The effect of continuous interscalene brachial plexus block with 0.125% bupivacaine vs 0.2% ropivacaine on pain relief, diaphragmatic motility, and ventilatory function.

STUDY OBJECTIVE: Outpatient continuous interscalene brachial plexus blocks containing bupivacaine or ropivacaine are commonly used to control pain after shoulder surgery. Interscalene blocks cause hemidiaphragmatic paresis. Because ropivacaine preferentially blocks sensory fibers, it may cause less blockade of the phrenic nerve. The purpose of this study was to evaluate the effects of 2 common continuous interscalene brachial plexus infusions: 0.125% bupivacaine vs 0.2% ropivacaine. The study hypothesis is that respiratory function will be less attenuated using ropivacaine than bupivacaine without affecting pain relief.

DESIGN: Study design was a prospective randomized double-blind study, registered (NCT 02059070), with institutional review board approval and written informed consent.

SETTING: The setting was the preoperative and postoperative area in an orthopedic teaching hospital.

PATIENTS: Outpatients scheduled for shoulder arthroscopic surgery were included.

INTERVENTIONS: All patients underwent baseline measurements and interscalene catheter placement, then randomized to receive pumps containing either 0.2% ropivacaine or 0.125% bupivacaine.

MEASUREMENTS: Study measurements included preoperative and postoperative bedside spirometry and ultrasonographic evaluations of diaphragmatic excursion, postoperative pain scores, and postdischarge oral opioid (oxycodone) consumption.

MAIN RESULTS: There were no statistically significant differences between bupivacaine vs ropivacaine in outcomes of forced expiratory volume at 1 second change (-22% ± 18.3% vs -29% ± 14.9%), diaphragmatic excursion (-81.4% ± 37.95% vs -75.5% ± 35.1%), VAS pain scores at rest (4.9 ± 2.9 vs 3.5 ± 2.8), or oral opioid consumption (33.7 ± 24.3 mg vs 35.1 ± 33.9 mg).

CONCLUSIONS: There was no difference in respiratory dysfunction or opioid requirements between interscalene continuous peripheral nerve blocks with 0.125% bupivacaine or 0.2% ropivacaine. Further study is required to identify anesthetic infusates that will control pain while decreasing the attenuation of pulmonary function.