Oxytocin Maintenance Infusion in Labouring Women Undergoing Cesarean Delivery: an Up-down Sequential Allocation Study

This study is designed to determine the minimal effective oxytocin maintenance infusion required in labouring women undergoing cesarean delivery to achieve the best effect. Oxytocin is a drug that is routinely used to help the uterus to contract and keep it contracted after delivery. Consequently, it will help to reduce blood loss after delivery. In order to determine the minimal effective dose, the investigators will conduct a dose-finding study. The first patient will receive a set oxytocin infusion. The next patient's infusion dose of oxytocin, will either increase or decrease, depending on how the previous patient responds in terms of uterine tone. If the response is satisfactory with the infusion dose used, the next patient will either receive the same infusion dose or it will be decreased depending on a probability of 1:9. If the response is not satisfactory, then the infusion dose will increase for the next patient. The dose for each patient will be determined based on the results of the uterine contraction of the previous patient.

The investigators hypothesize that the ED90 of the oxytocin infusion rate to maintain adequate uterine tone in labouring women with induced or augmented labour undergoing cesarean delivery, following an initial effective bolus dose, would be lower than 0.74 IU/min (44 IU/h), which was found as the ED90 in a previous study, without an initial bolus dose prior to the infusion.

Study Overview

• Status: Recruiting
• Conditions: Postpartum Hemorrhage
• Intervention / Treatment: Drug: Oxytocin

Detailed Description

This study will be conducted as a prospective, double blinded clinical trial (patient, anesthesiologist and obstetrician blinded to the oxytocin dose), in an up-down sequential allocation fashion. The objective of the study is to determine the minimum effective dose of oxytocin infusion required to produce appropriate uterine contraction during and after cesarean delivery under neuraxial anesthesia in laboring women. For the purpose of this study, the minimum effective dose is defined to be that at which adequate response occurs in 90% of patients, i.e. ED90.

• Study Type: Interventional
• Enrollment (Estimated): 40
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Mrinalini Balki, MD; Phone Number: 5270 416-586-4800; Email: mrinalini.balki@uhn.ca

Study Locations

• Canada
  • Ontario
    • Toronto, Ontario, Canada, M5G1X5
      • Recruiting
      • Mount Sinai Hospital
      • Sub-Investigator: Jose Carvalho, MD
      • Sub-Investigator: Genevieve Lachance, MD
      • Sub-Investigator: Jackie Thomas, MD
      • Sub-Investigator: Atsuko Hirano, MD
      • Sub-Investigator: Kristi Downey, MSc
      • Sub-Investigator: Xiang Y Ye, MSc
      • Contact: Mrinalini Balki, MD; Phone Number: 5270 416-586-4800; Email: mrinalini.balki@uhn.ca

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 50 years (Adult)
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• All patients with induced or augmented labour undergoing cesarean delivery under neuraxial anesthesia (at least 3 hours of prior exposure to oxytocin during labour)

Exclusion Criteria:

• All patients who refuse to give written informed consent
• All patients who declare allergy or hypersensitivity to oxytocin
• A history of hypertension and/or severe cardiac disease(s)
• All patients who have contraindications for neuraxial anesthesia
• All patients who will be converted to general anesthesia intraoperatively
• All patients with placenta previa and multiple gestation

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Non-Randomized
• Interventional Model: Parallel Assignment
• Masking: Quadruple

Number of Arms

10

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Oxytocin infusion rate 4 IU/h; The maintenance infusion rate of oxytocin will be 4 IU/h.	Drug: Oxytocin; Oxytocin will be prepared in a 1L bag of Ringer's lactate, to be infused at a rate of 125 ml/h.; Other Names: Pitocin
Experimental: Oxytocin infusion rate 6 IU/h; The maintenance infusion rate of oxytocin will be 6 IU/h.	Drug: Oxytocin; Oxytocin will be prepared in a 1L bag of Ringer's lactate, to be infused at a rate of 125 ml/h.; Other Names: Pitocin
Experimental: Oxytocin infusion rate 10 IU/h; The maintenance infusion rate of oxytocin will be 10 IU/h.	Drug: Oxytocin; Oxytocin will be prepared in a 1L bag of Ringer's lactate, to be infused at a rate of 125 ml/h.; Other Names: Pitocin
Experimental: Oxytocin infusion rate 14 IU/h; The maintenance infusion rate of oxytocin will be 14 IU/h.	Drug: Oxytocin; Oxytocin will be prepared in a 1L bag of Ringer's lactate, to be infused at a rate of 125 ml/h.; Other Names: Pitocin
Experimental: Oxytocin infusion rate 18 IU/h; The maintenance infusion rate of oxytocin will be 18 IU/h.	Drug: Oxytocin; Oxytocin will be prepared in a 1L bag of Ringer's lactate, to be infused at a rate of 125 ml/h.; Other Names: Pitocin
Experimental: Oxytocin infusion rate 22 IU/h; The maintenance infusion rate of oxytocin will be 22 IU/h.	Drug: Oxytocin; Oxytocin will be prepared in a 1L bag of Ringer's lactate, to be infused at a rate of 125 ml/h.; Other Names: Pitocin
Experimental: Oxytocin infusion rate 26 IU/h; The maintenance infusion rate of oxytocin will be 26 IU/h.	Drug: Oxytocin; Oxytocin will be prepared in a 1L bag of Ringer's lactate, to be infused at a rate of 125 ml/h.; Other Names: Pitocin
Experimental: Oxytocin infusion rate 30 IU/h; The maintenance infusion rate of oxytocin will be 30 IU/h.	Drug: Oxytocin; Oxytocin will be prepared in a 1L bag of Ringer's lactate, to be infused at a rate of 125 ml/h.; Other Names: Pitocin
Experimental: Oxytocin infusion rate 34 IU/h; The maintenance infusion rate of oxytocin will be 34 IU/h.	Drug: Oxytocin; Oxytocin will be prepared in a 1L bag of Ringer's lactate, to be infused at a rate of 125 ml/h.; Other Names: Pitocin
Experimental: Oxytocin infusion rate 36 IU/h; The maintenance infusion rate of oxytocin will be 36 IU/h.	Drug: Oxytocin; Oxytocin will be prepared in a 1L bag of Ringer's lactate, to be infused at a rate of 125 ml/h.; Other Names: Pitocin

