Incidence and effects of postoperative migration of interscalene catheter tips placed using ultrasound-guided anterior and posterior approaches.

BACKGROUND: Continuous interscalene brachial plexus block (CISB) provides analgesia after shoulder surgery. However, even a catheter securely fixed at the insertion site may be susceptible to migration, precluding the block from working consistently. We examined to see if catheter tip migration would occur with no catheter-at-skin change after anterior and posterior approaches to CISB in patients undergoing shoulder surgery, and compared the incidence rate and pain scores between approaches and between catheters with and without tip migration, respectively. METHODS: Patients were randomly assigned to receive CISB using either anterior or posterior approach. Catheter tip was observed using a cross-sectional view. The rates of catheter tip migration with no catheter-at-skin change at 24 h after the two approaches were calculated and compared, and pain scores were compared between catheters with and without tip migration after each approach. RESULTS: Fifty-four patients were analyzed. Catheter tip migration occurred at 24 h at a similar rate after both approaches (anterior approach 40.7% versus posterior approach 33.3%, p = 0.78). Worst pain score was significantly higher for 24 h in patients whose catheter tip had migrated as compared with those whose catheter had not migrated after anterior (median [IQR] 53 [42-73] versus 18 [0-50], p = 0.003) and posterior approaches (median [IQR] 63 [57-81] versus 29 [3-47], p < 0.0001). CONCLUSION: In patients undergoing shoulder surgery, an interscalene catheter tip can migrate after both anterior and posterior approaches at a similar rate, even if the catheter insertion length is not changed. The tip migration does decrease the analgesic effect of CISB.