To determine the median effective dose (ED₅₀) and the 95% effective dose (ED₉₅) of 0.2% ropivacaine for ultrasound-guided lower forearm median nerve block in paediatric patients.

Eligible children were American Society of Anesthesiologists (ASA) status I–II scheduled to have elective open surgery for trigger thumb repair. Patients were stratified into two age groups: 1- to 3-year-olds and 3- to 6-year-olds. The ED₅₀ was determined by Dixon’s up-and-down method. The first patient received an ultrasound-guided median nerve block by injection of 2 mL of 0.2% ropivacaine. Each subsequent patient’s dose was determined by the response of the previous patient, the doses being adjusted in intervals of 0.2 mL. In addition, the 95% effective dose (ED₉₅) was obtained using a probit regression approach. The patients’ general condition, postoperative pain scores, and adverse events were recorded.

A total of 52 children who were scheduled to undergo open surgery for trigger thumb were included in this study: 28 in the 1- to 3-year-olds group and 24 in the 3- to 6-year-olds group. The ED₅₀ (95% confidence interval) values were 0.9 (0.44–1.36) mL in 1- to 3-year-olds and 1.4 (1.14–1.66) mL in 3- to 6-year-olds. The ED₉₅ (95% confidence interval) values were 1.5 (0.98–1.58) mL in 1- to 3-year-olds and 1.7 (1.54–1.78) mL in 3- to 6-year-olds. No adverse events occurred.

A single dose of ropivacaine was an effective agent for young children requiring ultrasound-guided lower forearm median nerve block in open surgery for trigger thumb. The ED₅₀ (95% confidence interval) values were 0.9 (0.44–1.36) mL in 1- to 3-year-olds and 1.4 (1.14–1.66) mL in 3- to 6-year-olds. The ED₉₅ (95% confidence interval) values were 1.5 (0.98–1.58) mL in 1- to 3-year-olds and 1.7 (1.54–1.78) mL in 3- to 6-year-olds.