Correlation of Carotid Flow Time and Cardiac Output.

Study Overview
=================
Brief Summary
-----------------
Assessment of common carotid artery flow is more easily done and can be taught more broadly than transthoracic echocardiography, providing a greater number of clinicians a tool to assess volume responsiveness. These assessments are of great importance to patients with COVID-19, who often present with hypotension requiring fluids, which must be balanced against limiting fluid administration to minimize pulmonary edema.

Detailed Description
-----------------
Optimizing volume status for patients in shock is of critical importance to their outcomes, both in the provision of helpful, and avoidance of harmful fluid volumes. As such, much work has been done to develop and assess measures of volume responsiveness; that is, tests that indicate whether additional fluid administration will increase cardiac output by at least 10%. The passive leg raise (PLR) providing a reversible auto-bolus has been demonstrated to be the most predictive assessment of fluid responsiveness. Recent studies of changes in carotid artery blood flow suggest it can be used as a surrogate for changes in cardiac output with moderate reliability. This has been assessed in several populations with anticipated changes in volume status (e.g. before/after blood donation), and more recently assessed by Sidor et al. against several preload augmenting maneuvers. Interestingly, while decreasing preload resulted in a decrease in cardiac output and systolic carotid blood flow, it did not result in a decrease in corrected carotid flow time, although a PLR produced an expected increase in all measures. In our study we seek to validate these results, questioning if there is a lower limit of corrected carotid flow time that de-couples the relationship between carotid systolic flow and corrected carotid flow time.

Official Title
-----------------
Correlation of Carotid Flow Time and Cardiac Output With Preload Augmentation in Patients With COVID-19.

Conditions
-----------------
Volume Responsiveness

Intervention / Treatment
-----------------
* Procedure: Carotid Artery Ultrasound Measure


Participation Criteria
=================
Eligibility Criteria
-----------------
Inclusion Criteria: Adult patient admitted to hospital with diagnosed COVID-19, on up to 6L oxygen, and able to undergo leg compression testing and passive leg raise. Exclusion Criteria: known cardiac disease, carotid atherosclerosis, prior right-sided neck surgery, chest wall deformity, or deep-venous thrombosis identified on admission

Ages Eligible for Study
-----------------
Minimum Age: 18 Years
Maximum Age: 80 Years

Sexes Eligible for Study
-----------------
All

Study Plan
=================
How is the study designed?
-----------------

Arms and Interventions

| Intervention/Treatment |
| --- |
|Procedure: Carotid Artery Ultrasound Measure|Cardiac output will be assessed by measuring the LVOT diameter in parasternal long-axis window and the LVOT VTI in apical-four window. Carotid artery flow will be measured on the right neck 1-2cm from the bifurcation of the common carotid artery. All measurements will be taken with participants supine and the head of the bed elevated to 45°. measures all at 3 minute intervals. One-leg compression test: Thigh-sized blood pressure cuff inflated to 60mmHg on middle part of one thigh for 60 seconds. LVOT and CCA measurements taken separately. Two-leg compression test: Thigh-sized blood pressure cuff inflated on middle part of both thighs for 60 seconds. LVOT and CCA measurements taken separately. Passive leg raise test: Bed adjusted to place participant at 0° and legs elevated at 45° by use of pillows. After 1 minute, measurements repeated. LVOT and CCA measurements taken separately.|

What is the study measuring?
-----------------
Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in measured LVOT VTI by bedside echocardiography | Measurements for this parameter will be obtained at baseline, following one-leg and two-leg compression tests, and following passive leg raise | Through study completion, up to 1 year | 
| Changed in corrected carotid artery flow time as measured by bedside carotid artery ultrasonography. | Measurements for this parameter will be obtained at baseline, following one-leg and two-leg compression tests, and following passive leg raise. | Through study completion, up to 1 year | 

 Terms related to the study
=================
Keywords Provided by Centre Hospitalier Valida
-----------------
volume responsiveness, ultrasound, fluid responsiveness