Photoplethysmographic evaluation of sympathectomy during lumbar epidural analgesia: A randomized comparison of 0.125% ropivacaine and 0.125% levobupivacaine.

Background: There are no data on the difference between the impact of ropivacaine and levobupivacaine on sympathetic nerve fibers during central neuraxial blocks. We hypothesized that there is no difference in the degree of sympathectomy between the two drugs during lumbar epidural analgesia for labor pain.

Methods: Sixty healthy parturients were randomized to the type of local anesthetic-opiod solution administered in the epidural space: 10 mL of 0.125% ropivacaine + 100 mcg of fentanyl or 10 mL of 0.125% levobupivacaine + 100 mcg of fentanyl. After the baseline measurement, photoplethysmography signal from the first toe of the leg was recorded 5, 10 and 20 minutes after administration of epidural analgesia.

Results: Area under the curve and the pulse transit time of the toe photoplethysmography increased in both groups during the first 20 minutes after administration of epidural analgesia (P < 0.001 for both parameters in both groups). No difference in the degree of sympathectomy was found between the groups for the area under the curve. The difference in the change of the pulse transit time suggests that the two local anesthetics might differ in the degree of sympathectomy (P = 0.024).

Conclusion: 0.125% ropivacaine and 0.125% levobupivacaine do not differ in the terms of sympathectomy-mediated side effects of the epidural block for labor analgesia. However, the photoplethysmography findings suggest a certain difference in the degree of sympathectomy between the two local anesthetics.