Effective concentration (EC50) of sevoflurane for intraocular pressure measurement in anaesthetised children with glaucoma: A dose-finding study

Abstract

Background and Aim: Sevoflurane, a preferred anaesthetic for children, exhibits a dose-dependent reduction in intraocular pressure (IOP). However, consensus is lacking regarding optimal end-tidal sevoflurane concentration for safe IOP measurement. This study aimed to identify the concentration at which IOP measurement could be attempted without inducing movements in paediatric patients after inhalational induction. Methods: Two paediatric groups (1–12 months and 12–36 months) with glaucoma undergoing examination under anaesthesia were recruited. After induction with 8% sevoflurane and 100% oxygen, the first child had an end-tidal sevoflurane concentration maintained at 2% for 4 min, followed by IOP measurement. Success was defined as ‘no movement’, and subsequent concentrations (adjusted in 0.2% steps) were determined using the Dixon and Massey method based on the previous patient’s responses. Results: The study included 75 children. The effective concentration of sevoflurane causing ‘no movement’ during IOP measurement in 50% of the study population for successful IOP measurement was 1.98% (95% confidence interval [CI] 1.63, 2.17, P = 0.017) for 1–12 months group and 0.55% (95% CI 0.39, 0.66, P = 0.002) for 12–36 months group. Probit regression analysis yielded effective concentration of sevoflurane causing ‘no movement’ during IOP measurement in 95% of the study population values of 2.47% (95% CI 2.24, 4.58, P = 0.017) for 1–12 months group and 0.94% (95% CI 0.78, 1.57, P = 0.002) for 12–36 months group. Conclusion: In paediatric patients, a higher end-tidal sevoflurane concentration of 2% is needed for IOP measurement in 1–12 months age group compared to 0.5% required in 12–36 months age group, achieving success in 50% of the study population.