Correlation of oxygenation index and oxygen saturation index in patients undergoing emergency laparotomy under general anaesthesia: A prospective observational study

Oxygenation index (OI) was first investigated as a prognostic tool for acute hypoxemic respiratory failure in pediatric populations and has since been shown to be an independent risk factor for mortality in adults with acute respiratory distress syndrome. Patients and methods In this prospective cohort study, OI and oxygen saturation index (OSI) data of n = 201 adult patients undergoing emergency laparotomy were collected. Results Statistically significant correlation was found between OI and OSI both after induction of general anaesthesia [r2 = 0.61; p < 0.001] and at the end of surgery [r2 = 0.47; p < 0.001]. OSI after induction of general anaesthesia [AUC (SD) 0.74 (0.05); best cutoff 3.9, sensitivity 64% and specificity 45%] and at the end of surgery [AUC (SD) 0.77 (0.05); best cutoff 3.57, sensitivity 79% and specificity 62%] were reasonable predictors of postoperative mechanical ventilation. Exploratory analysis revealed age (p = 0.02), total leukocyte count (p = 0.002), serum lactate (p = 0.02) and driving pressure (p < 0.001) were independent predictors of hospital mortality Conclusion OI and OSI were correlated in adult patients undergoing emergency laparotomy under general anaesthesia. Both were able to predict the postoperative mechanical ventilation beyond 24 h and in-hospital mortality with reasonable accuracy.