Abstract
Epidural analgesia studies and a recent continuous peripheral nerve block study suggest multi-hole perineural catheters perform better than end-hole catheters. Confounding catheter positioning issues limit interpretation of the latter study. One hundred and fifty-six patients receiving an anterolateral interscalene catheter for elective shoulder surgery were randomised to three groups: following out-of-plane ultrasound confirmation of the needle tip immediately lateral to the C5/6 roots, an end-hole (n=52), triple-hole (n=53) or six-hole (n=51) non-stimulating catheter was positioned 3 cm beyond the needle tip. Ropivacaine 0.375% 15 ml was administered preoperatively via the catheter before surgery under general anaesthesia. A ropivacaine 0.2% 2 ml/hour infusion with mandatory six-hourly, and on-demand hourly, 5 ml boluses was continued for >48 hours with tramadol available as rescue. Patients were questioned in the recovery room and at 24 hours for numerical rating pain score (0 to 10), ropivacaine bolus and tramadol consumption. The frequency of recovery room pain was similar between groups (P=0.75) and demonstrated strong evidence for equivalence at the 5% significance level. Neither time to first pain, “average” or “worst” pain during the first 24 hours, ropivacaine bolus or tramadol consumption significantly differed between groups. Catheter threading difficulty was more common for the square-tipped end-hole catheters (end-hole=19% versus triple-hole=6%, six-hole = 0%, P <0.001). This study found no evidence to support catheter orifice configuration significantly affecting the quality of continuous peripheral nerve blockade. These findings are in contrast to epidural catheter studies, and suggest that anatomical factors have a significant bearing on whether multi-orifice catheters confer advantage over the single-orifice design.