The apnea time to SpO 2 of 95% correlated well with age, weight, and height by linear regression analysis. Conclusions: The safe threshold of an apneic period setting to an SpO 2 of 95% was appropriate in children during anesthesia induction. Despite the same duration of preoxygenation, younger children were more susceptible than older ones to the risk of hypoxemia during apnea. The apnea time to Sp0 2 of 95% correlated with age, body weight, and height using linear regression analysis.