Anesthesia (11)
Authors: Simpson R.S. , Macintyre P.E. , Shaw D. , Norton A. , McCann J.R. , Tham E.J. 
Published: September 2010

Epidural catheter tip cultures: results of a 4‐year audit and implications for clinical practice. (Royal Adelaide Hospital and University of Adelaide, Adelaide, Australia) Reg Anesth Pain Med 2000;25:360–367.

This study aimed to evaluate the clinical relevance of routine microbiological culture of epidural catheter tips after use in acute pain management, and to identify patterns of culture result with respect to both indications for, and duration of, epidural catheterization. Over a 4‐year period, when acute pain service (APS) protocol required epidural catheter tips to be sent for microbiological culture on removal, APS saw 1,810 patients who had received epidural analgesia. The records of the patients were reviewed. Culture results were available for 1,443 (79.7%) patients: 1,027 catheter tips (71.2%) were sterile, while 416 (28.8%) were positive for at least 1 type of microorganism. Clinically, no epidural space infections were identified. The highest positive culture rates were found from epidural catheters used in treatment of pain from fractured ribs or fractured pelves. The lowest incidences occurred in elective orthopedic and thoracic surgery. The proportion of epidural catheters with positive culture results steadily increased with the duration of catheterization, but there were no clinically significant differences for catheters left in situ for either 3 or 4 days. Conclude that a significant proportion of epidural catheter tips may be “culture positive” after removal. It is suggested that this probably represents colonization of the skin at the catheter insertion site and subsequent contamination of the catheter tip on removal of the catheter. The large number of “culture positive” tips in the absence of clinically identifiable epidural space infection suggests that routine culture of epidural catheter tips is clinically irrelevant in the vast majority of cases, and that it is not a good predictor of the presence of an epidural space infection.

Comment by Alan David Kaye, MD, PhD.

Clinically relevant epidural catheter‐induced infection is quite rare with the largest study on this topic revealing 1/505,000 catheter placements. This retrospective study involved the insertion of 1810 epidural catheters. At the time of insertion, full aseptic precautions were employed. When the catheters were removed, they were cultured and it was revealed that 28.8% were positive for at least 1 organism. This prevalence is relatively consistent with other published studies. The most common organism found was coagulase negative staphylococcus. Interestingly, not one of these patients developed an epidural abscess. The authors speculate that the relatively common prevalence of organism positive cultures was related to poor sterile technique at the catheter insertion site at the time of placement and/or removal. The authors conclude that epidural catheter contamination in the vast majority of cases is clinically irrelevant. In as much as epidural abscess can have vital clinical implications, it behooves the practitioner to adhere to strict sterile techniques even though the likelihood of infection is extremely low. Certainly, this study reinforces the fact that routine culture of epidural catheter tips is not a good predicator of epidural space infection.