[Routine postoperative epidural analgesia. X-ray control of epidural catheter position and prevention of the spread of epidural contrast media].

In the last few years epidural analgesia with bupivacaine and/or opioids has become an important technique in the therapy of postoperative pain. Using bupivacaine only 2-20% of the patients are treated without sufficient success. To ascertain and evaluate the underlying reasons for this, we prospectively investigated 51 patients routinely, and 6 patients with an insufficient analgetic effect from a group of 212 patients, by means of epidurography. All patients were treated mainly with bupivacaine. The observed and documented radiographic data were compared with the individual analgetic results. METHODS. All investigations were performed within 24 h after placing the catheters. The contrast agent was injected under radiographic guidance in two different positions, and the end of the distribution was documented in the anterior-posterior ray path. In group I (n = 26) the catheter position and the distribution of the contrast medium with 3.0 ml iopamidol were documented. In group II (n = 25) the catheter position was documented in the same way, but the distribution was documented for the stepwise-injected contrast medium (3.0 ml + 2.0 ml + 3.0 ml). As a result of these findings we changed our epidural catheter placement concept in the following patients (group III, n = 212), and performed radiographic examinations in patients with a therapy failure only (group IIIa, n = 6). Instead of placing the catheter postoperatively mostly lumbal in a lateral position, we now placed them preoperatively, in the sitting position, as near as possible to the centre of the segments to be treated. RESULTS. Only 27 patients demonstrated an ideal catheter position and a typical contrast medium distribution. Three of these patients still could not be treated successfully. In 12 patients the spread of the contrast medium was inhomogeneous, and in 5 patients the contrast medium was found on one side of the epidural space only. Half of these 17 patients (n = 9) needed supplementary therapy. Surprisingly, 4 of 8 patients with a paraepidural catheter position were treated with success. DISCUSSION. Effective bupivacaine therapy by epidural catheter injections constitutes no striking evidence for a correct epidural catheter position. If the catheter lies in the epidural space, the actual therapeutic effect of bupivacaine therapy is determined mainly by the distribution of the substance. The epidural position of the catheter--central or lateral in the epidural space--seems, however, not to be particularly important. If high-quality analgesia is to be achieved with bupivacaine alone, or in combination with an opioid, the catheter should usually be placed near to, or better into the centre of the segments to be treated. The results demonstrate that in the case of failure of epidural catheter therapy, epidurographic examinations are very helpful in ascertaining and evaluating the underlying reasons for this failure and in coming to a logical decision for changing the concept.