Is postoperative intrathecal catheter use associated with central nervous system infection?

Continuation of intrathecal anesthesia into the postoperative period has been limited by important safety concerns. Principal among these has been the assumption that extended intrathecal therapy leads to spinal (epidural and intrathecal) space infections. To address the role of extended intrathecal catheter therapy as a cause of infections, we cultured all intrathecal catheters used to provide postoperative analgesia.

All intrathecal catheters were inserted in the operating room using sterile technique. The catheters were used either for the duration of the patients stay in the intensive care unit or until they were no longer judged to provide a therapeutic advantage. They were removed without skin preparation. The distal 2-3 cm of the catheters was cultured using semiquantitative culture methods. Results were divided into four groups: group 1, negative culture results; group 2, ten or fewer colonies of growth; group 3, more than 10 colonies on initial plates and/or growth from broth cultures; and group 4, any bacterial growth, along with evidence of local or central nervous system infections.

Cultures were obtained from 139 patients with a mean indwelling catheter time of 66.1 h. Group 1 (102 patients) had a mean indwelling duration of 55 h. Group 2 (26 patients) and group 3 (11 patients) had significantly longer indwelling duration (83.2 h P = .0023, 129.6 h P = < .0001, respectively) than group 1. Cultures of cerebrospinal fluid obtained simultaneously with catheter cultures in 9 cases (5 in group 2 and 4 in group 3) showed no growth. No patient had evidence of local or central nervous system infection. Difficulty of catheter placement (number of attempts made and the number of levels explored), antibiotic administration, the composition of the postoperative infusions and the number of catheter breaks in the postoperative period were similar in each group. With the exception of two catheters in group 3, (cultured at 49 and 54 h), significant bacterial growth (more than ten colonies) was observed only after more than 96 h of indwelling duration.

Application of semiquantitative culture methods assisted in explaining the results seen in group 2 as secondary to contamination of the catheter that occurred on removal. Higher numbers of bacteria (group 3) may define a population at increased risk for infectious complications. The results of this study do not absolutely resolve the issue of infectious risk associated with postoperative intrathecal catheter use, nor do they define a safe period beyond which the risk of continued catheter use would be unacceptable. However, it appears that limited periods of use (96 h or less) is not associated with either frequent local or spinal infections. Semiquantitative culture methods may help identify individuals (with catheter cultures yielding more than ten colonies) at increased risk for infectious complications and in need of closer observation.