Analgesic effectiveness of a continuous versus single-injection interscalene block for minor arthroscopic shoulder surgery.

BACKGROUND AND OBJECTIVES: The utility of continuous perineural infusions for lesser painful shoulder procedures is not well established. We hypothesized that the addition of a continuous interscalene ropivacaine infusion to a single-injection interscalene block would improve analgesia after minor arthroscopic shoulder surgery.

METHODS: An ultrasound-guided interscalene catheter targeting the C5-C6 roots/superior trunk was placed preoperatively in patients undergoing arthroscopic subacromial decompression, excision lateral clavicle, or stabilization. Ropivacaine 0.5% 30 mL was administered via this catheter before surgery was conducted under general anesthesia. All patients received dexamethasone and ondansetron antiemetic prophylaxis. At surgery conclusion, patients were randomly assigned to catheter removal in the postanesthesia care unit ("SS," n = 30) or to an elastomeric infusion of ropivacaine 0.2% 2 mL/hr with patient-controlled 5-mL boluses every hour ("Continuous," n = 31). Multimodal analgesia (acetaminophen, diclofenac, and rescue tramadol) was administered in both groups. Patients were questioned on postoperative days 1 and 2 for numerical rating pain score (0-10), supplemental tramadol consumption, and adverse effects of treatment.

RESULTS: Median (quartiles) worst numerical rating pain score was lower in the Continuous group on day 1 on movement (SS = 4 [3-6], Continuous = 2 [0-4], P = 0.008) and at rest (SS = 2 [2-5], Continuous = 1 [0-3], P = 0.007) but was similar between groups on day 2. Median (quartiles) tramadol tablet consumption was lower in the Continuous group on both day 1 (SS = 1 [0-2], Continuous = 0 [0-0], P < 0.001) and day 2 (SS = 1 [0-2], Continuous = 0 [0-1], P = 0.017). Adverse effects of treatment were similar between groups except for numerically rated arm numbness, which was higher for the Continuous group. One patient in the SS group required 2 nights of hospitalization for intravenous opioid.

CONCLUSIONS: After minor arthroscopic shoulder surgery, the addition of a continuous interscalene ropivacaine infusion to a single-shot interscalene block reduces pain, especially with movement, during the first 24 hrs.