A Study of Blood Pressure and Blood Supply to the Brain in Persons With a Spinal Cord Injury.
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.
Spinal Cord Injuries
Drug: 1.25 mg enalaprilat IV
Other: Head up tilt (HUT)
|Study Design:||Allocation: Non-Randomized
Endpoint Classification: Efficacy Study
Intervention Model: Parallel Assignment
Masking: Open Label
Primary Purpose: Health Services Research
|Official Title:||Systemic Hemodynamics and Cerebral Blood Flow in Persons With Tetraplegia|
- cerebral blood flow and blood pressure [ Time Frame: Cerebral blood flow and blood pressure will be measured every 20 and 10 minutes, respectively during the baseline and post-challenge periods. ] [ Designated as safety issue: No ]The speed of blood flow in the middle cerebral artery will be measured by transcranial doppler as an index of blood flow to the brain. Systemic blood pressure will be measured at the brachial artery. Cerebral blood flow and blood pressure will be measured before, during and after each intervention on each of the 3 visits.
|Study Start Date:||October 2005|
|Study Completion Date:||April 2012|
|Primary Completion Date:||May 2009 (Final data collection date for primary outcome measure)|
Experimental: Arm 1
1.25 mg enalaprilat IV and/or 45 degree HUT to lower BP and measure CBF
Drug: 1.25 mg enalaprilat IV
an ACE inhibitor given to lower BP and measure CBFOther: Head up tilt (HUT)
45 degree HUT to lower BP and measure CBF
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.
|United States, New York|
|VA Medical Center, Bronx|
|Bronx, New York, United States, 10468|
|Principal Investigator:||Jill Wecht, EdD||VA Medical Center, Bronx|