Association of Preoperative Plateletcrit and Other Inflammatory Indices with Postoperative Pain Severity and Opioid Consumption in Morbidly Obese Patients Receiving Transversus Abdominis Plane Block: A Retrospective Observational Study

Background: Bariatric surgery induces a systemic inflammatory response to surgical stress that may influence postoperative pain and analgesic requirements, and CBC-derived inflammatory indices can reflect preoperative and postoperative immunometabolic dynamics related to this response. This retrospective observational search evaluated whether inflammatory indices derived from routine complete blood counts are associated with postoperative pain and opioid consumption after ultrasound-guided transversus abdominis plane (TAP) block in patients with morbid obesity. Methods: In this retrospective observational search, 120 patients undergoing bariatric surgery were divided into two groups: TAP block (Group T, n = 59) and local infiltration of the trocar insertion site (Group K, n = 61). Preoperative and postoperative 24-hour hematological indices, VAS pain scores (0, 2, 6, 12, 24 h), and cumulative 24-hour opioid consumption were analyzed. Results: Group T had significantly lower 24-hour opioid consumption and VAS scores at all time points. Regarding changes between groups, the increase in neutrophil counts was greater in Group T than in Group K, whereas the change in SIRI values was smaller in Group T compared to Group K. ROC analysis showed no clinical benefit for NLR, PLR, SII, or SIRI. Only PCT (Plateletcrit) showed weak inverse discriminative ability. Conclusion: Compared with trocar site local anesthetic infiltration using an equivalent bupivacaine dose, TAP block was associated with lower postoperative pain and opioid consumption. The smaller postoperative rise in SIRI observed in the TAP block group is an exploratory, hypothesis-generating finding that did not survive correction for multiple comparisons and should not be interpreted as evidence of a causal anti-inflammatory effect. Overall, CBC-derived inflammatory indices did not perform as reliable predictive biomarkers for postoperative analgesic outcomes in this bariatric surgery population.