Purpose: When used intraoperatively, mepivacaine can produce a satisfactory sensory block. However, insufficient informaton is available concerning the factors that affect the speed of nerve blockade with epidural analgesia. The optimal rate of injection of mepivacaine has not been determined. We examined whether the speed of epidural infusion of mepivacaine affects the speed of nerve blockade. Methods: Forty patients, physical status ASA I-II, scheduled for gynecological abdominal surgery, were enrolled in this double blind randomized trial. A catheter was inserted 4 cm in the epidural space in the midline at L1-L2. Three minutes after a test dose of 2 mL plain 1% mepivacaine over four seconds, 8 mL were injected epidurally at a rate of 1 mL·sec-1 (fast group) or 0.05 mL·sec-1 (slow group). Sensory and motor blockade, blood pressure, and heart rate were assessed at five, ten, and 15 min after the epidural injection. Results: There was a significant difference in the spread of sensory blockade at five minutes after the epidural injection between the two groups, but not at ten and 15 min. Blood pressure decreased at five and ten minutes, recovered at 15 min in the fast group, and remained stable in the slow group. Conclusion: Rapid injection of mepivacaine in the epidural space produced a more rapid onset of epidural block than slow injection, but there was no difference in the final extent of the block.
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