Orthostatic Hypotension, Spinal Cord Injuries
Conditions
Keywords
Blood Pressure, Low, Hypotension, Postural, Injuries, Spinal Cord, Spinal Cord Transection, Spinal Cord Trauma
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.
Interventions
DRUG1.25 mg enalaprilat IV
an angiotensin converting enzyme (ACE) inhibitor given to lower blood pressure (BP) and measure cerebral blood flow (CBF)
OTHERHead up tilt (HUT)
45 degree head-up tilt to lower blood pressure and measure cerebral blood flow.
Sponsors
VA Office of Research and Development
Study design
Allocation
NON_RANDOMIZED
Intervention model
PARALLEL
Primary purpose
HEALTH_SERVICES_RESEARCH
Masking
NONE
Eligibility
Sex/Gender
ALL
Age
18 Years to 65 Years
Healthy volunteers
Yes
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 * Smoking * Pregnancy
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Systolic Blood Pressure | acute testing | Systolic blood pressure during head-up tilt in subjects with spinal cord injury without drug intervention |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Cerebral Blood Flow | acute testing | Measurement of middle cerebral artery blood flow velocity supine and during head-up tilt |
Countries
United States
Participant flow
Recruitment details
Recruitment has been completed.
Pre-assignment details
All subjects recruited completed all testing procedures.
Participants by arm
| Arm | Count |
|---|---|
| Subjects With Spinal Cord Injury Subjects with spinal cord injury underwent a 45 degree head-up tilt maneuver to lower blood pressure and monitor cerebral blood flow on 2 study visits. The first visit subject underwent the head-up tilt maneuver without drug and on the second visits subject underwent the head-up tilt maneuver following oral administration of an angiotensin converting enzyme inhibitor (ACE: 1.25 mg enalaprilat). | 19 |
| Non-spinal Cord Injured Subjects Non-spinal cord injured subjects underwent a 45 degree head-up tilt maneuver to lower blood pressure and monitor cerebral blood flow on 2 study visits. The first visit subject underwent the head-up tilt maneuver without drug and on the second visits subject underwent the head-up tilt maneuver following oral administration of an angiotensin converting enzyme inhibitor (ACE: 1.25 mg enalaprilat). | 11 |
| Total | 30 |
Baseline characteristics
| Characteristic | Non-spinal Cord Injured Subjects | Subjects With Spinal Cord Injury | Total |
|---|---|---|---|
| Age, Categorical <=18 years | 0 Participants | 0 Participants | 0 Participants |
| Age, Categorical >=65 years | 0 Participants | 0 Participants | 0 Participants |
| Age, Categorical Between 18 and 65 years | 11 Participants | 19 Participants | 30 Participants |
| Age, Continuous | 35 years STANDARD_DEVIATION 12 | 41 years STANDARD_DEVIATION 11 | 39 years STANDARD_DEVIATION 12 |
| Region of Enrollment United States | 11 participants | 19 participants | 30 participants |
| Sex: Female, Male Female | 2 Participants | 3 Participants | 5 Participants |
| Sex: Female, Male Male | 9 Participants | 16 Participants | 25 Participants |
Adverse events
| Event type | EG000 affected / at risk | EG001 affected / at risk | EG002 affected / at risk | EG003 affected / at risk |
|---|---|---|---|---|
| deaths Total, all-cause mortality | — / — | — / — | — / — | — / — |
| other Total, other adverse events | 0 / 19 | 0 / 11 | 0 / 19 | 0 / 11 |
| serious Total, serious adverse events | 0 / 19 | 0 / 11 | 0 / 19 | 0 / 11 |
Outcome results
Primary
Systolic Blood Pressure
Systolic blood pressure during head-up tilt in subjects with spinal cord injury without drug intervention
Time frame: acute testing
Population: convenience sample
| Arm | Measure | Value (MEAN) | Dispersion |
|---|---|---|---|
| ARM 1 | Systolic Blood Pressure | 123 mmHg | Standard Deviation 37 |
| ARM 2 | Systolic Blood Pressure | 125 mmHg | Standard Deviation 15 |
| ARM 3 | Systolic Blood Pressure | 119 mmHg | Standard Deviation 26 |
| ARM 4 | Systolic Blood Pressure | 122 mmHg | Standard Deviation 14 |
Secondary
Cerebral Blood Flow
Measurement of middle cerebral artery blood flow velocity supine and during head-up tilt
Time frame: acute testing
| Arm | Measure | Value (MEAN) | Dispersion |
|---|---|---|---|
| ARM 1 | Cerebral Blood Flow | 45.95 cm/sec | Standard Deviation 8.71 |
| ARM 2 | Cerebral Blood Flow | 42.52 cm/sec | Standard Deviation 15.69 |
| ARM 3 | Cerebral Blood Flow | 46.93 cm/sec | Standard Deviation 7.66 |
| ARM 4 | Cerebral Blood Flow | 37.38 cm/sec | Standard Deviation 4.44 |