Minimum effective volume of local anesthetic for shoulder analgesia by ultrasound-guided block at root C7 with assessment of pulmonary function

Reg Anesth Pain Med. Nov-Dec 2010;35(6):529-34. doi: 10.1097/AAP.0b013e3181fa1190.

Abstract

Background and objectives: This 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.

Methods: Using 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.

Results: The 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).

Conclusions: The 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%.

Publication types

  • Clinical Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Amides / administration & dosage*
  • Analgesia / methods*
  • Anesthetics, Local / administration & dosage*
  • Cervical Vertebrae / diagnostic imaging
  • Diaphragm / diagnostic imaging
  • Diaphragm / drug effects*
  • Double-Blind Method
  • Female
  • Humans
  • Infusions, Parenteral
  • Male
  • Middle Aged
  • Nerve Block*
  • Netherlands
  • Pain Measurement
  • Pain, Postoperative / etiology
  • Pain, Postoperative / prevention & control*
  • Prospective Studies
  • Pulmonary Ventilation / drug effects*
  • Ropivacaine
  • Shoulder / innervation*
  • Shoulder / surgery
  • Shoulder Pain / etiology
  • Shoulder Pain / prevention & control*
  • Spirometry
  • Time Factors
  • Treatment Outcome
  • Ultrasonography, Interventional*

Substances

  • Amides
  • Anesthetics, Local
  • Ropivacaine