• Yehuda Ginosar, Carolyn F Weiniger, Vladimir Kurz, Anatoly Babchenko, Meir Nitzan, and Elyad Davidson.
• Department of Anesthesiology and Critical Care Medicine, Hadassah Hebrew University Medical Center, POB 12000, Jerusalem 91120, Israel. yginosar@netvision.net.il
• Can J Anaesth. 2009 Mar 1;56(3):213-21.

PurposeWe tested the hypothesis that the development of sympathectomy-mediated vasodilatation is dependent on the concentration rather than the dose of epidural local anesthetic administered.MethodsSixty subjects receiving lumbar epidural bupivacaine were randomised to one of three groups: A: 10 ml 0.5% (50 mg); B: 10 ml 0.25% (25 mg); and C: 40 ml 0.0625% (25 mg). Groups A and B had equal volume but a twofold difference in drug dose, while groups B and C had equal drug dose, but a fourfold difference in drug volume. At baseline and 5, 10, and 20 min following epidural bupivacaine administration, we assessed the following indices of sympathectomy: pulse oximeter perfusion index in the toe and finger, skin temperature in the toe and finger, and mean arterial pressure. We also assessed sensory level (pinprick, cold, and light touch) and motor block.ResultsThere was an increase in the pulse oximeter perfusion index by 20 min of 280%, 303%, and 59% in groups A, B, and, C, respectively. There was a significant sympathectomy-mediated vasodilatation in the toe for both groups A (P = 0.002) and B (P < 0.001) but not C (P = 0.22). Vasoconstriction in the finger was observed in group A only (P = 0.015) but not in group B (P = 0.09) or group C (P = 0.20). There were similar blood pressure changes and similar sensory changes in all groups. The intensity of motor block increased with increasing drug concentration.ConclusionsOur observations suggest that drug concentration is more important than drug dose in determining the degree of sympathectomy following lumbar epidural local anesthesia.

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