Association Between Intraoperative Arterial Oxygen Tension and Postoperative Opioid Consumption: A Large-Scale Cohort Study Using Overlap Weighting Analysis.

Background and Objectives: The clinical impact of hyperoxia, particularly its analgesic effects and potential pulmonary risks, remains controversial. This study investigated whether higher intraoperative arterial oxygen tension (PaO2) reduces postoperative analgesic requirements and its association with postoperative pulmonary complications (PPCs). Materials and Methods: This retrospective cohort study included 1194 patients undergoing non-cardiac surgery. Patients were categorized into lower PaO2 (PaO2 ≤ 200 mmHg) and higher PaO2 (PaO2 > 200 mmHg) groups based on intraoperative arterial blood gas analysis. Overlap weighting was used to balance baseline characteristics and intraoperative variables. Primary outcomes included postoperative opioid consumption (measured in morphine milligram equivalents, MME) at 0-24 and 24-48 h. Secondary outcomes included pain intensity, frequency of rescue analgesics, the incidence of PPCs and in-hospital mortality. Results: After overlap weighting, the higher PaO2 group showed significantly lower strong opioid consumption during the 24-48 h period compared to the lower PaO2 group (0.22 ± 0.04 vs. 0.50 ± 0.11 MME; adjusted p = 0.014). The frequency of rescue analgesics was significantly reduced in the higher PaO2 group (1.04 ± 0.06 vs. 1.35 ± 0.11; adjusted p = 0.007). However, pain intensity and the total MME for 0-24 h did not differ. There was no significant difference in the incidence of total PPCs or total adverse events between the two groups. Conclusions: Higher intraoperative PaO2 was associated with a significant decrease in opioid requirements during the postoperative 24-48 h and frequency of rescue analgesics without increasing PPCs and adverse events. These findings support the need for prospective studies to determine whether higher intraoperative PaO2 may have a clinically meaningful role in perioperative analgesic strategies.