Epidural infusion pressure in degenerative spinal disease before and after epidural steroid therapy

The analgesic mechanism of epidural steroids in reducing pain associated with degenerative spinal disease (DSD) is poorly understood. We report increased inline epidural infusion pressure in patients with DSD and assess whether this phenomenon is affected by administration of an epidural steroid injection. We collected data during epidural placement for routine surgery or epidural steroid therapy. Using a 17-gauge Tuohy needle, with patients in the right lateral decubitus position, loss of resistance to 2 mL of saline identified the epidural space. Two minutes later the needle was attached to saline-filled tubing connected to a pressure transducer (Baxter PX 260 pressure monitoring kit with Truwave TM disposable pressure transducer). In the first part of the study, 4 successive boluses of 3 mL of local anesthetic were administered at a rate of 6 mL/min to 15 patients (age 47 +/- 6 yrs) with radicular back pain and magnetic resonance imaging (MRI) or computed tomography (CT) evidence of DSD, and to 8 control patients with no history of back pain (age 44 +/- 5 yr) while inline epidural infusion pressure was measured. In the second part of the study 44 patients with low back pain and MRI or CT evidence of DSD presenting to the pain clinic were infused with 8 mL of 0.125% bupivacaine and 40 mg of methylprednisolone (20 mg/mL) at a rate of 6 mL/min while inline epidural infusion pressure was measure and recorded. This was repeated 3 wk later. Initially, DSD patients had significantly increased infusion pressures over normals, which most likely reflects outflow resistance or obstruction. A significant decrease in inline epidural infusion pressure was observed after epidural steroid treatment. This change in pressure may indicate efficacy from epidural steroid injection.

During injection into the epidural space we observed increased resistance in patients with degenerative spinal disease. This resistance was significantly less when measured 3 wk after an epidural steroid injection. This change in pressure may indicate efficacy from epidural steroid injection.