Early systemic inflammatory indices and postoperative SIRS after percutaneous nephrolithotomy under spinal versus general anaesthesia: a prospective cohort study

Abstract Objective Percutaneous nephrolithotomy (PCNL) may induce an early systemic inflammatory response. This study compared perioperative changes in systemic inflammatory indices between patients undergoing elective PCNL under spinal or general anaesthesia and explored the relationship of these indices with postoperative systemic inflammatory response syndrome (SIRS). Materials and methods This single-centre, prospective, non-randomised observational cohort study included consecutive adult patients undergoing elective PCNL between November 2025 and June 2026. Anaesthetic technique was determined as part of routine clinical care, and patients were classified according to the technique received. The primary outcome was the between-group comparison of perioperative changes in the neutrophil-to-lymphocyte ratio (NLR), systemic immune-inflammation index (SII), systemic inflammation response index (SIRI), and aggregate index of systemic inflammation (AISI), measured preoperatively and 6 h postoperatively. Secondary clinical outcomes were postoperative SIRS, fever, and length of hospital stay. Receiver operating characteristic analysis, decision curve analysis, and a parsimonious two-variable logistic regression analysis involving SIRS were performed as exploratory secondary analyses. Results A total of 150 patients were included in the final analysis, with 75 patients in each anaesthesia group. Preoperative inflammatory indices were similar between the groups, whereas postoperative NLR, SII, SIRI, and AISI values and their corresponding Δ values were significantly higher in the general anaesthesia group (all p < 0.001). Postoperative SIRS occurred in 5 patients (6.7%) in the spinal anaesthesia group and 16 patients (21.3%) in the general anaesthesia group ( p = 0.017), while postoperative fever occurred in 10.7% and 24.0%, respectively ( p = 0.031). Length of hospital stay did not differ significantly between groups. Among the evaluated inflammatory indices, ΔAISI showed the highest discriminatory performance for postoperative SIRS (AUC = 0.962, 95% CI: 0.923–0.991). In the exploratory parsimonious multivariable model, general anaesthesia (adjusted OR = 12.02, 95% CI: 1.06–136.68, p = 0.045) and ΔAISI (adjusted OR = 1.51 per 100-unit increase, 95% CI: 1.26–1.81, p < 0.001) were associated with postoperative SIRS after mutual adjustment. The wide confidence interval for general anaesthesia indicates substantial imprecision in the magnitude of this association. Conclusion General anaesthesia was associated with a more pronounced early postoperative inflammatory response and higher observed rates of SIRS and fever than spinal anaesthesia in this prospective observational cohort. ΔAISI showed the highest discriminatory performance for postoperative SIRS among the evaluated inflammatory indices; however, the SIRS-related analyses were exploratory and based on only 21 events. These findings require confirmation in larger independent cohorts before ΔAISI or its internally derived threshold can be considered for clinical risk stratification.