Epidural anaesthesia and survival after intermediate-to-high risk non-cardiac surgery: a population-based cohort study.

Background: Although epidural anaesthesia and analgesia have numerous benefits, their effects on postoperative survival are unclear. We therefore undertook a population-based cohort study to determine whether perioperative epidural anaesthesia or analgesia is associated with improved 30-day survival.
Methods: We used population-based linked administrative databases to do a retrospective cohort study of 259 037 patients, aged 40 years or older, who underwent selected elective intermediate-to-high risk non-cardiac surgical procedures between April 1, 1994, and March 31, 2004, in Ontario, Canada. Propensity-score methods were used to construct a matched-pairs cohort that reduced important baseline differences between patients who received epidural anaesthesia or analgesia as opposed to those that did not. We then determined the association of epidural anaesthesia with 30-day mortality within these matched-pairs.
Findings: Of the 259 037 patients, 56 556 (22%) received epidural anaesthesia. Within the matched-pairs cohort (n=88 188), epidural anaesthesia was associated with a small reduction in 30-day mortality (1.7%vs 2.0%; relative risk 0.89, 95% CI 0.81-0.98, p=0.02).
Interpretation: Epidural anaesthesia and analgesia were associated with a small improvement in 30-day survival, but this effect should be interpreted cautiously. The estimate had borderline significance, despite a large sample size. Its absolute magnitude was also small, corresponding to a number needed to treat of 477. Our study, therefore, does not provide compelling evidence that epidural anaesthesia improves postoperative survival. Nonetheless, our results support the safety of perioperative epidural anaesthesia when used for indications other than improving survival (eg, improving postoperative pain relief, preventing postoperative pulmonary complications).