Spread of injectate in an interrupted epidural space

Sondra E. Shields, David W. Polly

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Introduction. The epidural space has been studied radiographically to determine the anatomy of the epidural space in adults and infants (1,2), the optimal catheter insertion length (3), spread of injectate using a paramedian vs. midline approach (4), spread of injectate using multi-orifice vs single orifice epidural catheters (5), and causes of unilateral spread (6,7). However, to date, no characterization has been published of the spread of injectate in an interrupted epidural space such as that following posterior spinal surgery for scoliosis or spondylolisthesis. Methods. Seven subjects undergoing posterior spinal fusion for scoliosis (4 idiopathic, 1 congenital) or for spondylolisthesis (2) were studied. Age range was 8 to 34 years. There were 5 males and 2 females. Consent was obtained for catheter placement intraoperatively as per routine surgical postoperative pain control protocol. A 20 gauge closed tip multi-orifice Perifix catheter was placed by the operating surgeon in the epidural space at the end of the surgery. The catheter was placed through a paramedian approach into the surgical field. Then under direct vision, it was passed under the lamina in the upper end of the incision. It was advanced approximately two levels and an attempt was made to keep it in the midline. The wound was then closed. Ten cc's of iopamidol 41% was injected under fluoroscopy, and the extent of epidural spread was evaluated. Results. Contained epidural spread occurred in six out of seven patients, with the injectate outlining the epidural space in both anterior/posterior and lateral views. Bilateral nerve sleeves could be seen filling for several segments cephalad to the catheter orifice. In one out of seven patients, the injectate was noted to extravasate into the paravertebral tissue dorsally over a laminectomy defect. In two patients, the contrast initially filled unilaterally, suggesting the catheter was not in the midline. With additional volume (of the initial 10 cc's), the contrast spread bilaterally. Excellent postoperative pain relief was achieved in this group of patients. Discussion. These results suggest that epidural catheters placed into an interrupted epidural space spread normally in the majority of patients. The patients can consequently benefit from analgesia provided by epidural catheters. In our clinical practice for the last 3 years we have seen no infections or complications related to the use of these catheters in approximately 200 such patients. The catheters are typically left in place for 3-4 days and the patients are able to ambulate with them in place.

Original languageEnglish (US)
Number of pages1
JournalRegional Anesthesia
Issue number2 SUPPL.
StatePublished - Dec 1 1997

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