Abstract: Objective Comparing the effects of combinations of methoxamine and ephedrine in varying proportions on preventing hypotension and maternal fetal to evaluate the curative effects of drug combinations in different proportions during combined spinal and epidural anesthesia(CSEA) for cesarean section. Methods One hundred and fifty parturients undergoing CSEA for elective cesarean delivery were randomly divided into five groups with 30 each parturients to receive intravenous administration of combinations of methoxamine and ephedrine in different proportions, respectively. Assuming that 2 mg methoxamine to be approximately equipotent to 8 mg ephedrine, five combinations drugs were infused in differents proportions which were potency equivalent of 100%, 75%, 50%, 25% or 0 of methoxamine and 0, 25%, 50%, 75% or 100% of ephedrine, respectively. Changes of maternal homodynamic and umbilical arterial blood gas analysis were measured. Infant Apgar score and incidence of maternal nausea and vomiting were also recorded. Results With the decreased proportion of methoxamine and increased ephedrine in these groups,the incidences of hypotension[group 1 (3%), group 2(10%), group 3(7%), group 4 (13%), group 5(30%)] showed a rising trend(P<0.05). The increased of nausea/vomiting of group 2 and 3 was lower than other three groups [(group 1 7%), group 2(3%), group 3(0%), group 4(10%), group 5(23%)](P<0.05). The study showed a downtrend of the incidence of umbilical arterial fetal hemoglobin from group 1 to group 5[group 1 93(91-98)%, group 2 89(86-91)%,group 3 88(85-91)%、group 4 85(83-89)%、group 5 81(78-84)%](P<0.05) and and a uptrend of partial pressure of carbon dioxide[group 1 49(46-54) mmHg、group 2 51(45-56) mmHg, group 3 53(47-57) mmHg, group 4 55(50-59) mmHg, group 5 56(51-59) mmHg(1 mmHg=0.133 kPa)](P<0.05). Conclusions Combinations of methoxamine and ephedrine infused to maintain arterial blood pressure during CSEA for cesarean delivery in the proportion decreased of ephedrine and the increased proportion of methoxamine exhibits a strengthened control of maternal hemodynamic. The study shows that the range of combinations drugs from 0.375 g/L methoxamine: 0.5 g/L ephedrine to 0.25 g/L methoxamine: 1 g/L ephedrine can produce more beneficial effect on the fetus.
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