Epinephrine added to a lumbar epidural infusion of a small-dose ropivacaine-fentanyl mixture after arterial bypass surgery of the lower extremities

Background: The addition of epinephrine (2 mug . ml(-1)) to a thoracic epidural infusion of an opioid-local anesthetic mixture improves analgesia. Here, we studied whether epinephrine could improve analgesia also at lumbar level, when added to an epidural infusion of a low-dose ropivacaine-fentanyl mixture after arterial bypass surgery of the legs. Methods: Patients in group RFE ( n = 21) received a postoperative epidural infusion containing ropivacaine (1 mg . ml(-1)), fentanyl (2 mug . ml(-1)), and epinephrine (2 mug . ml(-1)). Patients in group RF ( n = 25) received a similar infusion without epinephrine. The infusion speed was 1 ml . 10 kg(-1) . h(-1). The infusion was scheduled for 48 h. Results: Epinephrine did not reduce the need for rescue pain medication. Visual analog scale scores ( VAS) for pain at rest were low and similar in the groups. Pain intensity was stronger during leg movement [ mean VAS 1.5 - 2.6 ( range 0 - 9)], but it was not affected by the coadministration of epinephrine. The groups did not differ concerning frequency and severity of side-effects. Epinephrine did not reduce fentanyl plasma concentrations. Ropivacaine concentrations were slightly lower in group RFE only in the samples 6 h from the start of the infusion, but not anymore on the first and second postoperative day. Conclusion: In the dosage used here, epinephrine did not improve epidural lumbar analgesia. Different distances from the epidural application site to the alpha2-adrenergic receptors of the spinal cord, and differing epinephrine dose requirements may explain why epinephrine as an additive improves epidural analgesia at thoracic, but not at lumbar level.