Epidural Clonidine after Cesarean Section Appropriate Dose and Effect of Prior Local Anesthetic


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Abstract

Epidurally administered clonidine represents a new approach to postcesarena section pain therapy, yet the appropriate bolus dose and infusion to provide effective pain relief have not been defined. In addition, whether 2-chloroprocaine, a commonly used local anesthetic for intraoperative anesthesia, interferes with clonidine's analgesis, as it does with that of opioids, has not been examined. In this study, using a randomized, blinded design, 63 women received either bupivacaine or 2-chloroprocaine for epidural anesthesia for cesarean section and then received, upon request for analgesia in the recovery room, epidural clonidine 400 μg or 800 μg bolus, each followed by a 24-h infusion of 40 μg/h, or an equivalent volume bolus and infusion of saline. In the bupivacaine group, both clonidine doses produced equivalent analgesia, as determined by pain scores and time to first supplemental intravenous morphine request, and sustained analgesia was produced by clonidine infusion, as measured by need for supplemental morphine. In contrast, 2-chloroprocaine diminished analgesia from 800 μg by 21% and abolished analgesia from 400 μg clonidine. After 2-chloroprocaine, sustained analgesia from continuous clonidine infusion was present only in the group who had received 800 μg clonidine. Clonidine did not alter resolution of residual local anesthetic sensory blockade, as measured by 2− or 4-segment regression following either local anesthetic, but did prolong duration of motor blockade in women receiving bupivacaine. Clonidine produced small decreases in heart rate and blood pressure. One patient received iv fluids for hypotension; one had asymptomatic bradycardia resolving without therapy; and one had mild hypoxemia with snoring during clonidine-induced sedation, responding to supplemental oxygen. These results demonstrate a profound inhibition of clonidine-induced analgesia by 2-chloroprocaine solutions and suggest that a 400-μg bolus plus 40 μg/h is an appropriate initial regimen for epidural clonidine analgesia after bupivacaine anesthesia in this patient population.

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