Physiologic Study of Cerebral Perfusion

Study Overview
=================
Brief Summary
-----------------
The aim of the study is to measure cerebral perfusion using MRI in healthy subjects (with and without sedation) and in vasopressor-dependent patients

Official Title
-----------------
Physiologic Study of Cerebral Perfusion

Conditions
-----------------
Cerebral Perfusion Pressure, Vasopressor Agents, Shock, Magnetic Resonance Imaging (MRI), Functional

Intervention / Treatment
-----------------
* Drug: Higher doses of vasopressor therapy for a MAP of 75 mmHg
* Drug: Lower doses of vasopressor therapy for a MAP of 65 mmHg
* Drug: Propofol for light sedation


Participation Criteria
=================
Eligibility Criteria
-----------------
Healthy Subjects : Inclusion criteria : being over 18 years old Exclusion criterias : having a positive serum pregnancy test having a contraindication to MRI having a contraindication to receive light sedation with propofol suffering of claustrophobia or of anxiety disorder Shock Subjects : Inclusion criterias : being over 18 years old being hospitalized to the medical intensive care unit of the CHUS Fleurimont being in a stabilized shock state, primarily of distributive etiology having received an appropriate fluid resuscitation, as judged by the attending physician Exclusion criterias : having a different primary etiology of shock than distributive (cardiogenic, hypovolemic, obstructive) needing vasopressor therapy as the result of extracorporeal circulation having known cerebral lesions having an intra-aortic balloon pump being in a palliative or near end-of-life situation having a contraindication to MRI suffering of claustrophobia or of anxiety disorder

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

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

Accepts Healthy Volunteers
-----------------
Accepts Healthy Volunteers

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

Design Details

Primary Purpose: Supportive Care
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: Shock lower Mean Arterial Pressure (MAP)<br>Vasopressor-dependent treated to lower MAP (65 mmHg) | Drug: Lower doses of vasopressor therapy for a MAP of 65 mmHg<br> <br> Drug: Propofol for light sedation<br>* Propofol for light sedation<br>|
| Experimental: Shock higher MAP<br>Vasopressor-dependent treated to higher MAP (75 mmHg) | Drug: Higher doses of vasopressor therapy for a MAP of 75 mmHg<br> <br> Drug: Propofol for light sedation<br>* Propofol for light sedation<br>|
| No Intervention: Healthy participant awake<br>Healthy participant awake | |
| Experimental: Healthy participant sedated<br>Healthy participant Under light sedation | Drug: Propofol for light sedation<br>* Propofol for light sedation<br>|

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

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Global and regional cerebral blood flow | Cerebral blood flow will be measured by the arterial spin labeling technique (ASL) which provides information expressed in mL/100g/min. Using 3-T MRI technology,we will first acquire T1 images of the brain and sub-regions of interest. Thereafter, ASL sequences will be acquired in contiguous slices. The procedure will be followed on sedation and off sedation for healthy volunteers (in random order) and at mean arterial pressure of 65 mmHg and 75 mmHg (in random order) in patients receiving vasopressor therapy. | Within 15 minutes of intervention initiation |