Minimum intraoperative perfusion index is associated with end-of-surgery hyperlactatemia under general anesthesia

The perfusion index (PI) is a continuously available pulse oximetry-derived marker of peripheral perfusion; however, its relationship with perioperative metabolic stress remains unclear. Although previous studies have examined intraoperative PI-related metrics and postoperative outcomes, whether the minimum intraoperative PI (PI min) is associated with end-of-surgery hyperlactatemia has not been well characterized. This study aimed to examine the association between PI min and end-of-surgery hyperlactatemia in patients undergoing surgery under general anesthesia. This single-center retrospective observational study reviewed 1,948 consecutive surgical cases performed under general anesthesia. Of these, 186 patients with intraoperative radial arterial catheterization and arterial blood gas analysis performed between the start of wound closure and operating room exit were included in the analysis. PI min was defined as the lowest PI recorded during surgery, excluding cardiopulmonary bypass periods. The primary outcome was end-of-surgery hyperlactatemia, defined as lactate > 2.0 mmol/L. Hyperlactatemia occurred in 40 patients (21.5%). Lower PI min was associated with hyperlactatemia ( p = 0.019), and this association remained significant after adjustment for age, sex, and surgical category (adjusted odds ratio per 0.1-unit increase, 0.73; 95% confidence interval, 0.57–0.95; p = 0.017). Receiver operating characteristic analysis showed modest discrimination (area under the curve, 0.657), with an exploratory ROC-derived cutoff of PI min < 0.08. PI min was moderately correlated with the time-weighted mean PI. Lower PI min was associated with end-of-surgery hyperlactatemia in patients undergoing general anesthesia with intraoperative arterial catheterization. To our knowledge, this study is among the first to specifically link the intraoperative PI nadir with end-of-surgery hyperlactatemia. PI min may serve as a simple intraoperative marker associated with metabolic evidence of hypoperfusion-related stress, although its discriminative performance was modest and prospective validation is required.