• Steven H Renes, Geert J van Geffen, Harald C Rettig, Mathieu J Gielen, and Gert J Scheffer.
• Department of Anesthesiology, Radboud University Nijmegen Medical Centre, Nijmegen, the Netherlands. s.renes@anes.umcn.nl
• Reg Anesth Pain Med. 2010 Nov 1;35(6):529-34.

Background And ObjectivesThis study was performed to determine the minimum effective volume of ropivacaine 0.75% required to produce effective shoulder analgesia for an ultrasound (US)-guided block at the C7 root level with assessment of pulmonary function.MethodsUsing the Dixon and Massey up-and-down method study design, 20 patients scheduled for elective open shoulder surgery under combined general anesthesia and continuous interscalene brachial plexus block were included. Initial volume of ropivacaine 0.75% was 6 mL; block success or failure determined a 1-mL decrease or increase for the subsequent patient, respectively. General anesthesia was standardized. A continuous infusion of ropivacaine 0.2% was started at a rate of 6 mL/hr at 2 hrs after completion of surgery. Ventilatory function was assessed using spirometry, and movement of the hemidiaphragm was assessed by US.ResultsThe minimum effective volume of local anesthetic in 50% and 95% of the patients was 2.9 mL (95% confidence interval, 2.4-3.5 mL) and 3.6 mL (95% confidence interval, 3.3-6.2 mL), respectively. Ventilatory function and hemidiaphragmatic movement was not reduced up to and including 2 hrs after completion of surgery, but 22 hrs after start of the continuous infusion of ropivacaine 0.2%, ventilatory function and hemidiaphragmatic movement were significantly reduced (P < 0.001).ConclusionsThe minimum effective volume of local anesthetic for shoulder analgesia for a US-guided block at the C7 root level in 50% and 95% of the patients was 2.9 and 3.6 mL, respectively. Pulmonary function was unchanged until 2 hrs after completion surgery, but reduced 22 hrs after start of a continuous infusion of ropivacaine 0.2%.

42 keywords...

hide…