Metaraminol 2.5mg/5ml solution for injection ampoules

IntroductionPhenylephrine infusion is widely endorsed by guidelines as the preferred prophylactic drug for spinal hypotension in patients undergoing caesarean delivery; however, clinical practice continues to show marked variability in the selection of vasopressor drugs. To address this, we aimed to synthesise current evidence from randomised controlled trials comparing vasopressor infusions for various feto-maternal outcomes in normotensive adult patients undergoing caesarean delivery.MethodsRandomised controlled trials evaluating maternal and fetal outcomes associated with prophylactic vasopressor infusion were identified through comprehensive database searches. Primary outcomes were the incidence of maternal hypotension and umbilical artery base excess. Secondary outcomes comprised maternal and fetal parameters including: umbilical artery and vein pH; umbilical vein base excess; Apgar scores at 1 min and 5 min; and incidence of maternal intra-operative nausea and vomiting, bradycardia, tachycardia and hypertension.ResultsFifty-five trials involving 5487 patients undergoing caesarean delivery under spinal or combined spinal and epidural anaesthesia using a variety of vasopressor infusions were included in the final analysis. Four drugs-metaraminol, noradrenaline, phenylephrine and adrenaline-were judged to be 'definitely superior' to control (no active vasopressor infusion) for the prevention of hypotension. Umbilical vessel analyses indicated that mephentermine and metaraminol provided superior preservation of both umbilical arterial and venous acid-base balance.DiscussionCurrent evidence suggests that continuous infusions of α-agonists with mild β-activity (e.g. noradrenaline, metaraminol) are preferable to mixed adrenergic agonists such as ephedrine for preventing maternal hypotension. While these findings reinforce existing recommendations for maternal haemodynamic management, the evidence base for fetal outcomes remains limited.

Abstract licence: CC BY-NC-ND