Hemodynamic Effects of Ephedrine, Phenylephrine, and the Coadministration of Phenylephrine With Oxytocin During Spinal Anesthesia for Elective Cesarean Delivery

Comparison of metaraminol, phenylephrine and ephedrine in prophylaxis and treatment of hypotension in cesarean section under spinal anesthesia

“…30 Dyer et al, in a study evaluating pregnant women undergoing cesarean section under spinal anesthesia through minimally invasive cardiac output monitors (LiDDCO and BioZ) who received ephedrine or phenylephrine, showed that, after spinal anesthesia, the pregnant women had a marked decrease in systemic vascular resistance, with a compensatory increase in cardiac output, and concluded that low doses of phenylephrine are able to restore the systemic vascular resistance and cardiac output to baseline values. 31 Auler et al 32 who also assessed maternal hemodynamic changes through minimally invasive monitoring of pregnant women undergoing cesarean section under spinal anesthesia and who received metaraminol to control blood pressure, reported a decrease in systolic volume, offset by increased heart rate, but did not observe significant changes in mean arterial pressure and systemic vascular resistance, and speculated that these results occurred because of more rapid and effective correction of mean arterial pressure by the administration of metaraminol.…”

The use of uterotonic drugs during caesarean section

“…Early studies used transthoracic bioimpedance and thermodilution technology. 9,10 More recently, beat by beat pulse wave form monitors, [11][12][13] and additional studies using transthoracic bioimpedance, 12,14 have provided a clinical picture of peripheral vasodilatation, hypotension, and increased cardiac output mediated by an increase in heart rate and stroke volume. Pulmonary artery pressures are markedly increased and stay so for at least 10 min after a bolus of 10 IU during general anaesthesia.…”

“…24 Co-administration of phenylephrine with oxytocin has been shown to obtund the peripheral vascular effects, but there was some overshoot of the effects of phenylephrine, suggesting that administration of phenylephrine immediately before oxytocin may be more effective. 12 In view of the multiple side effects of oxytocin, it is desirable to administer the lowest possible effective dose in the most stable manner. The dose and rate of intravenous infusion of oxytocin after delivery during CS remain controversial.…”

Minimally- and non-invasive assessment of maternal cardiac output: go with the flow!

“…Haemodynamic responses to spinal anaesthesia and oxytocin were also recorded. CO changes correlated with HR changes after vasopressor administration, emphasizing the importance of HR as a surrogate indicator of CO. 93 Langesaeter et al performed an elegant study using the LiDCO Ò technology to establish the optimal combination of spinal bupivacaine and sufentanil with a peripheral phenylephrine infusion in order to preserve maternal haemodynamic indices. 94 Another study by this group successfully investigated the haemodynamic effects of oxytocin in women with severe preeclampsia using the LiDCO Ò monitor.…”