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Uterine tone up to discharge from the post anesthetic care unit (PACU): questionnaire	Uterine tone will be evaluated as satisfactory or unsatisfactory by the obstetrician throughout the surgery, starting at 5 minutes after the oxytocin infusion. It will also be measured at 10 minutes following the oxytocin infusion and every 10 minutes following that for the duration of the surgery. Unsatisfactory uterine tone at any time until discharge from the PACU will be considered a failure of the maintenance infusion.	2 hours

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Calculated blood loss	Estimated blood loss will be calculated using the difference in hematocrit values prior to surgery and 24 hours post surgery, using the following formula: Calculated blood loss (mL) = EBV ((Pre-op Htc-Post-op Htc)/pre-op Htc) EBV (estimated blood volume) in ml: patient's weight in kg x 85.	24 hours
Need for blood transfusion	Blood product administered.	24 hours
Episodes of bleeding postpartum	Number of episodes of bleeding postpartum up to 24 hours post delivery.	24 hours
Requirement for additional uterotonic medication in the PACU	Any uterotonic medication administered while the patient is in PACU	2 hours
Requirement for additional uterotonic medication from discharge from the PACU until 24 hours postpartum.	Any uterotonic medication administered after the patient is discharged from PACU until 24 hours postpartum.	24 hours
Hypotension: systolic blood pressure less than 80% of baseline	Systolic blood pressure < 80% of baseline, from drug administration until end of surgery	2 hours
Hypertension: systolic blood pressure greater than 120% of baseline	Systolic blood pressure > 120% of baseline, from drug administration until end of surgery	2 hours
Tachycardia: heart rate greater than 130% of baseline	Heart rate > 130% of baseline, from drug administration until end of surgery	2 hours
Bradycardia: heart rate less than 70% of baseline	Heart rate < 70% of baseline or a heart rate < 50bpm, from drug administration until end of surgery	2 hours
Presence of ventricular tachycardia: ECG	Presence of ventricular tachycardia as recorded by ECG, from drug administration until end of surgery	2 hours
Presence of atrial fibrillation: ECG	Presence of atrial fibrillation as recorded by ECG, from drug administration until end of surgery	2 hours
Presence of atrial flutter: ECG	Presence of atrial flutter as recorded by ECG, from drug administration until end of surgery	2 hours
Presence of nausea: questionnaire	The presence of nausea and number of episodes, from drug administration until end of surgery, as reported by the patient	2 hours
Presence of vomiting: questionnaire	The presence of vomiting and number of episodes, from drug administration until end of surgery	2 hours
Presence of chest pain: questionnaire	Any presence of chest pain, from drug administration until end of surgery, as reported by the patient	2 hours
Presence of shortness of breath: questionnaire	Any presence of shortness of breath, from drug administration until end of surgery, as reported by the patient	2 hours
Presence of headache: questionnaire	Any presence of headache, from drug administration until end of surgery, as reported by the patient	2 hours
Intraoperative requirement for additional uterotonic medication	A request made by the obstetrician performing the cesarean delivery for additional uterotonic medication, due to bleeding or poor uterine tone.	1 hour

Collaborators and Investigators

• Sponsor: Samuel Lunenfeld Research Institute, Mount Sinai Hospital
• Investigators: Principal Investigator: Mrinalini Balki, MD, Mount Sinai Hospital

Study record dates

Study Major Dates

• Study Start (Actual): August 17, 2022
• Primary Completion (Estimated): December 1, 2026
• Study Completion (Estimated): December 1, 2026

Study Registration Dates

• First Submitted: March 11, 2022
• First Submitted That Met QC Criteria: March 11, 2022
• First Posted (Actual): March 22, 2022

Study Record Updates

• Last Update Posted (Actual): April 6, 2026
• Last Update Submitted That Met QC Criteria: March 31, 2026
• Last Verified: February 1, 2026

More Information

Terms related to this study

• Keywords: oxytocin; pregnancy; Cesarean delivery; labour; uterotonic
• Additional Relevant MeSH Terms: Urogenital Diseases; Pathologic Processes; Female Urogenital Diseases and Pregnancy Complications; Obstetric Labor Complications; Pregnancy Complications; Hemorrhage; Puerperal Disorders; Uterine Hemorrhage; Pathological Conditions, Signs and Symptoms; Postpartum Hemorrhage; Hormones; Hormones, Hormone Substitutes, and Hormone Antagonists; Peptide Hormones; Peptides; Amino Acids, Peptides, and Proteins; Pituitary Hormones, Posterior; Pituitary Hormones; Oxytocin
• Other Study ID Numbers: 22-02

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
• product manufactured in and exported from the U.S.: No