Minimum Effective Volume of Crystalloid Co-Loading to Prevent Spinal Anesthesia-Induced Hypotension in Cesarean Section

NCT ID: NCT07324512

Last Updated: 2026-01-07

Basic Information

• Recruitment Status: NOT_YET_RECRUITING
• Clinical Phase: NA
• Total Enrollment: 45 participants
• Study Classification: INTERVENTIONAL
• Study Start Date: 2025-12-27
• Study Completion Date: 2026-06-30

Brief Summary

The goal of this clinical trial is to find the minimum effective volume of IV crystalloid that should be given with phenylephrine to prevent hypotension caused by spinal anesthesia in healthy, term pregnant adults having elective cesarean delivery.

The main questions are:

What is the minimum effective volume (MEV90, mL/kg) of crystalloid co-loading that prevents spinal-anesthesia-induced hypotension in ≥90% of participants?

What maternal side effects and newborn outcomes occur with this strategy (e.g., nausea/vomiting, need for extra vasopressors, total fluids/blood loss, Apgar scores, and umbilical cord blood gases)?

There is no separate comparison group; this is a single-arm, adaptive dose-finding study.

Participants will:

Receive a predefined volume of IV crystalloid over ~10 minutes during spinal anesthesia while phenylephrine is infused. Have blood pressure and symptoms monitored; receive rescue treatment if needed. Allow the next participant's fluid volume to be adjusted based on whether hypotension occurred (biased-coin design). Be followed through postoperative day 2 for maternal and newborn outcomes.

Conditions

Spinal Induced Hypotension in Cesarean Delivery

Study Design

• Allocation Method: NA
• Intervention Model: SINGLE_GROUP
• Primary Study Purpose: PREVENTION
• Blinding Strategy: NONE

Study Groups

Crystalloid Co-Loading

Participants undergo spinal anesthesia for elective cesarean delivery. Immediately after intrathecal injection, a predefined volume of balanced crystalloid (co-loading) is infused over \~10 minutes while a prophylactic phenylephrine infusion is initiated per protocol. The crystalloid volume for each successive participant is adjusted using a biased-coin up-and-down algorithm to identify the minimum effective volume that prevents spinal-anesthesia-induced hypotension in ≥90% of patients (MEV90, mL/kg). Blood pressure is monitored frequently; rescue phenylephrine and/or fluids are permitted to maintain predefined blood pressure ranges. Maternal adverse events and neonatal outcomes are recorded through postoperative day 2.

Group Type: EXPERIMENTAL

Intravenous Crystalloid Co-Loading

Intervention Type: OTHER

Balanced crystalloid is infused intravenously immediately after intrathecal injection as a co-load. A predefined volume (mL/kg) is administered over \~10 minutes. The volume for successive participants is adapted by a biased-coin up-and-down algorithm to estimate the minimum effective volume (MEV90) that prevents spinal-anesthesia-induced hypotension. Rescue fluids are allowed per protocol.

Interventions

Intravenous Crystalloid Co-Loading

Balanced crystalloid is infused intravenously immediately after intrathecal injection as a co-load. A predefined volume (mL/kg) is administered over \~10 minutes. The volume for successive participants is adapted by a biased-coin up-and-down algorithm to estimate the minimum effective volume (MEV90) that prevents spinal-anesthesia-induced hypotension. Rescue fluids are allowed per protocol.

Intervention Type: OTHER

Eligibility Criteria

Inclusion Criteria

• Pregnant adults ≥19 years scheduled for elective cesarean delivery under spinal anesthesia
• Term pregnancy (≥37 weeks' gestation)

Exclusion Criteria

• Emergency cesarean delivery
• Hypertensive disorders of pregnancy (preeclampsia/eclampsia) or hypertension
• Multiple gestation
• Body weight <50 kg or BMI >35 kg/m²
• Renal impairment or eGFR ≤90 mL/min/1.73 m²
• Heart failure or other heart disease
• History of bronchial asthma or other pulmonary disease

• Minimum Eligible Age: 19 Years
• Eligible Sex: FEMALE
• Accepts Healthy Volunteers: Yes

Sponsors

Seoul National University Hospital

OTHER

Sponsor Role: lead

Responsible Party

Responsibility Role: SPONSOR

Other Identifiers

2508-038-1665

Identifier Type: -

Identifier Source: org_study_id