DOES ADDITION OF LONGER-ACTING LOCAL ANAESTHETIC IMPROVE POSTOPERATIVE PAIN AFTER CARPAL TUNNEL RELEASE? A RANDOMIZED CONTROLLED TRIAL

Carpal tunnel release (CTR) is a simple and effective treatment for carpal tunnel syndrome in patients who have failed conservative management. In Canada, this surgery is often performed in the ambulatory clinic under local anesthesia, with lidocaine (a short-acting agent) as the drug of choice. Post-operative pain is a concern for many patients, and a previous study at our institution found that maximal pain was experienced 8 hours after surgery. Although use of a longer-acting anesthetic, such as bupivacaine, should theoretically prolong the post-operative pain blockade, few studies have investigated its use for CTR. Therefore, the aim of our study was to compare the post-operative pain experience after CTR with the use of either our standard lidocaine solution (L) or a longer-acting mixture consisting of lidocaine and bupivacaine in equal amounts (LB). Patients undergoing CTR were randomized into L or LB groups. Post-operative pain severity was recorded at several timepoints within the first 72 hours, using the Visual Analog Scale (VAS). The timing and quantity of post-operative analgesic use (Tylenol and/or Advil) were also documented. Both patients and assessor were blinded to allocation. A total of 145 patients were recruited. After exclusions, 139 remained: 67 (48.2%) in the L group and 72 (51.8%) in the LB group. Mean age of patients in the L group (56.9 years) was significantly lower than that of the LB group (63.0 years) (p=0.02). Baseline carpal tunnel severity scores were similar between groups. Compared to the L group, post-operative VAS scores were significantly lower in the LB group at 6 hours (2.3 vs 3.2, p=0.02) and 8 hours (2.9 vs 3.9, p=0.02). Additionally, patients in the LB group reported longer time to first analgesic use than those in the L group (5.2 hours vs. 3.7 hours, p=0.02). Our results suggest that patients anesthetized with a mixture of lidocaine and bupivacaine for CTR experienced less postoperative pain at 6 and 8 hours, compared with those who received lidocaine alone. In our experience, this mixture is a feasible alternative to lidocaine for CTR performed under local anesthesia.