Surgical site infection (SSI) after colorectal surgery is the leading cause of postoperative morbidity. Opioids induce immunosuppression through activation of μ-opioid receptors expressed on leucocytes, and through opioid withdrawal. A high dose of opioid administered as remifentanil during surgery may induce immunosuppression, leading to the development of SSI.

The purpose of this study was to investigate the influence of remifentanil on the development of SSI.

Adult patients who underwent elective colorectal surgery from January 2009 to December 2012 (N = 286) were prospectively investigated according to the guidelines of the US Centers for Disease Control and Prevention. After exclusion of 51 patients, propensity matching was performed in 235 patients. To reduce the influence of selection on SSIs, propensity score pairwise matching was performed for patients maintained with remifentanil and for patients maintained with fentanyl.

The number of patients who developed SSI was higher after remifentanil-based anaesthesia compared with fentanyl-based anaesthesia [11.6% (17/146) vs 3.4% (3/89), remifentanil vs fentanyl, P = 0.03] before propensity matching. Propensity matching yielded 61 pairs of patients anaesthetized with remifentanil or fentanyl, and corrected several biases in the preoperative patient characteristics. After propensity matching, the number of patients who developed SSI was still higher after remifentanil-based anaesthesia than after fentanyl-based anaesthesia [16.4% (10/61) vs 3.3% (2/61), remifentanil vs fentanyl, P = 0.029].

Remifentanil-based anaesthesia increased the incidence of SSI. A possible reason may be opioid-induced immunosuppression or opioid withdrawal-induced immunosuppression.