The 90% minimum effective volume and concentration of ropivacaine for ultrasound-guided median nerve block in children aged 1-3 years: A biased-coin design up-and-down sequential allocation trial

Background: Median nerve block can provide excellent analgesia during open surgery for trigger thumb in children. However, no data on the 90% minimum effective volume (MEV₉₀) and concentration (MEC₉₀) of ropivacaine for ultrasound-guided median nerve block in pediatric patients have been reported.

Design: A prospective two-phase study with an up-and-down sequential allocation trial using a biased coin design.

Patients: Children aged 1-3 years are experiencing open surgery for trigger thumb.

Intervention: This study has 2 parts, one for MEV₉₀ and subsequently studied MEC₉₀ from the former part of the study. The MEV₉₀ and MEC₉₀ of ropivacaine for each subsequent patient were determined by the response of the previous patient, with the biased coin design up-and-down sequential allocation trial. The interval of -volume or concentration was -0.1 ml or 0.01%, respectively.

Measurements: The MEV₉₀ and MEC₉₀ of ropivacaine for ultrasound-guided median nerve block in pediatric patients, were then used to estimate the 99% minimum effective volume (MEV₉₉) and concentration (MEC₉₉). The patient's general condition, postoperative pain, and adverse events.

Main results: A total of one hundred and eighteen children were enrolled for the study, and 56 and 62 patients were enrolled for the MEV₉₀ and MEC₉₀ studies, respectively. The MEV₉₀ of 0.2% ropivacaine was 1.44 ml (95% CI 1.043 ml, 1.466 ml), and the MEC₉₀ of 1.5 ml ropivacaine was 0.195% (95% CI 0.159%, 0.197%). There were no adverse events that occurred.

Conclusion: For ultrasound-guided median nerve block in children aged 1-3 years old with trigger finger undergoing open surgery, the MEV₉₀ of 0.2% ropivacaine is 1.44 ml (95% CI 1.043 ml, 1.466 ml), and the MEC₉₀ of 1.5 ml of ropivacaine is 0.195% (95% CI 0.159%, 0.197%).