Oxytocin Bolus Versus Infusion in High-Risk Patients Undergoing Elective Cesarean Section (INBOX-HR) (INBOX-HR)

June 30, 2026 updated by: Tiffany E. Angelo, D.O., Stony Brook University

Randomized Double-Blinded Clinical Trial of Oxytocin Bolus Versus Infusion in High-Risk Patients Undergoing Elective Cesarean Section

The goal of this randomized, double-blind clinical trial is to learn if Oxytocin is most effective at achieving adequate uterine tone (important for preventing postpartum hemorrhage) when administered as a bolus or an infusion in patients at high-risk for postpartum hemorrhage in elective cesarean sections. The main questions that will be answered are:

  1. Is Oxytocin bolus more effective than Oxytocin infusion at achieving adequate uterine tone at 2 minutes after the baby is born and every minute thereafter?
  2. Does Oxytocin bolus cause less maternal side effects than Oxytocin infusion?
  3. Does Oxytocin bolus result in less blood loss than Oxytocin infusion in high risk for postpartum hemorrhage patients undergoing elective cesarean sections?

3. Are patients more satisfied with their cesarean section when they receive Oxytocin bolus or Oxytocin infusion?

Researchers will compare the 2 methods of Oxytocin administration, bolus versus infusion, to see which method is more effective or if they are equally effective.

Participants will:

  1. Be randomized to receive either Oxytocin bolus or Oxytocin infusion during their cesarean section but after the baby is born.
  2. Be asked a question about their experience 2 hours after the surgery.
  3. Allow the research team to collect information about how they are doing from their hospital medical records.

Study Overview

Status

Not yet recruiting

Conditions

Intervention / Treatment

Detailed Description

Oxytocin is the most commonly used uterotonic agent worldwide to achieve adequate uterine tone and prevent postpartum hemorrhage. Over the past decade, the trend has been towards lowering the dose to reduce oxytocin-related adverse effects including nausea, hypotension, chest pain, EKG changes, and maternal death. However, the optimal strategy for oxytocin administration remains controversial. A prior study was conducted at Stony Brook University Hospital which investigated the difference between bolus versus infusion administration of oxytocin in elective cesarean section patients with a low risk of postpartum hemorrhage (PPH); the results of this randomized, double blinded clinical trial showed that bolus was not superior for adequate uterine tone at 2 minutes when compared to infusion of oxytocin, but blood loss was modestly lower and total oxytocin exposure was substantially lower in the bolus arm. Which makes the most logical next question: Does bolus oxytocin become more clinically meaningful in patients with higher baseline risk for uterine atony or hemorrhage. The investigators aim to address this question with the INBOX-HR study.

INBOX-HR acts as a continuing investigation on the difference between bolus versus infusion administration of oxytocin, specifically for patients that are at a high risk for postpartum hemorrhage. Thus, the purpose of this research study is to compare bolus and infusion administration of oxytocin on parturients at high risk for postpartum hemorrhage undergoing elective cesarean section. The primary objective of this study is to test the hypothesis that administration by bolus vs. infusion results in more rapid achievement of adequate uterine tone in this patient population. Secondary objectives include determining estimated blood loss, prevalence of hypotension, change in heart rate, nausea, vomiting, and patient satisfaction, and 0 - 10 uterine tone score.

Study Type

Interventional

Enrollment (Estimated)

180

Phase

  • Phase 4

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:

  • Undergoing elective cesarean section under spinal anesthesia or combined spinal anesthesia (CSE)
  • Patients must be able to provide written informed consent in either English or Spanish
  • Parturient classified as high risk for postpartum hemorrhage as defined by the adapted California Maternal Quality Care Obstetric Hemorrhage Risk Screen

Exclusion Criteria:

  • Parturient in labor or ruptured membranes
  • Patient does not possess the physical and mental capacity to provide informed consent
  • Urgent or emergent cesarean sections
  • Patients with a known major coagulopathy
  • Patients with significant thrombocytopenia limiting neuraxial anesthesia (<70k)
  • Patients on therapeutic anticoagulation at time of procedure
  • Patients on the placenta accreta spectrum
  • Patients with severe cardiac disease contraindicating oxytocin
  • Patients with an allergy to oxytocin

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: Other
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Triple

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Active Comparator: Oxytocin Bolus
Patients in the bolus arm will receive a 3 IU oxytocin IV bolus over 15 seconds after delivery of the baby/uterine cord clamping and a maintenance infusion of 0.9% Saline will be started at 225ml/hr. If uterine tone is considered inadequate after an additional 3 minutes, a second bolus of 3 IU oxytocin is given IV over 15 seconds. If uterine tone is inadequate after an additional 3 minutes, a third bolus of 3 IU Oxytocin IV is given over 15 seconds. If after an additional 3 mins uterine tone is still inadequate, a second infusion consisting of oxytocin 3 IU/hr is started at 100ml/hrs and continued for a total of 4 hours, second line uterotonic agents (Methergine, Hemabate and/ or Cytotec) will be given, and the maintenance 0.9% Saline infusion will be changed to 450 ml/hr for a total of 1 hour, then changed to 38 ml/ hour for the following 3 hours. If uterine tone is considered adequate at 3, 6 or 9 minutes, a second infusion of oxytocin 3 IU/hr (100ml/hr) is started and maintained
Drug: Oxytocin Bolus or Oxytocin Infusion

On the day of surgery, patients will be randomized to receive either bolus or infusion administration of Oxytocin.

