Effect of Ketamine Added to Ropivacaine in Nerve Block for Postoperative Pain Management in Patients Undergoing Anterior Cruciate Ligament Reconstruction: A Randomized Trial.

ABSTRACT

PURPOSE: Nerve blocks are commonly used as a part of multimodal pain relief. It was previously shown that ketamine could enhance the analgesic effect of local anesthetics in nerve blocks. A literature review on adding ketamine to local anesthetics for ameliorating analgesia revealed inconsistencies in analgesic efficiency and safety. This prospective, randomized, double-blind trial was performed to evaluate the antinociceptive effect of mixing ketamine with local anesthetics in a combined femoral and sciatic nerve block (CFSNB) during anterior cruciate ligament (ACL) reconstruction. METHODS: Seventy-six patients undergoing preoperative ultrasound-guided CFSNB in ACL reconstruction were enrolled. Patients were randomly assigned to 3 groups Group RNK received perineural administration of 40-mg ketamine plus 0.375% ropivacaine in 40-mL volume; Group RIK received 40 mL of 0.375% ropivacaine, as well as IV ketamine 40 mg; and Group R received 40 mL of 0.375% ropivacaine. Pain scores were recorded. AUC was calculated based on the pain scores at different times. Duration of CFSNB, postoperative analgesic demand, time to first analgesic demand, and adverse events were also examined. FINDINGS: Perineural ketamine decreased pain scores 20 and 24 h' postoperatively, as well as lowered AUC values (all, P = 0.001). Group RNK had a prolonged time to first analgesic request (P = 0.014), inhibited rebound pain (P = 0.001), and increased satisfactory score at 48 h' postsurgery (P = 0.001). Perineural ketamine prolonged the duration of sensory block (P = 0.001) with no effect on early mobilization. There were no significant differences between Group R and Group RIK in terms of postoperative pain scores, AUC of different time intervals (P = 0.832 or more), and time to first rescue analgesics (P = 0.585). Compared with the 2 other groups, IV ketamine had a higher incidence of hallucination after operations. IMPLICATIONS Perineural ketamine added to the ropivacaine-enhanced analgesic efficacy of CFSNB with less rebound pain compared with the IV ketamine and control groups. IV ketamine had no effect in potentiating analgesia when a conventional multimodal approach was used in the study. Chinese Clinical Trial Registry ChiCTR1900023867.