Femoral Vein Collapsibility Index and Post-Spinal Hypotension in Pregnant Women: Impact of Position

"Can Femoral Vena Cava Collapsibility Index Predict Post-spinal Hypotension in Pregnant Women in Left Lateral Tilt Position?"

This study aims to improve the safety of spinal anesthesia for pregnant patients undergoing elective cesarean delivery. Specifically, the investigators are investigating whether ultrasound measurements of a vein in the groin (the right common femoral vein, or RCFV) can help predict the risk of low blood pressure (hypotension) after spinal anesthesia. The main question it aims to answer is:

Can femoral vena cava collapsibility index predict post-spinal hypotension in pregnant women in left lateral tilt position?

Before receiving spinal anesthesia, participants will undergo a brief and painless ultrasound examination of the RCFV in the groin area while lying in a specific position."

Study Overview

• Status: Not yet recruiting
• Conditions: Spinal Induced Hypotension in Cesarean Delivery
• Intervention / Treatment: Diagnostic test: Supine Position; Diagnostic test: Supine Position; Diagnostic test: Left Lateral Tilt Position

Detailed Description

Post-spinal hypotension (PSH) is defined as a systolic arterial blood pressure (SBP) decrease of more than 20% from baseline or an SBP drop below 100 mmHg. This reduction in blood pressure may compromise uteroplacental perfusion, leading to fetal hypoxia and acidosis. PSH is the most common complication in obstetric anesthesia, with an incidence of up to 95% in healthy women. Despite extensive research, the most effective strategy to maintain hemodynamic stability remains under investigation. Various methods, including crystalloid and colloid fluid loading, leg wrapping, head-down tilt, and vasopressor use, have been explored for both treatment and prevention.

The sympatholytic effect of spinal anesthesia induces vasodilation, exacerbating maternal hypotension due to the gravid uterus compressing the inferior vena cava (IVC). This compression reduces venous return and subsequently decreases the IVC diameter.

Current recommendations for term pregnant women undergoing cesarean delivery advocate for a left lateral tilt position to prevent aortocaval compression (ACC), maternal hypotension, and fetal compromise . In the supine position, the IVC is nearly completely obstructed at term up to its bifurcation. However, most women experience only minimal hemodynamic effects due to compensatory mechanisms such as venoconstriction in the lower extremities and collateral circulation via the paraspinal and azygos veins. Clinically significant hemodynamic compromise, known as supine hypotensive syndrome, occurs in approximately 8-10% of term pregnancies, likely due to insufficient compensatory responses .

The right common femoral vein (RCFV), a continuation of the right external iliac vein, is a tributary of the IVC. Because the RCFV is superficially located, it can be easily visualized using a high-frequency ultrasound probe. Importantly, the RCFV is situated distal to the site of aortocaval compression, making it a potential surrogate marker for hemodynamic changes.

Study Hypothesis This study hypothesizes that the peak velocity and collapsibility index of the RCFV in the inguinal region, measured in the left lateral 15-degree tilt position, reflect the degree of aortocaval compression. These parameters may help identify pregnant women at high risk of post-spinal hypotension during elective cesarean delivery.

• Study Type: Interventional
• Enrollment (Estimated): 100
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: MEHMET SARI Dr, Medical Doctor; Phone Number: +095454624611; Email: mehmet.sari@bezmialem.edu.tr

Study Locations

• Turkey
  • Istanbul, Turkey, 34844
    • Bezmialem Vakıf Univeristesi Dragos Hastanesi Yalı, Kennedy Cd. No:16.
    • Contact: Kazım Karaaslan Head of Department, Medical Doctor, Professor; Phone Number: +905055213865; Email: kkaraaslan@bezmialem.edu.tr
    • Contact: Mehmet SARI, Medical Doctor

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• ASA 2
• Uncomplicated pregnancy
• Height between 150 cm-180 cm
• Signed the informed consent form
• 8 hours of fasting before the operation
• Patients who refuse normal delivery

Exclusion Criteria:

• Obstetric comorbidities affecting caval compression of the aorta
• Transverse development
• Fetal macrosomia
• Uterine anomaly
• Polyhydramnion
• Oligohydroamnion
• Membrane ruptures
• Intrauterine growth retardation
• Mothers with hyperactive lung disease
• Those with autonomic neuropathy
• Kidney failure
• Smokers
• Severe scoliosis or kyphosis
• Multiple pregnancy (twins, triplets,...)
• Those who do not reach T6 sensory block level after 10 minutes
• Those undergoing general anesthesia or IV analgesics for any reason

