DOI: 10.1097/01.sa.0000185367.08599.89
,
Issn Print: 0039-6206
Publication Date: 2005/12/01
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Excerpt
Michela Camorcia, Giorgio Capogna, and Malachy O. Columb
(Anesthesiology, 102:646-650, 2005)
Department of Obstetric Anesthesia, Citta di Roma Hospital, Rome, Italy.
Doses of intrathecal opioid-local anesthetic mixtures are arbitrarily chosen. The analgesic efficacies of intrathecal ropivacaine, levobupivacaine, and bupivacaine for labor analgesia were compared to ascertain the analgesic potency ratios for these 3 drugs. An up-down sequential allocation model that estimates the minimum local analgesic dose for intrathecal local anesthesia was used. Ninety-seven nulliparous term parturients in spontaneous labor who asked for combined spinal-epidural analgesia were randomly assigned to 1 of 3 groups to be given 0.25% spinal ropivacaine, levobupivacaine, or bupivacaine. The initial dose of the local anesthetic drug was 2.5 mg, and the testing interval was 0.25 mg. The subsequent doses were determined by the response of the previous parturient. Efficacy was accepted if the visual analog pain score decreased from 10 mm or less on a 100-mm scale within 30 minutes. The minimum local analgesic dose was calculated by the method of Dixon and Massey. The intrathecal minimum local analgesic dose was 3.64 mg (95% confidence interval, 3.33-3.96 mg) for ropivacaine, 2.94 (2.73-3.16) mg for levobupivacaine, and 2.37 (2.17-2.58) mg for bupivacaine. The relative analgesic potency ratios were 0.65 (0.56-0.76) for ropivacaine/bupivacaine, 0.80 (0.70-0.92) for ropivacaine/levobupivacaine, and 0.81 (0.69-0.94) for levobupivacaine/bupivacaine. Marked trends existed for greater motor block with bupivacaine and levobupivacaine. A potential hierarchy of spinal bupivacaine > levobupivacaine > ropivacaine is suggested.
