Ultrasound-guided Versus Landmark-based Spinal Anesthesia in Obese Parturients Undergoing Cesarean Section (USLMCSEOB)

Ultrasound-guided Versus Landmark-based Spinal Anesthesia in Obese Parturients Undergoing Cesarean Section: a Randomized Controlled Trial

Spinal anesthesia is the most commonly used technique for cesarean section. However, in obese parturients, identification of the optimal puncture site using anatomical landmark palpation can be challenging due to altered anatomy. Ultrasound has been proposed as a tool to improve localization of the puncture site.

This study is a prospective randomized controlled trial including 100 obese parturients undergoing cesarean section under spinal anesthesia. Participants are randomly assigned to one of two groups: an ultrasound group, in which the puncture site is identified using preprocedural ultrasound, and a landmark group, in which the puncture site is determined using anatomical landmark palpation.

The primary outcome is the first-attempt success rate. Secondary outcomes include the number of attempts, needle redirections, need for rescue interventions, incidence of adverse events during puncture, and procedural times.

Study Overview

• Status: Completed
• Conditions: Obesity; Cesarean Section
• Intervention / Treatment: Procedure: Ultrasound-guided preprocedural marking; Procedure: Landmark-based palpation

Detailed Description

This prospective randomized controlled trial aims to evaluate the effectiveness of preprocedural ultrasound-guided marking compared with the conventional landmark palpation technique for spinal anesthesia in obese parturients undergoing cesarean section.

A total of 100 parturients with a body mass index (BMI) ≥ 30 kg/m² are randomly assigned to either the ultrasound group or the landmark group. In the ultrasound group, the puncture site is identified using preprocedural ultrasound to determine the optimal intervertebral space and needle insertion trajectory. In the landmark group, the puncture site is determined using anatomical landmarks.

The primary outcome is the first-attempt success rate, defined as successful cerebrospinal fluid return without needle redirection. Secondary outcomes include the number of puncture attempts, needle redirections, need for rescue interventions, incidence of adverse events (paresthesia and vascular puncture), and procedural times (site identification time, puncture time, and total procedural time).

This study aims to determine whether ultrasound guidance improves the performance and safety of spinal anesthesia in obese parturients.

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

Contacts and Locations

Study Locations

• Peru
  • Lima Province
    • Lima, Lima Province, Peru, 15001
      • National Maternal and Perinatal Institute

Participation Criteria

Eligibility Criteria

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

Description

Inclusion Criteria:

• Age ≥ 18 years
• Pregnant women undergoing cesarean section
• Body mass index (BMI) ≥ 30 kg/m² at the time of cesarean section
• Scheduled for cesarean section under spinal anesthesia

Exclusion Criteria:

• Congenital spinal deformities
• History of spinal surgery
• Coagulopathy
• Infection at the puncture site
• Allergy to local anesthetics
• Emergency cesarean section (NICE category 1)

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: Ultrasound-guided group; Preprocedural ultrasound was used to identify and mark the optimal puncture site in obese parturients undergoing cesarean section (n = 50).	Procedure: Ultrasound-guided preprocedural marking; Preprocedural ultrasound is used to identify and mark the optimal puncture site before spinal anesthesia.
Active Comparator: Landmark-based group; The puncture site was identified using anatomical landmark palpation in obese parturients undergoing cesarean section (n = 50)	Procedure: Landmark-based palpation; The puncture site is identified using anatomical landmark palpation before spinal anesthesia.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
First-attempt success rate of spinal anesthesia	Successful cerebrospinal fluid return after the first needle insertion without redirection.	During the spinal anesthesia procedure

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Number of puncture attempts	Total number of needle insertions required to achieve successful spinal anesthesia	During the spinal anesthesia procedure
Number of needle redirections	Number of needle redirections during a single puncture attempt	During the spinal anesthesia procedure
Need for rescue intervention	Requirement of assistance by a more experienced operator to complete the procedure	During the spinal anesthesia procedure
Incidence of paresthesia	Occurrence of paresthesia during needle insertion	During the spinal anesthesia procedure
Incidence of vascular puncture	Occurrence of vascular puncture during needle insertion	During the spinal anesthesia procedure
Total procedure time	Time from initial identification of the puncture site to successful cerebrospinal fluid return	During the spinal anesthesia procedure
Puncture time	Time from needle insertion to successful cerebrospinal fluid return	During the spinal anesthesia procedure

Collaborators and Investigators

• Sponsor: Instituto Nacional Materno Perinatal, Peru
• Investigators: Principal Investigator: Eddisson R Quispe Pilco, MD, National Maternal and Perinatal Institute

Publications and helpful links

General Publications

• Khoo AK, Huynh A, Pelecanos A, Eley VA. Does preprocedural ultrasound increase first-pass success in obese adults undergoing neuraxial anesthesia? A systematic review. Health Sci Rep. 2024;7:e70039.
• Zhang Y, Peng M, Wei J, et al. Ultrasound-guided versus traditional localization in intraspinal anesthesia: a systematic review and network meta-analysis. BMJ Open. 2023;13:e071253
• Li M, Ni X, Xu Z, et al. Ultrasound-assisted technology versus the conventional landmark method in spinal anesthesia for cesarean delivery in obese parturients: a randomized controlled trial. Anesth Analg. 2019;129(1):155-161.
• Perlas A, Chaparro LE, Chin KJ. Lumbar neuraxial ultrasound for spinal and epidural anesthesia: a systematic review and meta-analysis. Reg Anesth Pain Med. 2016;41(2):251-260.

Study record dates

Study Major Dates

• Study Start (Actual): July 1, 2025
• Primary Completion (Actual): January 1, 2026
• Study Completion (Actual): January 1, 2026

Study Registration Dates

• First Submitted: April 9, 2026
• First Submitted That Met QC Criteria: April 17, 2026
• First Posted (Actual): April 24, 2026

Study Record Updates

• Last Update Posted (Actual): April 24, 2026
• Last Update Submitted That Met QC Criteria: April 17, 2026
• Last Verified: April 1, 2026

More Information

Terms related to this study

• Keywords: Obesity; Cesarean section; Spinal anesthesia; Ultrasonography; Neuraxial anesthesia
• Additional Relevant MeSH Terms: Nutrition Disorders; Overnutrition; Body Weight; Overweight; Pathological Conditions, Signs and Symptoms; Nutritional and Metabolic Diseases; Signs and Symptoms; Obesity
• Other Study ID Numbers: 0107-DG-0080-OEAIDE-I

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: URL address will be offered or information will be sent by email.
• IPD Sharing Time Frame: Beginning 3 months after publication and ending 12 months after publication
• IPD Sharing Access Criteria: Access will be granted to researchers who provide a methodologically sound proposal. Proposals should be directed to the corresponding author via email. Data will be shared after approval of the proposal and signing of a data access agreement.
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; SAP; ICF; ANALYTIC_CODE; CSR

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No