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Trbovich M, Wu Y, Koek W, Zhao J, Kellogg D. Impact of tetraplegia vs. paraplegia on venoarteriolar, myogenic and maximal cutaneous vasodilation responses of the microvasculature: Implications for cardiovascular disease. J Spinal Cord Med 2022; 45:49-57. [PMID: 32496962 PMCID: PMC8890560 DOI: 10.1080/10790268.2020.1761173] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
Abstract
Objective: Cardiovascular disease (CVD) is a leading cause of mortality in persons with SCI. While macrovascular remodeling and function after SCI is well documented, changes in the microvascular structure and function are comparably understudied, but importantly predict CVD risk. Specifically, the integrity of venoarteriolar (VAR), myogenic (MYO) and maximal vasodilation responses are largely unknown after SCI, especially in persons with tetraplegia (TP) at highest risk of CVD. This is the first to examine the differences in VAR (cuff inflation), MYO (limb dependency) and maximal vasodilation responses of the microvasculature between able bodied (AB) versus those with TP and paraplegia (PP).Design: Observational.Setting: Laboratory.Participants: Eight AB, 6 TP, and 8 PP persons.Interventions: One forearm and calf were treated topically with lidocaine 2.5%/prilocaine 2.5% while contralateral limb served as a control. Laser doppler flowmeters were applied over treated and control sites during limb dependency, cuff inflation and local skin heating (Tloc) up to 42°C.Outcome measures: Skin vascular resistance (SkVR) change with cuff inflation and limb dependency and maximal cutaneous vascular conductance (CVC) during local heating.Results: Change in SkVR was not significantly different between groups or extremity (upper vs. lower) during cuff inflation or limb dependency. However, CVC at Tloc 42°C was significantly different in the lower extremity (LE) of TP and PP (P = 0.007, 0.35) compared to AB.Conclusion: Increases in SkVR during cuff inflation (VAR) and limb dependency (VAR and MYO) are unaltered after SCI, however maximal vasodilation in the LE post-SCI is higher than AB persons.
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Affiliation(s)
- Michelle Trbovich
- Department of Rehabilitation Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA,Correspondence to: Michelle Trbovich, Department of Rehabilitation Medicine, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio78229, TX, USA.
| | - Yubo Wu
- Department of Physiology, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
| | - Wouter Koek
- Department of Psychiatry, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
| | - Joan Zhao
- Department of Physiology, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
| | - Dean Kellogg
- Department of Physiology, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
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Sundby ØH, Høiseth LØ, Irgens I, Mathiesen I, Lundgaard E, Haugland H, Weedon-Fekjær H, Sundhagen JO, Sanbæk G, Hisdal J. Intermittent negative pressure applied to the lower limb increases foot macrocirculatory and microcirculatory blood flow pulsatility in people with spinal cord injury. Spinal Cord 2017; 56:382-391. [DOI: 10.1038/s41393-017-0049-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2017] [Revised: 12/02/2017] [Accepted: 12/04/2017] [Indexed: 12/15/2022]
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Estañol B, Rivera AL, Martínez Memije R, Fossion R, Gómez F, Bernal K, Murúa Beltrán S, Delgado-García G, Frank A. From supine to standing: in vivo segregation of myogenic and baroreceptor vasoconstriction in humans. Physiol Rep 2017; 4:4/24/e13053. [PMID: 28039403 PMCID: PMC5210387 DOI: 10.14814/phy2.13053] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2016] [Accepted: 10/30/2016] [Indexed: 11/24/2022] Open
Abstract
Myogenic vascular response is a form of systemic and regional vasoconstriction produced increasing the intra‐arterial pressure by gravity. Here, the vasoconstriction due to the myogenic response, induced by the gravitational action in a dependent limb, is separated from that caused by the baroreceptor reflex. Regional changes of skin blood flow (SBF), total blood volume of the finger (TBVF), pulse pressure (PP), heart rate (HR), systolic, and diastolic blood pressure (BP) were analyzed in 10 healthy young subjects in supine and upright positions. By lowering the arm in supine position, SBF decreased compared to its basal measurement, PR increased, and PP contracted, indicating arterial vasoconstriction that rise BP. TBVF increased, demonstrating an increment in venous volume. HR did not change, reflecting no action of the baroreceptor reflex. In upright position with lowered arm, there was an additional increase in BP variables, demonstrating vasoconstriction. Moreover, BP and HR showed oscillations at 0.1 Hz reflecting the entrance of the baroreceptor reflex. The action of gravity in a dependent limb in supine position induces a regional vasoconstriction and an increase of BP due to activation of the myogenic response, while the baroreceptor reflex or other neural factors do not appear to operate. In the upright position with the arm dependent, there is a further increase in regional vasoconstriction and BP with reciprocal changes in HR, indicating the entrance of the baroreceptor superimposed to the myogenic response. This study demonstrates that the myogenic and baroreceptor vasoconstriction can be separated in vivo.
