Researchers at Taipei Medical University Hospital (Taiwan) used the Taiwanese Longitudinal Health Insurance Database to compare the risk of SSI within 30 days of surgery for patients receiving total hip or knee replacement under GA, versus those under epidural or spinal anesthesia; a total of 3,081 patients who underwent primary total hip or knee replacement from 2002 to 2006 were included in the study. Multivariate logistic regression and propensity score analyses were carried out to explore the relationship between method of surgical anesthesia and SSI occurring within 30 days of surgery.

The results showed that of the 3,081 sampled patients, 56 patients (1.8%) had 30-day SSIs; 33 of them had undergone GA (2.8% of all under GA), while 23 of them received epidural or spinal anesthesia (1.2% of all under epidural or spinal anesthesia). The researchers calculated that the odds of SSI in patients receiving total hip or knee replacement under general anesthesia were 2.21 times higher than those who had the same procedure under epidural or spinal anesthesia, after adjustment for the patient's age, sex, the year of surgery, comorbidities, surgeon's age, and hospital teaching status. The study was published in the August 2010 issue of Anesthesiology.

"Many anesthetics used in general anesthesia have been shown to compromise immunity responses,” said lead author Chuen-Chau Chang, M.D., M.P.H., Ph.D., and colleagues of the department of anesthesiology. "Anesthetic choices may impact a patient beyond the operating room and hospital stay which could increase in-hospital and postdischarge financial burdens.”

Among the possible reasons why spinal and epidural anesthesia demonstrated lower infection rates are that they modulate the inflammatory response to surgery and may better allow the body to focus on fighting bacteria; they may also improve the body's ability to carry oxygen to tissue, as well as provide excellent analgesia even after surgery.

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