[Subdural location of a catheter. A complication of peridural anesthesia].

A case of an involuntarily placed subdural catheter (between arachnoid and dura) is described. The catheter was thought to be in the epidural space. It was placed at T9/10 in order to achieve postoperative epidural analgesia in a patient with colonic surgery. Administration of 4 ml bupivacaine 0.5% was followed by segmental analgesia (left: C7 to T9, right: T2 to T8) 10 min later. The systolic blood pressure fell from 85 to 50 mmHg. No motor block was detectable. After 150 min remission of analgesia was complete. All effects were reproducible. Using 1.3 ml of a radiopaque fluid, a spinal X-ray film showed a typical subdural picture with radiopacity detectable on the left from C8 to T8 and on the right from T1 to T7. An additional 2.7 ml did not visualize the lumbar subdural space as well. No radiopaque fluid entered the epidural or intrathecal space. It may be that accidental subdural catheter placement in regional anesthesia is not as rare as it was thought to be a few years ago. There is at present no available epidural technique that guarantees the avoidance of this complication. In addition, the symptoms of 'subdural analgesia' vary to a great extent. Therefore, the diagnosis can only be verified by X-ray examination. If patients with epidural analgesia are supervised with care and uncommon dose responses are recognized, subdural catheter placement will not lead to a severe and dangerous situation for the patient.