Preoperative Inflammatory Ratios and Severe Intraoperative Hypoxemia During One-Lung Ventilation: A Prospective Observational Study.

(1) Background: One-lung ventilation (OLV) is frequently required during thoracic surgery, but hypoxemia remains a common intraoperative complication. Neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) have emerged as inexpensive inflammatory biomarkers, although their role in predicting hypoxemia during OLV remains unclear. This study evaluated the association between preoperative NLR, PLR, and severe intraoperative hypoxemia during OLV. (2) This interim analysis included 103 patients undergoing elective thoracic surgery with OLV in a prospective observational cohort. Severe hypoxemia was defined as PaO2/FiO2 < 100. Group comparisons were performed using Mann-Whitney U and chi-square/Fisher's exact tests. Hierarchical logistic regression and ROC analysis were used to evaluate predictors and model performance. (3) Results: Preoperative PLR significantly improved the predictive performance of the clinical model for severe intraoperative hypoxemia, while NLR was not associated with the outcome. BMI remained an independent predictor of hypoxemia. (4) Conclusions: PLR improved the predictive performance of the clinical model, although its inverse association with hypoxemia should be interpreted cautiously. NLR was not associated with hypoxemia during OLV.