Carotid Doppler Ultrasound for the Measurement of Intravascular Volume Status

January 9, 2020 updated by: Yale University

Carotid Doppler Ultrasound for the Measurement of Intravascular Volume Status During Lower Body Negative Pressure Simulation

Ultrasound represents an attractive non-invasive method to assess hemodynamic status. Understanding dynamic changes in hemodynamics in situations such as hypovolemia, sepsis, and cardiogenic shock can potentially help improve patient care. However, the inter-rater reliability and accuracy of how various ultrasound measurements reflect dynamic changes in physiology remains incompletely understood. Overall our aims are to investigate the use of ultrasound in a controlled setting, specifically using lower body negative pressure (LBNP), which can simulate hypovolemia at varied levels in human volunteers.

Aim 1: To determine the change in carotid blood flow (measured by velocity time integral, VTI) in subjects undergoing simulated hypovolemia at LBNP levels that precede vital sign changes.

Hypothesis: Carotid VTI will demonstrate significant changes that precede vital sign changes in simulated hypovolemia.

Aim 2: To compare transcranial color Doppler indices of cerebral blood flow with carotid blood flow, as assessed by VTI of the common carotid artery.

Hypothesis: Changes in transcranial color Doppler indices of cerebral blood flow will be mirrored by changes in carotid blood flow, indicating carotid VTI is an adequate surrogate for measuring cerebral blood flow in variable states of central hypovolemia. However, if cerebral blood flow remains more constant than carotid blood flow throughout varying levels of hypovolemia, our assumption is that cerebral autoregulation alters the relationship between carotid and cerebral blood flow. The more complex procedure of Transcranial Doppler ultrasound (TCD) must be performed to obtain valid assessments of cerebral blood flow.

Study Overview

Status

Completed

Conditions

Intervention / Treatment

Detailed Description

Study Design: This is a prospective laboratory study using human volunteers.

Study Setting and Subjects: The study will take place in The John B. Pierce Laboratory where volunteers will be subjected to lower body negative pressure using the on-site LBNP chamber.

Protocol: Study subjects will be instructed to refrain from caffeine, alcohol, or cigarettes within 12 hours of the protocol, but will otherwise be allowed their routine oral intake prior to enrollment. The chamber is constructed of a sealed wood and acrylic box that is connected to a vacuum. Subjects will be placed into the chamber, which is sealed to the level of their pelvis by a neoprene skirt. Chamber pressure is transduced to an electronic digital manometer. The pressure in the chamber will reduced rapidly and held for 15-minute intervals at -5, -10, -15, and -20 mm Hg. If the subject becomes lightheaded, nauseated, or does not tolerate the test run in any way; negative pressure will be stopped.

Subjects will be monitored with continuous electrocardiogram monitoring, a standard automated blood pressure cuff, and a noninvasive beat-to-beat hemodynamic monitor (Finometer, Finapres Medical Systems, Amsterdam, The Netherlands). All carotid ultrasound measurements will be performed by specifically trained emergency physicians, using a Philips ultrasound machine (Philips Medical Systems, Andover, MA) equipped with phased and linear array probes programmed with Doppler capability. For transcranial Doppler imaging, we will use a 5- to 1-MHz sector array transducer and an Iu-22 ultrasound system (Philips Healthcare, Best, the Netherlands). Duplex sonography will be performed at the lower end of the frequency range (1-2 MHz) for better sound wave penetration of selected bone windows. For both the common carotid artery and transcranial portion of this study, we will obtain spectral Doppler waveform tracings and record measurements of corresponding vessel diameters. We will use data generated from software analysis of these spectral tracings to calculate hemodynamic parameters of interest to our study. Calculations are based on Bernoulli's principles of fluid dynamics.

Study Type

Interventional

Enrollment (Actual)

29

Phase

  • Not Applicable

Contacts and Locations

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

Study Locations

  • United States
    • Connecticut
      • New Haven, Connecticut, United States, 06519
        • John B. Pierce Laboratory

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

18 years to 60 years (Adult)

Accepts Healthy Volunteers

No

Genders Eligible for Study

All

Description

Inclusion criteria:

  1. Generally healthy
  2. Able to provide informed consent
  3. Over 18 years of age

Exclusion criteria:

  1. Non-English speaking or decisionaly impaired
  2. Significant medical illness (as determined by the study physician, JC)
  3. Taking vasoactive medications
  4. Older than 60 years of age
  5. Inability to lie flat for prolonged period
  6. Severe claustrophobia
  7. Pregnant

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

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

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Subjects
Lower Body Negative Pressure
Other: Point of Care Ultrasound

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
changes in carotid blood flow (measured by velocity time integral, VTI) in subjects undergoing simulated hypovolemia
Time Frame: over the course of 1-2 hours during which subjects will undergo incremental changes in lower body negative pressure
We will attach adhesive electrodes to your chest which allow us to monitor and record your vital signs. You will lie on your back on a table with the lower half of your body enclosed in a box. The box has a vacuum that creates suction and causes blood to pool in your legs and feet. Next you will do a Lower Body Negative Pressure test. For this test, you will lie with your lower body in the box while we apply increasing levels of suction, over 4 different intervals, lasting 2 minutes each. We will repeat the suction for longer times at each interval and obtain ultrasound images of blood vessels in your head and neck. Each interval may last up to 20 minutes for a total of up to 80 minutes time spent in the chamber.
over the course of 1-2 hours during which subjects will undergo incremental changes in lower body negative pressure

Collaborators and Investigators

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

Sponsor

Yale University

Investigators

  • Principal Investigator: Jill C Crosby, MD, MHS, Yale School of Medicine

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

September 1, 2016

Primary Completion (Actual)

July 1, 2018

Study Completion (Actual)

January 1, 2020

Study Registration Dates

First Submitted

September 14, 2016

First Submitted That Met QC Criteria

September 14, 2016

First Posted (Estimate)

September 20, 2016

Study Record Updates

Last Update Posted (Actual)

January 13, 2020

Last Update Submitted That Met QC Criteria

January 9, 2020

Last Verified

January 1, 2020

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • 1608018234

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

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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