Postoperative Nausea and Vomiting After Open Lumbar Discectomy: A Secondary Analysis of a Randomized Trial Using Adequacy of Anesthesia Monitoring

<b>Background/Objectives</b>: Postoperative nausea and vomiting (PONV) remains a frequent and clinically relevant complication following open lumbar discectomy (OLD) under general anesthesia. The present study represents a secondary, post hoc analysis of a randomized controlled trial originally designed to investigate the effects of infiltration anesthesia (IA) on postoperative pain perception and opioid consumption. The objective of this analysis was to explore the incidence of PONV in patients undergoing OLD under adequacy of anesthesia (AoA)-guided general anesthesia, with or without IA. <b>Methods</b>: This secondary analysis included 94 patients undergoing OLD under AoA-guided general anesthesia with fentanyl titration based on the surgical pleth index (SPI). Patients were randomized to receive IA with 0.2% ropivacaine (RF) or bupivacaine (BF) plus 50 µg fentanyl, or no IA (control). PONV was assessed as early (in the post-anesthesia care unit), late (in the neurosurgical ward), and overall (within 48 h postoperatively). Opioid consumption and Apfel risk scores were also analyzed. All analyses related to PONV were exploratory. <b>Results</b>: PONV occurred in 12.8% of patients, with no significant differences between study groups. Postoperative morphine consumption was significantly lower in the RF group than in the control group (2.7 ± 5.3 mg vs. 7.1 ± 5.9 mg; <i>p</i> < 0.05). Higher pre-induction SPI values were observed in patients who experienced early PONV (73.1 ± 9.7 vs. 59.5 ± 17.2; <i>p</i> < 0.05); however, this exploratory finding requires confirmation in larger studies. <b>Conclusions</b>: In this secondary, post hoc analysis, no significant differences in PONV incidence were observed between anesthetic groups in patients undergoing OLD under AoA-guided general anesthesia. The observed association between pre-induction SPI values and early PONV should be interpreted cautiously and requires confirmation in adequately powered prospective studies.