On the day of the procedure, periprocedural data and patient satisfaction (single question) will be recorded.
Active Comparator: Oxytocin Infusion
Patients in the infusion arm will receive a bolus of IV 0.9% Saline over 15 seconds after delivery of the baby/uterine cord clamping and a maintenance infusion of 18 IU/hr Oxytocin IV (225ml/hr). If uterine tone is considered inadequate after an additional 3 minutes, a second bolus of 0.9% Saline will be given IV over 15 seconds. If uterine tone is inadequate after an additional 3 minutes, a third bolus of 0.9% Saline will be given IV over 15 seconds. If after an additional 3 mins uterine tone is still inadequate, a second infusion of 0.9% Saline will be started at 100 ml/hr for 4 hours, second line uterotonic agents (Methergine, Hemabate and/or Cytotec) will be given, and the Oxytocin infusion will be changed to 36 IU/hour (450 ml/hr) for a total of 1 hour, and then changed to 38 ml/hr for the following 3 hours. If uterine tone is considered adequate at 3, 6 or 9 minutes, a second infusion of 0.9% Saline at 100 ml/hr will be started and maintained for 4 hours.
Drug: Oxytocin Bolus or Oxytocin Infusion

On the day of surgery, patients will be randomized to receive either bolus or infusion administration of Oxytocin.

On the day of the procedure, periprocedural data and patient satisfaction (single question) will be recorded.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Time to uterine tone
Time Frame: 2 minutes after umbilical cord clamp until 10 minutes.
Uterine tone will be assessed at 2 mins and then every minute thereafter until adequate uterine tone is attained but no more than 10 minutes maximum, by a blinded obstetrician. Uterine tone will be deemed adequate or inadequate by the blinded obstetrician. The time for the primary endpoint analysis is adequacy of uterine tone at 2 minutes after the baby is born/umbilical cord clamped.
2 minutes after umbilical cord clamp until 10 minutes.

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Estimated intraoperative blood loss
Time Frame: From the start to end of surgery
From the start to end of surgery
Changes in heart rate (beats per minute)
Time Frame: During uterine cord clamp and every 2 minutes thereafter until 10 minutes
During uterine cord clamp and every 2 minutes thereafter until 10 minutes
Changes in blood pressure (mmHg)
Time Frame: During uterine cord clamp and every 2 minutes thereafter until 10 minutes.
During uterine cord clamp and every 2 minutes thereafter until 10 minutes.
Total dose of phenylephrine administered intraoperatively
Time Frame: From the start to end of surgery
From the start to end of surgery
Need for additional uterotonic agents
Time Frame: From oxytocin administration until end of surgery
Such as Methergine, Hemabate, and Cytotec
From oxytocin administration until end of surgery
0-10 Uterine tone score
Time Frame: 2 minutes after uterine cord clamping until 10 minutes.
Uterine tone score will be assessed at 2 mins and then every minute thereafter.
2 minutes after uterine cord clamping until 10 minutes.
Maternal side effects
Time Frame: From oxytocin administration until end of surgery
Chest pain, nausea, vomiting
From oxytocin administration until end of surgery
Patient satisfaction questionnaire
Time Frame: 2 hours after surgery
The patient will be asked a question about their experience on a scale of 0-10 (0 being complete dissatisfaction, and 10 being highly satisfied).
2 hours after surgery

Collaborators and Investigators

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

Sponsor

Stony Brook University

Investigators

  • Principal Investigator: Tiffany E Angelo, DO, FASA, Stony Brook University Hospital Department of Anesthesiology

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)

August 1, 2026

Primary Completion (Estimated)

August 1, 2028

Study Completion (Estimated)

February 1, 2029

Study Registration Dates

First Submitted

June 24, 2026

First Submitted That Met QC Criteria

June 30, 2026

First Posted (Actual)

July 7, 2026

Study Record Updates

Last Update Posted (Actual)

July 7, 2026

Last Update Submitted That Met QC Criteria

June 30, 2026

Last Verified

June 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • IRB2026-00322

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

UNDECIDED

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

Yes

Studies a U.S. FDA-regulated device product

No

product manufactured in and exported from the U.S.

Yes

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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