Comparison of the Efficacy of Continuous Metaraminol Infusion Versus Continuous Norepinephrine Infusion for the Prevention of Hypotension During Cesarean Section Under Spinal Anaesthesia. A Randomised Controlled Trial.

January 15, 2026 updated by: Adamantia Gkaniou, Aretaieion University Hospital

Prevention of Hypotension During Elective Cesarean Section Under Spinal Anaesthesia With Fixed-rate Metaraminol Infusion Versus Fixed-rate Norepinephrine Infusion: A Double-blind Randomised Controlled Clinical Trial.

The aim of this double-blind randomised study will be to compare a fixed-rate prophylactic metaraminol infusion to a fixed-rate prophylactic norepinephrine infusion during elective cesarean section under combined spinal-epidural anaesthesia.

Study Overview

Status

Not yet recruiting

Conditions

Intervention / Treatment

Detailed Description

Spinal anaesthesia is the anaesthetic technique of choice for elective cesarean section.

Spinal anaesthesia can be complicated by hypotension, with incidence exceeding 80% occasionally. Hypotension can lead to nausea, emesis and a subjective feeling of discomfort due to cerebral hypoperfusion. If left untreated, severe or sustained hypotension can lead to decreased uteroplacental flow and fetal distress of premature or compromised fetuses while severe complications to the parturient might ensue, such as loss of consciousness, aspiration, apnea or cardiac arrest.

Prophylactic vasoconstrictor infusion is an effective strategy for preventing maternal hypotension during regional anaesthesia. Phenylephrine is widely used because it acts quickly and causes less neonatal acidosis than ephedrine, but high doses may reduce maternal cardiac output. Norepinephrine and metaraminol, a sympathomimetic amine that acts both directly and indirectly, mainly by stimulating alpha-1-adrenergic receptors, with a weak effect on beta-receptors, have emerged as potential alternatives. While the optimal norepinephrine infusion dose has been defined in several studies, research on metaraminol remains limited, with insufficient data on its ideal dosing and efficacy in obstetrics. Most comparative studies evaluate metaraminol against phenylephrine-some suggesting better fetal acid-base outcomes-but no studies directly compare metaraminol with norepinephrine. Further research is therefore needed before metaraminol can be routinely recommended in obstetric anaesthesia.

This study will include pregnant adults who are normotensive, without complications, with a single pregnancy, who are not in active labor, and who are scheduled to undergo an elective cesarean section at the Gynecology-Obstetrics Clinic of Aretaieion Hospital.The study will use randomized, concealed allocation to assign participants to receive either metaraminol or norepinephrine infusions. Study group allocation will take place according to a computer-generated sequence of random numbers. A non-involved healthcare professional will reveal each participant's assignment, and a nurse will prepare identical 50 mL syringes labeled "study infusion," containing the drug at concentrations that deliver either 100 µg/min (200 µg/mL at 30 mL/h) of metaraminol or 4 µg/min (8 µg/mL at 30 mL/h) of norepinephrine. The anaesthesiologist, patient, and data analyst will remain blinded to group allocation.

All parturients will receive standard pre-anesthetic evaluation and standard hemodynamic monitoring will be applied. Next, on the hand opposite the one with the cuff for measuring NIBP, a special finger cuff connected to the Edwards Lifesciences ClearSight system will be placed on the index, middle, or ring finger. The ClearSight system from Edwards Lifesciences is a non-invasive medical system that allows continuous monitoring of blood pressure (cBP), as well as a range of other hemodynamic parameters such as cardiac output (CO), stroke volume (SV), and systemic vascular resistance (SVR).

Baseline systolic arterial pressure will be considered the average of three consecutive measurements that will not differ more than 10% among them.

All parturients will have a peripheral intravenous catheter placed in the upper extremity after baseline hemodynamic measurements are recorded. The peripheral venous catheter in the arm without the cuff will be connected via a three-way stopcock and a small-volume tube to an infusion syringe placed in an electronic infusion pump in standby mode. The syringe will contain the corresponding vasoactive drug "study infusion." At the same time, infusion of Ringer/Lactate solution at a dose of 3 mL/kg/h will begin through the study infusion line (pre-loading) before the regional procedure.

A standard spinal anaesthetic consisting of ropivacaine 0.75% 1.8 mL plus fentanyl 10 μg will be administered in the left lateraL position at the L3-4 or L4-5 vertebral interspace. The study infusion medication (either metaraminol or norepinephrine, depending on group allocation) will be started at the same time cerebrospinal fluid is obtained, immediately before injection of spinal medications. After the intrathecal injection, patients will placed in the supine position with a left lateral tilt to provide left uterine displacement and to prevent aortocaval compression. The spinal sensory level will be tested bilaterally to ensure a T4 dermatomal level before surgical incision.

Hemodynamic parameters [systolic blood pressure (SAP), diastolic blood pressure (DAP), mean arterial pressure (MAP), heart rate (HR), cardiac output (CO), stroke volume (SV), and systemic vascular resistance (SVR)] will be recorded by a specially trained, experienced anaesthesiologist at specific time points during the procedure: baseline (T0), initiation of the study drug infusion (T1), placement in the supine position after subarachnoid administration (T2), sympathetic blockade at the T4 level (T3), start of surgery (T4), delivery of the newborn (T5), 5 minutes after administration of the oxytocin bolus (T6), end of surgery (T7).

Requirements for additional vasoactive agents and any adverse effects and complications in the mother's health will also be recorded.

