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

Not Applicable

Recruiting

• Conditions: Postpartum Hemorrhage
• Interventions: Drug: Oxytocin

• Registration Number: NCT05290129
• Lead Sponsor: Samuel Lunenfeld Research Institute, Mount Sinai Hospital

Brief Summary

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.

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 Timeline

• Study First Submitted: 2022-03-11
• Study First Submitted QC: 2022-03-11
• Study First Posted: 2022-03-22
• Study Start: 2022-08-17
• Status Verified: 2025-05
• Last Update Submitted: 2025-05-21
• Last Update Posted: 2025-05-25
• Primary Completion: 2025-07
• Study Completion: 2025-07

Recruitment & Eligibility

• Status: RECRUITING
• Sex: Female
• Target Recruitment: 40

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 & Design

• Study Type: INTERVENTIONAL
• Study Design: PARALLEL

Arm && Interventions

Group	Intervention	Description
Oxytocin infusion rate 4 IU/h	Oxytocin	The maintenance infusion rate of oxytocin will be 4 IU/h.
Oxytocin infusion rate 6 IU/h	Oxytocin	The maintenance infusion rate of oxytocin will be 6 IU/h.
Oxytocin infusion rate 10 IU/h	Oxytocin	The maintenance infusion rate of oxytocin will be 10 IU/h.
Oxytocin infusion rate 14 IU/h	Oxytocin	The maintenance infusion rate of oxytocin will be 14 IU/h.
Oxytocin infusion rate 18 IU/h	Oxytocin	The maintenance infusion rate of oxytocin will be 18 IU/h.
Oxytocin infusion rate 26 IU/h	Oxytocin	The maintenance infusion rate of oxytocin will be 26 IU/h.
Oxytocin infusion rate 22 IU/h	Oxytocin	The maintenance infusion rate of oxytocin will be 22 IU/h.
Oxytocin infusion rate 30 IU/h	Oxytocin	The maintenance infusion rate of oxytocin will be 30 IU/h.
Oxytocin infusion rate 34 IU/h	Oxytocin	The maintenance infusion rate of oxytocin will be 34 IU/h.
Oxytocin infusion rate 36 IU/h	Oxytocin	The maintenance infusion rate of oxytocin will be 36 IU/h.

Primary Outcome Measures

Name	Time	Method
Uterine tone up to discharge from the post anesthetic care unit (PACU): questionnaire	2 hours	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.

Secondary Outcome Measures

Name	Time	Method
Presence of atrial fibrillation: ECG	2 hours	Presence of atrial fibrillation as recorded by ECG, from drug administration until end of surgery
Hypotension: systolic blood pressure less than 80% of baseline	2 hours	Systolic blood pressure \< 80% of baseline, from drug administration until end of surgery
Presence of chest pain: questionnaire	2 hours	Any presence of chest pain, from drug administration until end of surgery, as reported by the patient
Requirement for additional uterotonic medication from discharge from the PACU until 24 hours postpartum.	24 hours	Any uterotonic medication administered after the patient is discharged from PACU until 24 hours postpartum.
Tachycardia: heart rate greater than 130% of baseline	2 hours	Heart rate \> 130% of baseline, from drug administration until end of surgery
Presence of ventricular tachycardia: ECG	2 hours	Presence of ventricular tachycardia as recorded by ECG, from drug administration until end of surgery
Need for blood transfusion	24 hours	Blood product administered.
Requirement for additional uterotonic medication in the PACU	2 hours	Any uterotonic medication administered while the patient is in PACU
Bradycardia: heart rate less than 70% of baseline	2 hours	Heart rate \< 70% of baseline or a heart rate \< 50bpm, from drug administration until end of surgery
Presence of nausea: questionnaire	2 hours	The presence of nausea and number of episodes, from drug administration until end of surgery, as reported by the patient
Presence of vomiting: questionnaire	2 hours	The presence of vomiting and number of episodes, from drug administration until end of surgery
Presence of shortness of breath: questionnaire	2 hours	Any presence of shortness of breath, from drug administration until end of surgery, as reported by the patient
Presence of headache: questionnaire	2 hours	Any presence of headache, from drug administration until end of surgery, as reported by the patient
Calculated blood loss	24 hours	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.
Episodes of bleeding postpartum	24 hours	Number of episodes of bleeding postpartum up to 24 hours post delivery.
Intraoperative requirement for additional uterotonic medication	1 hour	A request made by the obstetrician performing the cesarean delivery for additional uterotonic medication, due to bleeding or poor uterine tone.
Hypertension: systolic blood pressure greater than 120% of baseline	2 hours	Systolic blood pressure \> 120% of baseline, from drug administration until end of surgery
Presence of atrial flutter: ECG	2 hours	Presence of atrial flutter as recorded by ECG, from drug administration until end of surgery

Trial Locations

Locations (1)

Mount Sinai Hospital; 🇨🇦 Toronto, Ontario, Canada