Abstract:
Systematic literature review of the regional anaesthetic techniques used for analgesia following shoulder surgery concluded continuous interscalene block as the most effective analgesic technique for shoulder surgery, while subacromial local anaesthetic infiltration performed only marginally better than placebo. The review also identified knowledge deficiencies in continuous interscalene block pharmacology, and unresolved technical issues around interscalene catheter placement. Thus, six interventional studies on 798 patients receiving ultrasound-guided continuous brachial plexus block were conducted. A dose-finding study determined the optimal primary local anaesthetic bolus to prevent recovery room pain and minimise motor block, which was subsequently validated with a randomised trial. The impact of mandatory local anaesthetic boluses relative to a background infusion, the anterolateral and posterior interscalene catheter placement approaches and the effect of catheter threading distance and catheter orifice configuration were studied. To prevent recovery room pain, the ropivacaine 0.5% ED(volume)95 (95% CI) estimate was 20.5 mL (17.3-25.8). The ropivacaine 20 mL ED(concentration)95 (95% CI) estimate was 0.34% (0.29-0.43). Compared to a traditional higher dose, satisfaction was modestly higher for this new/lower dose. Pooled data regression analysis showed that increasing ropivacaine concentration increased grip weakness but not block duration. Both local anaesthetic volume and concentration were found to influence block duration. Postoperative pain, night awakenings and tramadol consumption were similar in patients receiving mandatory boluses at a lower background infusion rate compared to patients receiving PRN only boluses at a higher infusion rate, However, more patients receiving the higher infusion required a temporary infusion cessation due to side effects (p=0.02). Compared with interscalene catheters placed via a posterior approach, anterolateral approach interscalene catheters resulted in less pain in the recovery room, reduced tramadol consumption during the first 24 postoperative hours, reduced catheter threading difficulty and reduced catheter placement time. Patients who received a multi-orifice anterolateral catheter advanced 2.5 and 5 cm beyond needle tip were more frequently pain free in the recovery room compared with patients receiving an end-hole catheter advanced 0.5 cm. During the first 24 hours, the end-hole catheters were associated with an earlier time to first pain, higher “average pain”, and more ropivacaine bolus and tramadol consumption. Groups 2.5 and 5 cm did not significantly differ in any outcomes. Catheter orifice configuration was subsequently shown to not significantly affect the quality of continuous interscalene block. This work conducted in this thesis has further added to our knowledge of, while also improving the effectiveness/side effect balance of ultrasound-guided continuous brachial plexus block for analgesia after shoulder surgery.