THE EFFECTS OF EPIDURAL ROPIVACAINE AND BUPIVACAINE FOR CESAREAN-SECTION ON UTEROPLACENTAL AND FETAL CIRCULATION

Background: Ropivacaine is a new long-acting amide local anesthetic th at has been shown in animal studies to have less dysrhythmogenic and c ardiotoxic potential than bupivacaine. The intravenous administration of ropivacaine has not been associated with any detrimental effects on uterine blood flow in pregnant ewes. The purpose of this randomized, double-blind study was to examine the effects of epidural ropivacaine for cesarean section on blood now velocity waveforms in uteroplacental and fetal arteries with color Doppler ultrasound and to assess whethe r the block modified fetal myocardial function. Methods: Healthy partu rient women with singleton, uncomplicated pregnancies at term received 115-140 mg 0.5% ropivacaine (n = 11) or 0.5% bupivacaine (n = 10) in incremental epidural doses, The first ultrasound measurement was perfo rmed before injection of the study drug. Pulsatility indexes (PI) were derived for the blood now velocity waveforms of the maternal placenta l and nonplacental uterine arteries; the placental arcuate artery; and the fetal umbilical, middle cerebral, and renal arteries. The fetal h eart then was examined by echocardiography. The PI of the maternal ute rine arteries and the fetal umbilical artery were measured 5 min after the injection of the local anesthetic. When sensory analgesia had rea ched the T6-T4 level, the ultrasound measurement was repeated with the same methods and targets as in the baseline measurement. Results:Both drugs provided adequate surgical anesthesia for cesarean section. In the bupivacaine group, the PI values for the maternal placental and no nplacental uterine arteries increased significantly 5 min after the ma in dose (P = 0.01, P = 0.002) and when sensory analgesia had reached t he T6-T4 level (P = 0.004, P = 0.01) as compared with the baseline mea surement. Simultaneously, the PI in the fetal middle cerebral artery d ecreased significantly (P = 0.02). The PI for the maternal uterine art ery increased significantly (P = 0.01) after ropivacaine administratio n but only on the nonplacental side and not until sensory analgesia ha d reached the T6-T4 level. No effect on the Doppler indexes obtained f rom the umbilical artery was observed in either group, There were no s ignificant differences relative to baseline values in any fetal myocar dial measurement or in any ultrasound measurement between the groups, Neither drug had any detrimental effect on Apgar scores or umbilical c ord acid-base status. None of the neonates' conditions was markedly de pressed according to neurobehavioral testing. Conclusions: Within this small study, epidural 0.5% ropivacaine for cesarean section did not c ompromise the uteroplacental circulation in healthy parturient women w ith uncomplicated pregnancies, It provided surgical anesthesia that wa s equally effective as that provided by 0.5% bupivacaine.