Changes in Velocimetric Indices of Uterine and Umbilical Arteries Before and After Combined Spinal-epidural Analgesia in Laboring Women

Combined spinal-epidural (CSE) for labor analgesia has been used for many years and is practiced commonly at our institution, especially when the patient requests immediate pain relief. CSE is not only beneficial for its faster onset of analgesia, but also it is favorable in relation to the need for rescue analgesia, urinary retention, and rate of instrumental delivery compared to the traditional epidural. Despite its beneficial effects, there is a risk of about 15-30% of developing abnormal fetal heart rate following CSE. This is self-resolving with minimal or no intervention. Although the cause of fetal bradycardia is not fully elucidated, variations in uterine artery blood flow after epidural analgesia are thought to be due to the interaction of numerous events related to blockade of sympathetic innervations, fluid administration, maternal hypotension, uterine vascular effects of sympathetic block, fluctuations in circulating catecholamines, and possibly the effect of opioids. Similar mechanism is thought to be a cause of fetal bradycardia after the CSE with its faster onset and superior block.

Maternal or fetal circulation during labor can be assessed using continuous-wave Doppler ultrasound to monitor maternal uterine artery (UtA) and fetal umbilical artery (UmA) velocity waveforms to detect changes in blood flow. The velocimetry indices mentioned above have been often used to assess the changes in the blood flow before and after the induction of epidural analgesia during labor in several studies. Although there are some studies regarding the effect of labor epidural analgesia using velocimetry indices, but there is currently no published study evaluating velocimetry indices of uterine and umbilical arteries before and after the induction of CSE. Thus, the aim of this study is to investigate the impact of CSE to maternal and fetal blood flow to evaluate the relationships.

The investigators hypothesize that both uterine artery and umbilical artery blood flow are reduced after the induction of CSE, which may be responsible for the occurrence of fetal bradycardia.

Study Overview

• Status: Completed
• Conditions: Labor Pain
• Intervention / Treatment: Device: Ultrasound

• Study Type: Interventional
• Enrollment (Actual): 30
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Canada
  • Ontario
    • Toronto, Ontario, Canada, M5G1X5
      • Mount Sinai Hospital

Participation Criteria

Eligibility Criteria

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

Description

Inclusion Criteria:

• Written informed consent
• Term pregnant patients requesting labor analgesia
• Singleton pregnancy
• Term pregnant patients in active labor
• ASA<4
• No evidence of fetal congenital anomalies, fetal compromise or fetal decelerations prior to CSE

Exclusion Criteria:

• Refusal to consent for the study
• Known spinal deformities
• Previous back instrumentation
• Patients with BMI>50 kg/㎡ due to anticipated technical challenges in Doppler studies

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Diagnostic
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Ultrasound; Ultrasound will be used to measure velocimetric indices of both right and left uterine arteries and umbilical artery.	Device: Ultrasound; Ultrasound scan of the right and left uterine arteries and umbilical artery.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Uterine artery velocimetric index - systolic/diastolic ratio (S/D) at baseline	Uterine artery velocimetric index - systolic/diastolic ratio (S/D) will be measured at baseline (prior to combined spinal epidural).	5 minutes
Uterine artery velocimetric index - systolic/diastolic ratio (S/D) at 10 minutes	Uterine artery velocimetric index - systolic/diastolic ratio (S/D) will be measured 10 minutes after combined spinal epidural	5 minutes
Uterine artery velocimetric index - systolic/diastolic ratio (S/D) at 30 minutes	Uterine artery velocimetric index - systolic/diastolic ratio (S/D) will be measured 30 minutes after combined spinal epidural	5 minutes
Uterine artery velocimetric index - pulsatility index (PI) at baseline	Uterine artery velocimetric index - pulsatility index (PI) will be measured at baseline (prior to combined spinal epidural).	5 minutes
Uterine artery velocimetric index - pulsatility index (PI) at 10 minutes	Uterine artery velocimetric index - pulsatility index (PI) will be measured 10 minutes after combined spinal epidural	5 minutes
Uterine artery velocimetric index - pulsatility index (PI) at 30 minutes	Uterine artery velocimetric index - pulsatility index (PI) will be measured 30 minutes after combined spinal epidural	5 minutes
Uterine artery velocimetric index - resistance index (RI) at baseline	Uterine artery velocimetric index - resistance index (PI) will be measured at baseline (prior to combined spinal epidural).	5 minutes
Uterine artery velocimetric index - resistance index (RI) at 10 minutes	Uterine artery velocimetric index - resistance index (PI) will be measured 10 minutes after combined spinal epidural	5 minutes
Uterine artery velocimetric index - resistance index (RI) at 30 minutes	Uterine artery velocimetric index - resistance index (PI) will be measured 30 minutes after combined spinal epidural	5 minutes
Umbilical artery velocimetric index - systolic/diastolic ratio (S/D) at baseline	Umbilical artery velocimetric index - systolic/diastolic ratio (S/D) will be measured at baseline (prior to combined spinal epidural).	5 minutes
Umbilical artery velocimetric index - systolic/diastolic ratio (S/D) at 10 minutes	Umbilical artery velocimetric index - systolic/diastolic ratio (S/D) will be measured 10 minutes after combined spinal epidural	5 minutes
Umbilical artery velocimetric index - systolic/diastolic ratio (S/D) at 30 minutes	Umbilical artery velocimetric index - systolic/diastolic ratio (S/D) will be measured 30 minutes after combined spinal epidural	5 minutes
Umbilical artery velocimetric index - pulsatility index (PI) at baseline	Umbilical artery velocimetric index - pulsatility index (PI) will be measured at baseline (prior to combined spinal epidural).	5 minutes
Umbilical artery velocimetric index - pulsatility index (PI) at 10 minutes	Umbilical artery velocimetric index - pulsatility index (PI) will be measured 10 minutes after combined spinal epidural	5 minutes
Umbilical artery velocimetric index - pulsatility index (PI) at 30 minutes	Umbilical artery velocimetric index - pulsatility index (PI) will be measured 30 minutes after combined spinal epidural	5 minutes
Umbilical artery velocimetric index - resistance index (PI) at baseline	Umbilical artery velocimetric index - resistance index (PI) will be measured at baseline (prior to combined spinal epidural).	5 minutes
Umbilical artery velocimetric index - resistance index (PI) at 10 minutes	Umbilical artery velocimetric index - resistance index (PI) will be measured 10 minutes after combined spinal epidural	5 minutes
Umbilical artery velocimetric index - resistance index (PI) at 30 minutes	Umbilical artery velocimetric index - resistance index (PI) will be measured 30 minutes after combined spinal epidural	5 minutes

