Background: Maintaining spontaneous ventilation in children, using total intravenous anesthesia (TIVA), is often desirable, particularly for airway endoscopy. The aim of this study was to evaluate the effect of age on the dose of remifentanil tolerated during spontaneous ventilation under anesthesia maintained with infusions of propofol and remifentanil and to provide guidelines for the administration of remifentanil and propofol to maintain spontaneous ventilation in children.
Methods: Forty-five children scheduled for strabismus surgery were divided by age into three groups (group I: 6 months-3 years, group II: 3 years-6 years, and group III: 6 years-9 years). The propofol infusion was titrated using State Entropy as a pharmacodynamic endpoint and remifentanil infused, using a modified up-and-down method, with respiratory rate depression as a pharmacodynamic endpoint. A respiratory rate of just greater than 10, stable for 10 min, determined the final remifentanil infusion rate. The group mean was estimated from the final remifentanil infusion rate tolerated (RD(50)).
Results: The RD(50) of groups I, II, and III were 0.192 (0.08), 0.095 (0.04), and 0.075 (0.03) microg x kg(-1) x min(-1) respectively. Pair-wise comparisons between the groups for the rate of remifentanil tolerated revealed a statistically significant increase in the RD(50) in children less than 3 years of age compared with older children in groups II and III (P < 0.001). The relationship between remifentanil dose and age, weight or height was not linear.
Conclusions: Younger children, especially those aged less than 3 years, tolerate a higher dose of remifentanil while still maintaining spontaneous respiration. TIVA with spontaneous ventilation is readily achieved in younger children and infants.