Effect Of Varying Proportion Of Methoxamine And Ephedrine Combinations In Parturients And Fetus During The Cesarean Section

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:(1)One hundred and fifty ASA physical status 1 and 2 women with term singleton pregnancies undergoing CSEA for elective cesarean delivery were randomized allocated to five groups with 30 each.(2)We allowed patients to rest undisturbed in the left tilted supine position for several minutes and standard noninvasive monitoring was applied to patients,during which BP and HR was measured every 1-2 min. Baseline SBP and HR were calculated as the mean of the three recordings.(3)We induced spinal anesthesia in the left lateral position. After skin infiltration with lidocaine, a 25-gauge pencil-point needle was inserted at what was estimated to be the L2-3 or L3-4 vertebral interspace and hyperbaric 0.5% bupivacaine(2.2~2.4 ml)were injected intrathecally. We then returned the patient to the tilted supine position.(4)Assuming methoxamine 2 mg to be approximately equipotent to ephedrine 8mg,the groups contained the proportional potency equivalent of 100%、75%、50%、25% or 0 of methoxamine and 0、25%、50%、75% or 100% of ephedrine, respectively.(5)The vasopressors were infused using a syringe pump connected to the IV cannula using a three-way stopcock. Each group receive an IV infusion of methoxamine and ephedrine combination in one of five different proportions. Parturients received infusion of 3 ml different proportion of vasopressors combinations at a constant rate of60ml/h.(6)BP was measured at 2-min intervals beginning 1 min after spinal injection and end by 15 min.(7)Apgar scores were assessed 1 and 5 min after delivery.(8)The changes of maternal homodynamic, umbilical arterial blood gas and infant Apgar score were measured. The incidence of maternal nausea and vomiting were also recorded.Results:(1)With the decreased proportion of methoxamine and increased ephedrine in these groups, the time to the minimum recorded SBP was different among groups(P<0.001)and there was a significant trend from group 1 to group 5 for intrathecal injection-minimum BP interval to be shorter(P<0.001).There was difference overall in the incidence of hypotension among groups(P=0.020), the test for trend showed that there was a significant trend from group 1 to group 5 for the incidence to increase(P<0.05). The increased of hypertension of group 4 and 5was higher than other three groups( P<0.05).The number of systolic blood pressure above or below baseline increased.(2)The incidence of nausea or vomiting was different among groups(P=0.015)and the increased of nausea/vomiting of group 2 and 3 was lower than other three groups(P<0.05).( 3) The minimum and maximum recorded HR was different among groups( P<0.05), there was no difference among groups in the incidence of bradycardia(P=0.463).(4)All Apgar scores were ≥8 at 1 min and ≥9 at 5 min.(5)For UA blood, p H, BE, and Hb were no different among groups(P=0.265,P=0.174,P=0.186)and PCO2 、PO2 and oxygen content were different among groups(P<0.05). The test for trend showed that there was a significant trend from group 1 to group 5 for the incidence of umbilical arterial oxygen content decreased(P<0.05)and PCO2 increased(P<0.001).Conclusion:(1)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.(2) Through the umbilical cord blood gas and acid-base balance, fetal oxygen supply and demand situation analysis shows that the range of combinations drugs from0.375 mg/ml methoxamine:0.5 mg/ml ephedrine to 0.25 mg/ml methoxamine:1 mg/ml ephedrine can produce more beneficial effect on the fetus.