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: Non-Randomized
• Interventional Model: Crossover Assignment
• Masking: Quadruple

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Sham Comparator: Supine Position; All ultrasonography (USG) procedures will be performed by the same anesthesiologist using a Ultrasound device before the start of spinal anesthesia (SA) and after baseline blood pressure and heart rate have been measured. Patients will be placed in supine position. After at least 3 minutes in each position, ultrasound of the inferior vena cava (IVC) and femoral vein (FV) will be performed. The oblique probe will be placed below the xiphoid. Anteroposterior diameters and peak velocities of the IVC will be measured 2-3 cm below the IVC-right atrium For standardization purposes, measurements of the right femoral vein will be used in the study. The FV will be visualized with B-mode ultrasound 2-5 cm below the level of the inguinal ligament where the femoral artery is best palpated, without applying any pressure that may affect the FV diameter.	Diagnostic test: Supine Position; All ultrasonography (USG) procedures will be performed by the same anesthesiologist using a Ultrasound device before the start of spinal anesthesia (SA) and after baseline blood pressure and heart rate have been measured. Patients will be placed in supine and left lateral tilt (LLT) positions. After at least 3 minutes in each position, ultrasound of the inferior vena cava (IVC) and femoral vein (FV) will be performed. The oblique probe will be placed below the xiphoid. Anteroposterior diameters and peak velocities of the IVC will be measured 2-3 cm below the IVC-right atrium For standardization purposes, measurements of the right femoral vein will be used in the study. The FV will be visualized with B-mode ultrasound 2-5 cm below the level of the inguinal ligament where the femoral artery is best palpated, without applying any pressure that may affect the FV diameter.; Diagnostic test: Supine Position; All ultrasonography (USG) procedures will be performed by the same anesthesiologist using a Ultrasound device before the start of spinal anesthesia (SA) and after baseline blood pressure and heart rate have been measured. Patients will be placed in supine position. After at least 3 minutes in each position, ultrasound of the inferior vena cava (IVC) and femoral vein (FV) will be performed. The oblique probe will be placed below the xiphoid. Anteroposterior diameters and peak velocities of the IVC will be measured 2-3 cm below the IVC-right atrium For standardization purposes, measurements of the right femoral vein will be used in the study. The FV will be visualized with B-mode ultrasound 2-5 cm below the level of the inguinal ligament where the femoral artery is best palpated, without applying any pressure that may affect the FV diameter.; Diagnostic test: Left Lateral Tilt Position; All ultrasonography (USG) procedures will be performed by the same anesthesiologist using a Ultrasound device before the start of spinal anesthesia (SA) and after baseline blood pressure and heart rate have been measured. Patients will be placed in left lateral tilt (LLT) position. After at least 3 minutes in each position, ultrasound of the inferior vena cava (IVC) and femoral vein (FV) will be performed. The oblique probe will be placed below the xiphoid. Anteroposterior diameters and peak velocities of the IVC will be measured 2-3 cm below the IVC-right atrium For standardization purposes, measurements of the right femoral vein will be used in the study. The FV will be visualized with B-mode ultrasound 2-5 cm below the level of the inguinal ligament where the femoral artery is best palpated, without applying any pressure that may affect the FV diameter.
Active Comparator: Left Lateral Tilt Position; All ultrasonography (USG) procedures will be performed by the same anesthesiologist using a Ultrasound device before the start of spinal anesthesia (SA) and after baseline blood pressure and heart rate have been measured. Patients will be placed in left lateral tilt (LLT) positions. After at least 3 minutes in each position, ultrasound of the inferior vena cava (IVC) and femoral vein (FV) will be performed. The oblique probe will be placed below the xiphoid. Anteroposterior diameters and peak velocities of the IVC will be measured 2-3 cm below the IVC-right atrium For standardization purposes, measurements of the right femoral vein will be used in the study. The FV will be visualized with B-mode ultrasound 2-5 cm below the level of the inguinal ligament where the femoral artery is best palpated, without applying any pressure that may affect the FV diameter.	Diagnostic test: Supine Position; All ultrasonography (USG) procedures will be performed by the same anesthesiologist using a Ultrasound device before the start of spinal anesthesia (SA) and after baseline blood pressure and heart rate have been measured. Patients will be placed in supine and left lateral tilt (LLT) positions. After at least 3 minutes in each position, ultrasound of the inferior vena cava (IVC) and femoral vein (FV) will be performed. The oblique probe will be placed below the xiphoid. Anteroposterior diameters and peak velocities of the IVC will be measured 2-3 cm below the IVC-right atrium For standardization purposes, measurements of the right femoral vein will be used in the study. The FV will be visualized with B-mode ultrasound 2-5 cm below the level of the inguinal ligament where the femoral artery is best palpated, without applying any pressure that may affect the FV diameter.; Diagnostic test: Supine Position; All ultrasonography (USG) procedures will be performed by the same anesthesiologist using a Ultrasound device before the start of spinal anesthesia (SA) and after baseline blood pressure and heart rate have been measured. Patients will be placed in supine position. After at least 3 minutes in each position, ultrasound of the inferior vena cava (IVC) and femoral vein (FV) will be performed. The oblique probe will be placed below the xiphoid. Anteroposterior diameters and peak velocities of the IVC will be measured 2-3 cm below the IVC-right atrium For standardization purposes, measurements of the right femoral vein will be used in the study. The FV will be visualized with B-mode ultrasound 2-5 cm below the level of the inguinal ligament where the femoral artery is best palpated, without applying any pressure that may affect the FV diameter.; Diagnostic test: Left Lateral Tilt Position; All ultrasonography (USG) procedures will be performed by the same anesthesiologist using a Ultrasound device before the start of spinal anesthesia (SA) and after baseline blood pressure and heart rate have been measured. Patients will be placed in left lateral tilt (LLT) position. After at least 3 minutes in each position, ultrasound of the inferior vena cava (IVC) and femoral vein (FV) will be performed. The oblique probe will be placed below the xiphoid. Anteroposterior diameters and peak velocities of the IVC will be measured 2-3 cm below the IVC-right atrium For standardization purposes, measurements of the right femoral vein will be used in the study. The FV will be visualized with B-mode ultrasound 2-5 cm below the level of the inguinal ligament where the femoral artery is best palpated, without applying any pressure that may affect the FV diameter.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Number of Participants with Post-Spinal Hypotension	Post-Spinal Hypotension Measured by Systolic and Diastolic Blood Pressure and Heart Rate Changes Following Spinal Anesthesia in Supine and Left Lateral Tilt Positions Systolic Blood Pressure, Diastolic Blood Pressure, and Heart Rate are now presented as separate outcome measures, each with its own unit of measure.	40 minute