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Pain score at baseline - questionnaire	Pain score - verbal numeric rating scale (0-10) prior to combined spinal epidural	1 minute
Pain score at 10 min - questionnaire	Pain score - verbal numeric rating scale (0-10) at 10 min after combined spinal epidural	1 minute
Pain score at 30 min - questionnaire	Pain score - verbal numeric rating scale (0-10) at 30 min after combined spinal epidural	1 minute
Hypotension: systolic blood pressure less than 80% of baseline	Systolic blood pressure < 80% of baseline, monitored q5 for 30 minutes following combined spinal epidural	30 minutes
Hypertension: systolic blood pressure greater than 120% of baseline	Systolic blood pressure > 120% of baseline, monitored q5 for 30 minutes following combined spinal epidural	30 minutes
Bradycardia: heart rate less than 70% of baseline	Heart rate < 70% of baseline or a heart rate < 50bpm, monitored q5 for 30 minutes following combined spinal epidural	30 minutes
Desaturation: oxygen level <95%	Oxygen level <95%, monitored q5 for 30 minutes following combined spinal epidural	30 minutes
Sensory block level at 10 minutes	Sensory block level at 10 minutes following combined spinal epidural	10 minutes
Sensory block level at 30 minutes	Sensory block level at 30 minutes following combined spinal epidural	30 minutes
Duration of labour	Onset of labour until delivery of the placenta	up to 24 hours
Type of delivery	Type of delivery will be recorded: vaginal, cesarean section, instrumental delivery	up to 24 hours
Presence of hypertonic uterine contractions	Presence of hypertonic uterine contractions as noted by the nursing or obstetric team.	up to 24 hours
fetal heart rate at baseline	fetal heart rate at baseline, prior to combined spinal epidural	5 minutes
fetal heart rate q5 min up to 30 minutes	fetal heart rate q5 min up to 30 minutes following combined spinal epidural	30 minutes
presence of fetal bradycardia - questionnaire	presence of fetal bradycardia (fetal heart rate <110)	up to 24 hours
presence of fetal tachycardia - questionnaire	presence of fetal tachycardia (fetal heart rate >160)	up to 24 hours
Neonatal weight	Neonatal weight measured after delivery in grams	2 minutes
Apgar score at 1 minute	Apgar score at 1 minute	1 minute
Apgar score at 5 minutes	Apgar score at 5 minutes	5 minute2

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): September 14, 2022
• Primary Completion (Actual): March 30, 2024
• Study Completion (Actual): March 30, 2024

Study Registration Dates

• First Submitted: August 19, 2022
• First Submitted That Met QC Criteria: August 19, 2022
• First Posted (Actual): August 23, 2022

Study Record Updates

• Last Update Posted (Actual): October 24, 2024
• Last Update Submitted That Met QC Criteria: October 22, 2024
• Last Verified: October 1, 2023

More Information

Terms related to this study

• Keywords: ultrasound; fetal bradycardia; combined spinal epidural (CSE); velocimetric index
• Additional Relevant MeSH Terms: Pain; Neurologic Manifestations; Labor Pain
• Other Study ID Numbers: 22-04

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