Study analyses anesthetic effects on surgical site infections

A study appearing in the August 2010 issue of Anesthesiology found that patients receiving a total hip or knee replacement in Taiwan had a higher incidence of surgical site infections (SSIs) when general anesthesia was administered for the operation than when the same procedures were performed under epidural/spinal (regional) anesthesia.

"Many anesthetics used in general anesthesia have been shown to compromise immunity responses," said Chuen-Chau Chang, M.D., M.P.H., Ph.D., lead author on the study. "To the best of our knowledge, this is the first study to verify the anesthetic effects on surgical site infections using a large-scale, real-life data set."

About the Study
The study used Taiwan's Longitudinal Health Insurance Database. A total of 3,081 patients who underwent primary total hip or knee replacement from 2002 to 2006 were included, and the study looked for SSIs occurring within 30 days of surgery.

The study found:
•Of the 3,081 patients sampled, 56 patients (1.8 percent) had SSIs within 30 days.
•Of those 56 patients with infections, 33 (2.8 percent of all under general anesthesia) had general anesthesia and 23 (1.2 percent of all under epidural or spinal anesthesia) had epidural or spinal anesthesia>•For patients who underwent general anesthesia during surgery, the odds of getting an SSI were 2.2 times higher than for those who had the same procedure under epidural/spinal anesthesia, after adjusting for the patients' age, sex, the year of surgery, comorbidities, surgeon's age, and hospital teaching status.

"The study's findings support the evolving concept of long-term consequences of anesthesia," said Dr. Chang. "This research demonstrates that anesthetic choices may impact a patient beyond the operating room and hospital stay which could increase in-hospital and post-discharge financial burdens."

Analysis of the Study
An editorial appearing in the August issue regarding the study applauds the findings as "compelling epidemiologic evidence that the use of neuraxial (epidural/spinal) anesthesia also reduces risk [of SSIs]," according to Daniel I. Sessler, M.D., Department of Outcomes Research, Anesthesiology Institute, The Cleveland Clinic.

In his editorial, Dr. Sessler outlines existing strategies for preventing SSIs, including: administering antiobiotics, providing supplemental oxygen, and minimizing red cell transfusions. Dr. Sessler highlighted the following potential reasons why spinal/epidural anesthesia demonstrated lower infection rates:
1.Spinal/epidural anesthesia modulates the inflammatory response to surgery and may better allow the body to focus on fighting bacteria.
2.Spinal/epidural anesthesia may improve the body's ability to carry oxygen to tissue.
3.Spinal/epidural anesthesia may also provide excellent analgesia even after surgery.

"Dr. Chang's work is important in helping the medical community better identify solutions for reducing SSIs," said Dr. Sessler. "There is more research needed to better understand why spinal/epidural anesthesia may reduce such infections."