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Number of Participants with time of onset of maternal hypotension, symptomatic hypotension, incidence of bradycardia, cumulative ephedrine requirements, patient satisfaction	Secondary maternal outcomes recorded from the induction of spinal anesthesia (SA) to delivery include: time of onset of maternal hypotension (time from SA to first hypotension episode); symptomatic hypotension (hypotension with nausea, vomiting, and/or dizziness); severe hypotension (systolic arterial pressure [SAP] <70% of baseline); minimum recorded SAP; cumulative duration of hypotension (total minutes of SAP <90 mmHg or diastolic BP <60 mmHg); minimum heart rate (HR); incidence of bradycardia (HR <50 bpm); atropine use for bradycardia; cumulative ephedrine requirements (total ephedrine dose administered); and patient satisfaction (rated on a Likert scale from 1-5).	24 hours

Collaborators and Investigators

• Sponsor: Mehmet Sarı

Publications and helpful links

General Publications

• Yao SF, Zhao YH, Zheng J, Qian JY, Zhang C, Xu Z, Xu T. The transverse diameter of right common femoral vein by ultrasound in the supine position for predicting post-spinal hypotension during cesarean delivery. BMC Anesthesiol. 2021 Jan 20;21(1):22. doi: 10.1186/s12871-021-01242-8.
• Lal J, Jain M, Rahul, Singh AK, Bansal T, Vashisth S. Efficacy of inferior vena cava collapsibility index and caval aorta index in predicting the incidence of hypotension after spinal anaesthesia- A prospective, blinded, observational study. Indian J Anaesth. 2023 Jun;67(6):523-529. doi: 10.4103/ija.ija_890_22. Epub 2023 Jun 14.

Study record dates

Study Major Dates

• Study Start (Estimated): May 1, 2025
• Primary Completion (Estimated): April 30, 2026
• Study Completion (Estimated): August 31, 2026

Study Registration Dates

• First Submitted: March 10, 2025
• First Submitted That Met QC Criteria: March 13, 2025
• First Posted (Actual): March 25, 2025

Study Record Updates

• Last Update Posted (Actual): March 25, 2025
• Last Update Submitted That Met QC Criteria: March 13, 2025
• Last Verified: March 1, 2025

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Vascular Diseases; Cardiovascular Diseases; Hypotension
• Other Study ID Numbers: 2025/7

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: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No