Sonographic Safety Margins of Subclavian Vein: Effect of View and Arm Position

April 29, 2026 updated by: Jun-Young Park, Asan Medical Center

Observational Ultrasound Study of Subclavian Vein Anatomy: Comparison of Safety Margins Between Supraclavicular and Infraclavicular Positions According to Arm Position

The purpose of this observational study is to evaluate and compare the anatomical safety margins of the subclavian vein using ultrasound. Medical professionals commonly use the subclavian vein to insert central venous catheters, but nearby vulnerable structures, such as the lung and artery, can be at risk during the procedure.

This study investigates two different ultrasound probe positions: supraclavicular (above the collarbone) and infraclavicular (below the collarbone). It also examines how changing the patient's arm position (from resting in a neutral position to being raised at a 90-degree angle) affects the distance between the vein and these vulnerable structures.

Participants are adult patients scheduled for surgery under general anesthesia who already require ultrasound-guided vascular access. Immediately after falling asleep from anesthesia, researchers will perform a brief 3 to 5-minute ultrasound scan of the collarbone area. This is a strictly non-invasive imaging study; no research-related needle punctures or catheter insertions will be performed. The findings aim to provide robust anatomical evidence to make future vascular procedures safer for patients.

Study Overview

Status

Not yet recruiting

Conditions

Intervention / Treatment

Detailed Description

Central venous catheterization via the subclavian vein (SCV) is clinically favored due to its lower infection and thrombosis rates. However, traditional landmark-guided approaches carry the risk of mechanical complications, including pneumothorax and inadvertent arterial puncture. While real-time ultrasound guidance is strongly recommended to minimize these risks, there is an ongoing debate regarding the optimal probe position-specifically, the supraclavicular (SC) versus the infraclavicular (IC) view. Furthermore, clinical practitioners frequently utilize arm abduction to facilitate venous access, yet its dynamic effect on the anatomical safety margin (the distance between the SCV and adjacent vulnerable structures like the subclavian artery [SCA] and pleura) remains insufficiently quantified.

This prospective, non-invasive observational study aims to address this knowledge gap. The study will enroll 55 adult patients scheduled to undergo

Study Protocol:

Timing: Immediately following the induction of general anesthesia, during the standard pre-procedural preparation period, a brief (approximately 3 to 5 minutes) ultrasound assessment will be conducted.

Imaging: An investigator will obtain short-axis ultrasound views of the SCV from both the SC and IC positions.

Positioning: In each ultrasound view, measurements will be recorded under two different patient arm positions: neutral (adducted alongside the torso) and 90-degree abduction.

Data Acquisition: All ultrasound images will be captured at the end-expiratory phase and saved for offline analysis.

Safety: The study involves solely non-invasive sonographic observation; no research-specific needle puncture, cannulation, or catheterization will be performed. Routine scheduled clinical care and procedures will proceed immediately after the brief image acquisition is complete.

By analyzing sonographic parameters such as the SCV-SCA distance, vessel cross-sectional areas, depth to the pleura, and the SCV-SCA overlap index, this study seeks to elucidate the most secure anatomical window. Ultimately, the data will establish safer, evidence-based guidelines for patient positioning and ultrasound probe placement during SCV access.

Study Type

Observational

Enrollment (Estimated)

55

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Locations

  • South Korea
      • Seoul, South Korea, 05505
        • Asan Medical Center

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Sampling Method

Non-Probability Sample

Study Population

Need for ultrasound-guided vascular access for general anesthesia

Description

Inclusion Criteria:

  • Patients requiring ultrasound-guided vascular procedures.
  • Age between 20 and 79 years.
  • Patients who have voluntarily provided written informed consent for this clinical study.
  • American Society of Anesthesiologists (ASA) physical status classification I, II, or III.

