Repeated failure of epidural analgesia: an association with epidural fat?

BACKGROUND AND OBJECTIVES: To report the case of a patient who experienced repeated failed epidural analgesia associated with an unusual amount of fat in the epidural space (epidural lipomatosis). CASE REPORT: A 44-year-old female presented for an elective small bowel resection. An L(1-2) epidural catheter was placed for postoperative analgesia. The patient gave no indication of having pain at the time of emergence from general anesthesia or in the first 2 hours in the recovery room. Assessment of the level of hypoesthesia to ice while the patient was comfortable in the recovery room suggested a functional epidural catheter (cephalad level of T(10)). Two hours after admission to the recovery room the patient began to complain of increasing pain. Another 6 mL 0.25% bupivacaine was administered via the catheter. The patient's pain decreased, but remained substantial, and there was minimal evidence of sensory block above the T(10) level. Subsequently, a T(10) epidural catheter was placed. Testing confirmed proper placement of the catheter in the epidural space at the T(10) level. A test dose of 5 mL 0.25% bupivacaine resulted in prompt and complete relief of the patient's pain. However, the level of hypoesthesia to ice did not exceed the T(10) level. Approximately 1 hour later the patient complained of increasing discomfort again. There was no evidence of any sensory block, and there was no response to a bolus of 8 mL 1% lidocaine. A thorough examination of the patient did not suggest any cause for the pain other than a malfunctioning epidural catheter. A third epidural catheter was placed at the T(8-9) level. This catheter was again confirmed to be in the epidural space with a test dose of 10 mL 0.5% bupivacaine. The level of hypoesthesia to ice was restricted to a narrow bilateral band from T(7)-T(9). Analgesia failed 2 hours later. The epidural catheter was removed and the patient's pain was subsequently managed with intravenous patient-controlled analgesia (PCA) morphine. A magnetic resonance imaging (MRI) scan revealed extensive epidural fat dorsal to the spinal cord from C(5)-C(7) and from T(3)-T(9). An imaging diagnosis of asymptomatic epidural lipomatosis was established.
CONCLUSION: We have described a case of repeated failure of epidural analgesia in a patient with epidural lipomatosis.