Catheter Orifice Configuration Influences the Effectiveness of Continuous Peripheral Nerve Blockade

Background and Objectives: We investigated perineural catheter threading distance and orifice configuration during continuous inter-scalene analgesia. Methods: One hundred fifty-three patients receiving an anterolateral interscalene catheter (catheter needle and nerve/plexus in a similar alignment) for elective shoulder surgery were randomized to 1 of 3 groups: following out-of-plane ultrasound confirmation of the needle tip immediately lateral to the C5/6 roots, a nonstimulating catheter was blindly advanced 0.5 cm (end-hole; n = 50), 2.5 cm (multiorifice; n = 50) or 5 cm (multiorifice; n = 53) beyond the needle tip. Ropivacaine 0.75% + lidocaine 1% (50: 50) 20 mL was administered preoperatively via the catheter before surgery under general anesthesia. A ropivacaine 0.2% 2 mL/hr elastomeric infusion with mandatory 6 hourly (and on demand) 5-mL boluses was continued for more than 48 hrs with tramadol available as rescue. Patients were questioned in the recovery room, at 24 and 48 hrs for numerical rating pain score (0-10), ropivacaine bolus, and tramadol consumption. Results: Patients were more frequently pain-free in the recovery room in the multiorifice 2.5 and 5 cm groups compared with the end-hole 0.5 cm group (94%, 91% vs 66%; P < 0.001). During the first 24 hrs, the end-hole group demonstrated an earlier time to first pain (median, 10 vs17, 15 hrs; P < 0.001), higher average pain (median, 3 vs 1, 2, P = 0.004), and more ropivacaine bolus (median, 5 vs 3, 3; P < 0.001) and tramadol consumption (P = 0.01). Groups 2.5 and 5 cm did not significantly differ in any outcomes. Conclusions: These results suggest that multiorifice catheters provide superior intermittent bolus continuous peripheral nerve blockade compared with end-hole catheters. For anterolateral approach interscalene catheter placement, there is minimal benefit, either way, to 2.5- or 5-cm blind catheter advancement.