Exclusion Criteria:

  • Anatomical variations of the clavicle (e.g., history of clavicle fracture).
  • Suspected thrombosis at the target site.
  • Known anatomical abnormalities of the subclavian vein or artery.
  • Inability to abduct the arm (e.g., due to shoulder joint abnormalities).
  • Patient refusal to participate.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

Cohorts and Interventions

Group / Cohort
Intervention / Treatment
Observation Group
Adult patients undergoing general anesthesia who are scheduled for ultrasound-guided vascular catheterization.
Other: Non-invasive sonographic observation
Non-invasive ultrasound measurement of anatomical safety margins of the subclavian vein and adjacent structures, comparing supraclavicular and infraclavicular views in neutral and abducted arm positions.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Shortest Distance Between the Subclavian Vein (SCV) and Subclavian Artery (SCA)
Time Frame: Immediately after the induction of general anesthesia (within 3 to 5 minutes)
The shortest anatomical distance between the SCV and SCA is measured in the neutral arm position to evaluate the safety margin. The difference between the supraclavicular (SC) and infraclavicular (IC) views will be analyzed using a paired t-test or Wilcoxon signed-rank test.
Immediately after the induction of general anesthesia (within 3 to 5 minutes)

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Relative Position of the Subclavian Artery (SCA) to the Subclavian Vein (SCV)
Time Frame: Immediately after the induction of general anesthesia (within 3 to 5 minutes)
A nominal variable describing the anatomical location of the SCA relative to the SCV (e.g., medial, posteromedial, posterior). The distribution changes according to the probe view (SC vs. IC) and arm position (neutral vs. abduction) will be compared using Generalized Estimating Equations (GEE).
Immediately after the induction of general anesthesia (within 3 to 5 minutes)
Sonographic Continuous Variables of the SCV and Adjacent Structures
Time Frame: Immediately after the induction of general anesthesia (within 3 to 5 minutes)
The following continuous variables will be measured: 1) distance between SCV and SCA, 2) distance from skin to the anterior and posterior walls of SCV, 3) distance from SCV posterior wall to the pleura. These parameters will be analyzed using a two-way repeated measures ANOVA to assess the effects of the probe view (SC vs. IC) and arm position (neutral vs. abduction).
Immediately after the induction of general anesthesia (within 3 to 5 minutes)
Sonographic Cross-Sectional Area (CSA) Variables of the SCV and Adjacent Structures
Time Frame: Immediately after the induction of general anesthesia (within 3 to 5 minutes)
The following continuous variables regarding area and dimension will be measured: 1) transverse length and cross-sectional area (CSA) of the SCV, and 2) CSA of the SCA. These parameters will be analyzed using a two-way repeated measures ANOVA to assess the effects of the probe view (SC vs. IC) and arm position (neutral vs. abduction).
Immediately after the induction of general anesthesia (within 3 to 5 minutes)
Sonographic Proportion and Index Variables of the SCV and Adjacent Structures
Time Frame: Immediately after the induction of general anesthesia (within 3 to 5 minutes)
The following continuous variables regarding proportions will be measured: 1) SCV-SCA overlap index (%), and 2) clavicle shadowing proportion (%). These parameters will be analyzed using a two-way repeated measures ANOVA to assess the effects of the probe view (SC vs. IC) and arm position (neutral vs. abduction).
Immediately after the induction of general anesthesia (within 3 to 5 minutes)

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Asan Medical Center

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Estimated)

April 23, 2026

Primary Completion (Estimated)

July 15, 2026

Study Completion (Estimated)

July 15, 2026

Study Registration Dates

First Submitted

April 22, 2026

First Submitted That Met QC Criteria

April 22, 2026

First Posted (Actual)

April 29, 2026

Study Record Updates

Last Update Posted (Actual)

May 5, 2026

Last Update Submitted That Met QC Criteria

April 29, 2026

Last Verified

April 1, 2026

More Information

Terms related to this study

Other Study ID Numbers

  • 2026-0533

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

IPD Plan Description

Individual participant data (IPD) will not be shared to protect patient privacy and confidentiality, in accordance with the Institutional Review Board (IRB) regulations. Only aggregated and anonymized data will be presented in the final publication.

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

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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