Association Between Surgical Timing and Perioperative Outcomes in Lumbar Spine Surgery: A Retrospective Cohort Study

Background/Objectives: The impact of surgical timing on perioperative outcomes remains a subject of ongoing debate. Although after-hours surgery has been associated with adverse outcomes in various surgical populations, its role in lumbar spine surgery remains unclear. This study aimed to evaluate factors associated with postoperative intensive care unit (ICU) admission in patients undergoing lumbar spine surgery. Methods: In this retrospective observational study, 460 patients who underwent lumbar spine surgery were analyzed. Patients were categorized according to the timing of surgery as in-hours or after-hours. Demographic, clinical, intraoperative, and laboratory parameters were compared between the two groups. Multivariable logistic regression analysis was performed to evaluate factors associated with postoperative ICU admission. Results: Of the 460 patients, 380 (82.6%) underwent surgery during in-hours and 80 (17.4%) after-hours. The baseline characteristics, including age, sex, and comorbidities, were comparable between the two groups. ICU admission was significantly more frequent in the after-hours group (45.0% vs. 19.5%, p < 0.001), whereas the length of hospital stay and intraoperative variables were similar between the two groups. Preoperative laboratory analysis revealed higher inflammatory markers (NLR and SII) and lower albumin levels in the after-hours group (all p < 0.05), whereas postoperative values were comparable. In the multivariable analysis, after-hours surgery remained independently associated with ICU admission (adjusted OR 4.82, 95% CI 2.15-10.78, p < 0.001). Lower preoperative albumin and higher preoperative NLR demonstrated borderline significance. Conclusions: After-hours lumbar spine surgery was associated with a significantly increased rate of ICU admission, even after adjustment for patient characteristics, surgical urgency, and clinical indications. These findings suggest that surgical timing may contribute to increased perioperative resource utilization and highlight the potential role of system-level and organizational factors in influencing perioperative outcomes.