To evaluate the influence of age factors on dose-effect relationship of oxycodone inhibiting responses to tracheal intubation during induction of general anesthesia in pediatric patients.

American Society of Anesthesiologists Physical Status classification Ⅰ or Ⅱ pediatric patients of both sexes, aged 6 months-6 yr, with body mass index of 12-22 kg/m^2, scheduled for elective surgery under general anesthesia with tracheal intubation, were divided into 3 groups: infant group (group I, 6-12 months), young children group (group Y, >1-3 yr) and preschooler group (group P, >3-6 yr). Oxycodone was slowly injected intravenously, 2 min later etomidate 0.3 mg/kg and cisatracurium 0.15 mg/kg were intravenously injected, and 3 min later endotracheal intubation was carried out with a visual laryngoscope in all the children. Mean arterial pressure(MAP) and heart rate (HR) immediately before intubation and peak MAP and HR within 3 min after intubation were recorded. The modified Dixon′s sequential method was used. The initial dose of oxycodone was 0.3 mg/kg in each group. If the response to tracheal intubation was positive, the dose of oxycodone was increased by 0.02 mg/kg in the next child; if the response to tracheal intubation was negative, the dose of oxycodone was decreased by 0.02 mg/kg in the next child. Positive response to tracheal intubation was defined as increase in MAP and/or HR and increase in the peak value exceeding 20% of the pre-intubation level within 3 min after tracheal intubation. The aforementioned process was repeated until 7 negative and positive reactions crossed, and then the test was stopped. The median effective dose (ED₅₀) and 95% confidence interval of oxycodone were calculated by Probit method.

The ED₅₀ (95% confidence interval) of oxycodone inhibiting responses to the tracheal intubation were 0.280 (0.247-0.301) mg/kg, 0.321 (0.304-0.342) mg/kg and 0.354 (0.342-0.368) mg/kg in I, Y and P groups, respectively. The ED₅₀ of oxycodone inhibiting responses to the tracheal intubation was gradually increased during induction of general anesthesia with increasing age (P<0.05).

For children aged 6 months to 6 yr, the potency of oxycodone in inhibiting responses to the tracheal intubation during general anesthesia induction gradually decreases with increasing age.

Age factors; Child; Oxycodone; Dose-response relationship, drug; Intubation, Intratracheal