Systemic Hemodynamics and Cerebral Blood Flow in Persons With Tetraplegia
Overview
- Phase
- Not Applicable
- Intervention
- Head up tilt (HUT)
- Conditions
- Orthostatic Hypotension
- Sponsor
- VA Office of Research and Development
- Enrollment
- 30
- Locations
- 1
- Primary Endpoint
- Systolic Blood Pressure
- Status
- Completed
- Last Updated
- last year
Overview
Brief Summary
The purpose of this study is to determine how blood pressure and blood flow are controlled during head-up tilt in a semi-upright position. In this investigation we are studying blood pressure and blood flow to the brain, with and without a medication which lowers blood pressure (Vasotec). We will determine how persons with a spinal cord injury are able to maintain blood flow to the brain (not get dizzy) as they assume a more upright position and their blood pressure decreases.
Detailed Description
Individuals with tetraplegia lack normal sympathetic nervous system regulation of blood pressure and, therefore, relative hypotension is a common occurrence. This hypotension may be more pronounced with postural stress. Loss in mental acuity and sometimes even consciousness is an associated symptom of postural hypotension in individuals with tetraplegia. There is some evidence to suggest that although mean arterial blood pressure (MAP) is relatively low in these individuals, middle cerebral arterial blood flow (CBF) may be maintained. Consequently, individuals with chronic tetraplegia often compensate and are stable in the seated upright position. Autoregulation of CBF has been defined as the stability of cerebral blood flow throughout a range of systemic blood pressures (MAP). This proposal will examine systemic hemodynamics and middle cerebral artery blood flow during HUT with and without Vasotec, an angiotensin II inhibitor. By partially or completely ablating the renin-angiotensin system, which is postulated to play a major role in blood pressure regulation, the potential dissociation between systemic blood pressure and middle cerebral artery blood flow, in individuals with tetraplegia, may be demonstrated. The aim is to determine whether persons with chronic tetraplegia are able to maintain similar CBF, or similar CBF changes, as able-bodied controls despite a greater decrease in MAP to the same hypotensive challenge. The relationship between MAP and CBF has not been defined in this population. Understanding this relationship may lead to improved screening and treatment for prevention of postural hypotension in persons with tetraplegia.
Investigators
Eligibility Criteria
Inclusion Criteria
- •Duration of spinal cord injury (SCI) at least 1 year
- •Level of SCI C4-8 and T6 and below
- •matched non-SCI subjects
- •Chronological age between 18-65 years
- •Euhydration: Subjects will be instructed to avoid caffeine and alcohol and to maintain normal salt and water intake for several days prior to study.
Exclusion Criteria
- •Known heart and/or blood vessel disease
- •Dehydration
- •High blood pressure
- •Kidney disease
- •Diabetes mellitus
- •Prescribed ACE inhibitors
- •Acute Infection
- •Pregnancy
Arms & Interventions
ARM 1
Head-up tilt maneuver without drug in subjects with spinal cord injury
Intervention: Head up tilt (HUT)
ARM 3
Head-up tilt maneuver without drug in able-bodied controls
Intervention: Head up tilt (HUT)
ARM 2
Head-up tilt maneuver with an angiotensin converting enzyme inhibitor (1.25 mg enalaprilat) in subjects with spinal cord injury
Intervention: 1.25 mg enalaprilat IV
ARM 2
Head-up tilt maneuver with an angiotensin converting enzyme inhibitor (1.25 mg enalaprilat) in subjects with spinal cord injury
Intervention: Head up tilt (HUT)
ARM 4
Head-up tilt maneuver with an angiotensin converting enzyme inhibitor (1.25 mg enalaprilat) in able-bodied controls.
Intervention: 1.25 mg enalaprilat IV
ARM 4
Head-up tilt maneuver with an angiotensin converting enzyme inhibitor (1.25 mg enalaprilat) in able-bodied controls.
Intervention: Head up tilt (HUT)
Outcomes
Primary Outcomes
Systolic Blood Pressure
Time Frame: acute testing
Systolic blood pressure during head-up tilt in subjects with spinal cord injury without drug intervention
Secondary Outcomes
- Cerebral Blood Flow(acute testing)