Liposomal bupivacaine incisional injection in single-level lumbar spine surgery.

BACKGROUND CONTEXT: Postsurgical pain control is important in spine surgery as it can lead to earlier mobilization, decreased length of stay, decreased side effects from narcotic medications, and improved patient satisfaction. Liposomal bupivacaine (LB) is an injectable formulation of bupivacaine, providing prolonged local anesthesia, up to 72 hours postinjection. Although, LB has been used with increasing frequency following other musculoskeletal procedures, specifically total joint replacements, its pre-emptive analgesic effect following lumbar microdiscectomy has hitherto not been reported. If administration of LB as a pre-emptive analgesic agent at the end of microdiscectomy resulted in reduced postoperative pain, then this could minimize adverse events related to narcotic pain medication use and improve acute clinical outcomes.

PURPOSE: The aim of the present study was to determine the comparative efficacy of infiltration of a standard dose and volume of LB in a comparative cohort analysis of single-level microdiscectomy procedures.

DESIGN: The present study made use of mixed prospective/retrospective observational cohort analysis.

PATIENT SAMPLE: Adult patients presenting with lumbar or sacral compressive disc disease treated with single-level microdiscectomy, at one institution utilizing a standard surgical technique.

OUTCOME MEASURES: Time spent on intravenous (IV) narcotics postoperatively (primary outcome), postoperative visual analog score (VAS), total morphine equivalent dose of narcotic pain medications, and 30-day emergency room visits for pain control were measured.

METHODS: Under an approved process improvement project, immediate outcome and process measures for a prospective cohort of 40 patients who received LB field blocks following single-level lumbar microdiscectomy were compared with a historical cohort of 40 patients who underwent the same surgical procedure but did not receive postsurgical infiltration of local anesthetic. All patients received a standard open surgical technique and postoperative convalescence protocol, which included overnight admission, oral narcotic pain medication as needed, scheduled IV ketorolac and IV narcotic pain medication for breakthrough.

RESULTS: Data from 80 subjects (67 males) operated on between January 2014 and 2015 were compared, including 40 cases, which occurred prior to using LB, and 40 cases after. There was no significant difference between mean age or body mass index (BMI) between groups. Patients who received LB infiltration spent significantly less time using IV narcotics in the postoperative period (LB patients 13.0±2.1 hours vs. non-LB patients 23.3±2.1 hours, p<.001). There was no significant difference noted between VAS at any point in the postoperative period, total injectable morphine equivalent doses, or 30-day emergency room visits for pain.

CONCLUSIONS: We found that patients who received LB field blocks required IV narcotic pain medication for a significantly decreased length of time (average delta=10.3 hours). Although this is a surrogate for earlier discharge, within the numbers studied, this did not translate into a significantdifference in VAS scores or total morphine equivalents. It is uncertain, if the independent effect of LB may have been masked by the multimodal postoperative pain control protocol in use. Further study is required to best understand the potential benefit of pre-emptive analgesia in elective spine surgery. Its impact would likely be more significant in more invasive procedures.