Continuous mini-infusion of bupivacaine into the epidural space during labor. Part I: Radiographic visualization of the epidural catheters.

Two groups, each consisting of 20 parturients, were given a continuous infusion of 0.25 per cent bupivacaine into the epidural space for pain relief, after test and loading doses. The analgesic effect was registered during labor. After delivery the course of the catheters in the epidural space was investigated radiologically. In the first group long catheters (mean 16.5 cm from the skin surface) and in the second group short catheters (mean 10.5 cm) were used. The medial approach in the epidural space was varied between the first and second lumbar interspaces. The relationship between the position of the catheter tip and the degree of analgesia was also studied. In two mothers with fetus mortuus ante partum, the spread of a radiopaque dye solution was followed during labor. Through the force of gravity and the mothers position, the spread of solution covered three segments within 30 minutes. It was concluded, that slow infusion of local anesthetic solution gives satisfactory pain relief if the catheter is inserted into the first lumbar interspace to a depth of 10--12 cm from the skin surface ending close to the Th12 level. Gradual raising of the mother from the supine to the semirecumbent position and regular change of sides during mini-infusion is important for an even spread of the analgesic solution and analgasia.