Abstract
<title>Abstract</title> <p> Background Early recognition of major postoperative complications after bariatric surgery remains challenging. This study evaluated the diagnostic performance of early postoperative clinical and laboratory abnormalities. Methods <italic>A</italic> multicenter retrospective cohort study included 9,182 consecutive adults who underwent primary or revisional bariatric surgery at four tertiary centers between September 2016 and December 2020. Prespecified thresholds for routinely monitored postoperative clinical and laboratory parameters were evaluated. Results Among 9,182 patients, 87 (0.95%) developed major postoperative complications. Oxygen desaturation (SpO₂ ≤94%) was the strongest independent predictor (adjusted OR 28.88, 95% CI 14.08–59.24), followed by revisional surgery (adjusted OR 14.94, 95% CI 6.45–34.61), tachypnea, leukocytosis, anemia, severe postoperative pain, older age, and prolonged operative time. Oxygen desaturation demonstrated the highest diagnostic performance (specificity 99.3%; positive likelihood ratio [PLR], 106.7), while severe anemia (Hb ≤ 10 g/dL), fever (≥ 38°C), and severe postoperative pain also showed excellent rule-in performance (PLRs 10.3, 87.0, and 6.9, respectively). In contrast, tachycardia and tachypnea were sensitive but poorly specific screening indicators. Based on these findings, a practical bedside risk stratification framework integrating baseline procedural risk and early postoperative abnormalities was developed to support timely escalation of care. Internal bootstrap validation demonstrated excellent discrimination (optimism-corrected AUC 0.957) with minimal model optimism. Conclusions Major postoperative complications are characterized by physiologic and laboratory abnormalities. Oxygen desaturation, severe anemia, fever, and severe postoperative pain provide highly specific bedside indicators that should prompt early diagnostic evaluation. A structured postoperative assessment framework incorporating these variables may facilitate earlier recognition, timely intervention, and improved patient outcomes. Trial Registration ClinicalTrials.gov Identifier: NCT03556995 </p>