Bacterial colonization and infection of epidural catheters: a prospective study of incidence and risk factors in surgical patients

Infection of the epidural space is a rare but serious complication of catheter placement. The purpose of the present study was to determine the incidence of bacterial colonization of epidural catheters, the co-relation between colonization and infection and to identify the risk factors associated with colonization.Aprospective observational trial was carried out on 272 adult patients receiving epidural catheterization for anaesthesia and post-operative analgesia. Patients undergoing a variety of surgical proce-dures (abdominal, thoracic, urological, orthopaedic, gynaecological and obstetric) both elective and emergency were recruited. The tips of epidural catheters after removal were sent aseptically for culture. Of 261 tips sent for culture 11 (4.2%) showed positive culture, the most prevalent microorganism being Staphylococcus epidermidis. None of the patients had signs and symptoms of local or epidural space infection. Twelve potential risk factors were entered in the step-wise logistic regression analysis to identify factors associated with catheter colonization. Out of these only the duration of catheterization (P< 0.01, odd ratio 3.39, 95% confidence interval 0.12-1.5) was found to be significant. Summarizing the results, the incidence of bacterial colonization was 4.2% with no case of epidural space infection. The chances of colonization increased with duration of placement beyond 96 hours and this was found to be a potential risk factor for colonization but not infection. The positive cultures did not equate with infection.