Particulate-steroid betamethasone added to ropivacaine in interscalene brachial plexus block for arthroscopic rotator cuff repair improves postoperative analgesia

BACKGROUND: Dexamethasone added to local anesthetic for brachial plexus block improves postoperative pain after arthroscopic rotator cuff repair, as compared with the use of local anesthetic alone. Dexamethasone is present in non-particulate form in local anesthetic solution, while betamethasone is partially present in particulate form. The particulate betamethasone gradually decays and is expected to cause its longer-lasting effect. This study investigated the postoperative analgesic effect of betamethasone added to ropivacaine for brachial plexus block in patients who underwent arthroscopic rotator cuff repair. METHODS: This was a prospective, randomized, triple-blind study of 44 patients undergoing arthroscopic rotator cuff repair surgery. Ultrasound-guided interscalene brachial plexus block, involving 20 mL of 0.375 % ropivacaine (group R) or 19 mL of 0.375 % ropivacaine with 4 mg (1 mL) of betamethasone (group BR), was administered and surgery was performed under general anesthesia. After surgery, the pain score was recorded at 12 h after surgery, and on the first, second, and seventh postoperative day. Analgesia duration, offset time of motor block, frequency of rescue analgesic administration, postoperative nausea/vomiting, and sleep disturbance during the night after surgery were recorded. The numerical values were expressed as median [interquartile range]. P values < 0.05 were considered statistically significant. RESULTS: The duration of analgesia was significantly prolonged in group BR (group BR: 19.1 h [16.6, 20.9 h], group R: 13.3 h [11.6, 16.5 h], p < 0.001). The pain scores at 12 h after surgery and on the first and seventh day after surgery were significantly lower in group BR than in group R. The duration of motor block was significantly prolonged in group BR. The frequency of rescue analgesic administration and the sleep disturbance rate were significantly lower in group BR. There was no difference in postoperative nausea/vomiting between the two groups. CONCLUSIONS: Betamethasone added to local anesthetic in interscalene brachial plexus block improved postoperative pain after arthroscopic rotator cuff repair, and betamethasone prolonged the duration of analgesia by almost 6 h. TRIAL REGISTRATION: University Hospital Medical Information Network Center Clinical Trials Registration System (UMIN000012899). ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12871-016-0251-9) contains supplementary material, which is available to authorized users.