Association between SII and postoperative pulmonary infection in elderly patients undergoing laparoscopic abdominal surgery

Abstract

Objectives: This study aimed to identify the contributing factors, including systemic immune-inflammation index (SII), for pulmonary infections in elderly patients undergoing laparoscopic abdominal surgery with tracheal intubation under general anesthesia.

Methods: A total of 356 eligible elderly patients were monitored post-surgery for pneumonia. Pathogens were identified from sputum samples, and factors like age, smoking, chronic obstructive pulmonary disease (COPD), intubation, anesthesia duration, and SII were analyzed for their influence on infection risk.

Results: The pathogens were predominantly Gram-negative bacteria, with Klebsiella pneumoniae being the most common (26%). Significant risk factors for developing pneumonia included advanced age, smoking, COPD, prolonged intubation, and extended anesthesia. A higher preoperative SII was associated with an increased risk of pneumonia and correlated with infection severity and elevated levels of inflammatory markers. Multivariate analysis identified age over 70 (OR = 1.273, p = 0.021), age over 80 (OR = 2.085, p < 0.001), COPD (OR = 1.528, p = 0.009), prolonged intubation >2 h (OR = 2.187, p < 0.001), general anesthesia >4 h (OR = 1.846, p = 0.006), operative time > 2 h (OR = 1.415, p = 0.016), and preoperative SII >489.3 (OR = 1.403, p = 0.012) as independent risk factors for postoperative pulmonary infection.

Conclusion: Our study highlighted critical risk factors for postoperative pulmonary infections in elderly patients undergoing laparoscopic abdominal surgery. Preoperative SII could be a novel predictor, offering potential for improved pre-surgical risk assessment.

Keywords: elderly patients; laparoscopic abdominal surgery; postoperative pulmonary infections; risk factors; systemic immune-inflammation index (SII).

Figure 1

Patient enrollment and outcomes flowchart. The flowchart depicting the progression of the study. Out of 420 assessed elderly patients, 356 were eligible and underwent laparoscopic abdominal surgery. Post-surgery, 112 patients developed pneumonia, while 244 did not. These cases were then advanced to the analysis phase.

Figure 2

Preoperative systemic immune-inflammation index as a predictor of postoperative pulmonary infection in elderly laparoscopic surgery patients. (A) Comparison of preoperative systemic immune-inflammation index (SII) between elderly patients with (n = 112) and without (n = 244) postoperative pulmonary infection who received laparoscopic abdominal surgery under tracheal intubation and general anesthesia. Data points represent individual patients with overlaying mean ± standard deviation (SD), and statistical significance assessed using an unpaired t-test with Welch’s correction (p < 0.001). (B) Receiver operating characteristic (ROC) curve evaluating the prognostic performance of preoperative SII in predicting postoperative pulmonary infection among elderly patients undergoing laparoscopic abdominal surgery. The area under the curve (AUC), sensitivity, and specificity are indicated, with statistical significance noted (p < 0.001).

Figure 3

Correlation of clinical pulmonary infection score (CPIS) with preoperative SII. Spearman correlation analysis of clinical pulmonary infection score (CPIS) at diagnosis of pulmonary infection with preoperative systemic immune-inflammation index (SII) in elderly patients with postoperative pulmonary infection who received laparoscopic abdominal surgery under tracheal intubation and general anesthesia (n = 112). p < 0.001.

Figure 4

Association between preoperative systemic immune-inflammation index (SII) and severity of infection in patients. Spearman correlation analysis of preoperative systemic immune-inflammation index (SII) with the concentrations of PCT in plasma (A), serum hs-CRP (B) at diagnosis of pulmonary infection in elderly patients with postoperative pulmonary infection who received laparoscopic abdominal surgery under tracheal intubation and general anesthesia (n = 112). p < 0.001.