Hypotension will be defined as SAP < 80% of baseline, hypertension as SAP > 120% of baseline, and bradycardia as HR < 60 bpm. In case of hypotension combined with HR > 80/min, a dose of 50 μg of phenylephrine will be administered, while when hypotension is combined with HR < 80/min, a dose of 5 mg of ephedrine will be administered. Episodes of hypertension (SAP > 120% of baseline) will be treated by reducing the infusion of the "study drug" by half (15 ml/h) while if blood pressure rises to levels >130% of the baseline value, administration of the vasoconstrictor solution will be discontinued. In case of bradycardia (HR < 60 bpm) in combination with SAP within 80%-120% of baseline or hypertension, the infusion of the "study drug" will be discontinued without the administration of atropine. When HR < 55 bpm in combination with hypotension (SAP value < 80% of baseline) or in case of HR < 50 bpm regardless of the degree of hypotension, 0.6 mg of atropine will be administered.

Neonatal pH values in the first blood gas sample immediately after birth will be recorded, as well as the Apgar score at 1 and 5 minutes after birth.

The clinical interest of the study lies in determining whether the use of metaraminol is superior to the administration of norepinephrine as a vasoconstrictor during cesarean section and to what extent it ensures hemodynamic stability of the mother and a more favorable metabolic profile of the newborn.

Study Type

Interventional

Enrollment (Estimated)

80

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact Backup

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

adult parturients, singleton gestation, elective cesarean section

Exclusion Criteria:

ASA >II, age <18 years, Body Mass Index (BMI) >40 kg/m2, body weight <50 kg, body weight>100 kg, height<150 cm, height>180 cm, multiple gestation, fetal abnormality, fetal distress, active labor, emergency CT, cardiovascular disease or cerebrovascular disease, pre-existing or pregnancy-induced hypertension, use of antihypertensive medication during pregnancy, preeclampsia, any contraindication for regional anesthesia, such as thrombocytopenia or coagulation disorder, communication or language barriers, lack of informed consent

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Prevention
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Quadruple

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Active Comparator: Metaraminol group
Procedure: Metaraminol infusion
In parturients allocated to the metaraminol group, a metaraminol infusion (30 mL/h corresponding to 100 μg/min) will be initiated as soon as spinal anaesthesia is established.
Active Comparator: Norepinephrine group
Procedure: Norepinephrine infusion
In parturients allocated to the norepinephrine group, a norepinephrine infusion (30 mL/h corresponding to 4 μg/min) will be initiated as soon as spinal anaesthesia is established.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
incidence of hypotension
Time Frame: intraoperative
any occurrence of hypotension throughout the operation will be recorded (SAP < 80% of baseline)
intraoperative
number of hypotensive episodes in the pregnant woman
Time Frame: intraoperativre
the number of hypotensive episodes (SAP < 80% of baseline)throughout the operation will be recorded
intraoperativre
incidence of bradycardia
Time Frame: intraoperative
any incidence of HR < 60/min will be recorded
intraoperative

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
neonatal blood gases
Time Frame: 1 min post delivery
fetal cord blood analysis will be performed immediately post-delivery
1 min post delivery
glucose in neonatal blood
Time Frame: 1 min post delivery
glucose will be measured in the cord blood gas sample taken immediately post-delivery
1 min post delivery
need for vasoconstrictor
Time Frame: intraoperative
parturient needed or not vasoconstrictor during the operation
intraoperative
number of bolus doses of vasoconstrictor administered
Time Frame: intraoperative
number of provided interventions to maintain systolic blood pressure within the set limits will be recorded
intraoperative
total dose of vasoconstrictor administered
Time Frame: intraoperative
total dose in mg for ephedrine or μg for phenylephrine
intraoperative
incidence of hypertension
Time Frame: intraoperative
any incidence of systolic blood pressure >120% of baseline will be recorded
intraoperative
incidence of nausea/vomiting
Time Frame: intraoperative
incidence of nausea and vomiting throughout the operation
intraoperative
type of bolus vasopressor administered
Time Frame: intraoperative
phenylephrine verus ephedrine
intraoperative
need for administration of atropine
Time Frame: intraoperative
parturient needed or not atropine during the operation
intraoperative
need for differentiation in the basic infusion rate of the vasopressor solution
Time Frame: intraoperative
due to the occurrence of bradycardia or reactive hypertension
intraoperative
Incidence of dizziness, discomfort, and shivering
Time Frame: intraoperative
Incidence of dizziness, discomfort, and shivering through the operation
intraoperative
neonatal Apgar score
Time Frame: 1 min and 5 min post delivery
Neonatal Apgar score will be recorded at 1 min and at 5 min after delivery. The Apgar score is determined by evaluating the newborn baby on five simple criteria on a scale from zero to two, then summing up the five values thus obtained. The resulting Apgar score ranges from zero to 10. Scores 7 and above are generally normal; 4 to 6, fairly low; and 3 and below are generally regarded as critically low and cause for immediate resuscitative efforts.
1 min and 5 min post delivery

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Aretaieion University Hospital

Investigators

  • Study Director: Kassiani Theodoraki, Aretaieion University Hospital, National and Kapodistrian University of Athens

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Estimated)

February 1, 2026

Primary Completion (Estimated)

February 1, 2029

Study Completion (Estimated)

March 1, 2029

Study Registration Dates

First Submitted

January 15, 2026

First Submitted That Met QC Criteria

January 15, 2026

First Posted (Actual)

January 23, 2026

Study Record Updates

Last Update Posted (Actual)

January 23, 2026

Last Update Submitted That Met QC Criteria

January 15, 2026

Last Verified

January 1, 2026

More Information

Terms related to this study

Keywords

Other Study ID Numbers

  • 719/28-11-2025

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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