Perioperative Factors Associated with Severe Pain in Post-Anesthesia Care Unit after Thoracolumbar Spine Surgery: A Retrospective Case-Control Study.

STUDY DESIGN: A retrospective case-control study. PURPOSE: To evaluate the effect of nitrous oxide and anesthetic and operative factors associated with severe pain in the early postoperative period after thoracolumbar spine surgery. OVERVIEW OF LITERATURE: Thoracolumbar spine surgery is the most common procedure in spine surgery, and up to 50% of the patients suffer from moderate to severe pain. Nitrous oxide has analgesic, anxiolytic, and anesthetic effects; nevertheless, its benefits for early postoperative pain control and opioid consumption remain to be established. METHODS: The medical records of eligible participants who underwent thoracolumbar spine surgery between July 2016 and February 2017 were reviewed. Enrolment was performed consecutively until reaching 90 patients for the case (severe pain) group (patients with a pain score of >7 out of 10 at least once during the post-anesthesia care unit [PACU] admission), and 90 patients for the control (mild-to-moderate pain) group (patients with a pain score of <7 in every PACU assessment). The data collected comprised patient factors, anesthetic factors, surgical factors, PACU pain score, and PACU pain management. RESULTS: A total of 197 patients underwent thoracolumbar spine surgery with an incidence of early postoperative severe pain of 53.3%. The case-control study revealed no differences in the factors related to pain intensity. A subgroup analysis was performed for failed back surgery syndrome (FBSS), spinal stenosis, and spondylolisthesis. After multivariate analyses, only the age group of 19-65 years and the baseline Oswestry Disability Index (ODI) were found to be significant risk factors for early postoperative severe pain in the PACU (odds ratio [OR], 2.86; 95% confidence interval [CI], 1.32-6.25; OR, 1.03; 95% CI, 1.01-1.05, respectively). CONCLUSIONS: Nitrous oxide, anesthetic agents, and surgical techniques did not affect the early postoperative pain severity. Age under 66 years and the baseline ODI were the significant risk factors for pain intensity during the early postoperative period of the FBSS, spinal stenosis, and spondylolisthesis subgroups.