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Affiliation(s)
- Bruno Estañol
- Laboratorio de Neurofisiología Clínica, Departamento de Neurología y Psiquiatría, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, México City, México.,Centro de Ciencias de la Complejidad, Universidad Nacional Autónoma de México, México City, México
| | - Ana Leonor Rivera
- Centro de Ciencias de la Complejidad, Universidad Nacional Autónoma de México, México City, México .,Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, México City, México
| | - Raúl Martínez Memije
- Departamento de Instrumentación Electromecánica, Instituto Nacional de Cardiología, México City, México
| | - Ruben Fossion
- Centro de Ciencias de la Complejidad, Universidad Nacional Autónoma de México, México City, México.,Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, México City, México
| | - Fermín Gómez
- Laboratorio de Neurofisiología Clínica, Departamento de Neurología y Psiquiatría, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, México City, México
| | - Katherine Bernal
- Laboratorio de Neurofisiología Clínica, Departamento de Neurología y Psiquiatría, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, México City, México
| | - Sofía Murúa Beltrán
- Laboratorio de Neurofisiología Clínica, Departamento de Neurología y Psiquiatría, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, México City, México
| | - Guillermo Delgado-García
- Laboratorio de Neurofisiología Clínica, Departamento de Neurología y Psiquiatría, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, México City, México .,Departamento de Medicina Interna, Hospital Universitario "Dr. José Eleuterio González", Universidad Autónoma de Nuevo León, Monterrey, México
| | - Alejandro Frank
- Centro de Ciencias de la Complejidad, Universidad Nacional Autónoma de México, México City, México.,Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, México City, México.,Colegio Nacional, México City, México
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Improvement in hemodynamic responses to metaboreflex activation after one year of training in spinal cord injured humans. BIOMED RESEARCH INTERNATIONAL 2014; 2014:893468. [PMID: 24809060 PMCID: PMC3997898 DOI: 10.1155/2014/893468] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/07/2013] [Accepted: 02/26/2014] [Indexed: 11/25/2022]
Abstract
Spinal cord injured (SCI) individuals show an altered hemodynamic response to metaboreflex activation due to a reduced capacity to vasoconstrict the venous and arterial vessels below the level of the lesion. Exercise training was found to enhance circulating catecholamines and to improve cardiac preload and venous tone in response to exercise in SCI subjects. Therefore, training would result in enhanced diastolic function and capacity to vasoconstrict circulation. The aim of this study was to test the hypothesis that one year of training improves hemodynamic response to metaboreflex activation in these subjects. Nine SCI individuals were enrolled and underwent a metaboreflex activation test at the beginning of the study (T0) and after one year of training (T1). Hemodynamics were assessed by impedance cardiography and echocardiography at both T0 and T1. Results show that there was an increment in cardiac output response due to metaboreflex activity at T1 as compared to T0 (545.4 ± 683.9 mL·min−1 versus 220.5 ± 745.4 mL·min−1, P < 0.05). Moreover, ventricular filling rate response was higher at T1 than at T0. Similarly, end-diastolic volume response was increased after training. We concluded that a period of training can successfully improve hemodynamic response to muscle metaboreflex activation in SCI subjects.
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Yoshida T, Masani K, Sayenko DG, Miyatani M, Fisher JA, Popovic MR. Cardiovascular Response of Individuals With Spinal Cord Injury to Dynamic Functional Electrical Stimulation Under Orthostatic Stress. IEEE Trans Neural Syst Rehabil Eng 2013; 21:37-46. [DOI: 10.1109/tnsre.2012.2211894] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Gemignani T, Matos-Souza JR, Franchini KG, Nadruz W. Leg blood pressure measured in orthostatic posture is associated with left ventricular mass in normotensive subjects. Am J Hypertens 2012; 25:1083-7. [PMID: 22810843 DOI: 10.1038/ajh.2012.101] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND Changing from a supine to an orthostatic posture is associated with substantial increments in leg blood pressure (BP) levels, which could ultimately influence the hemodynamic burden imposed on the heart. This study investigated the relationship between brachial and leg BP measurements and the left cardiac chamber's structure and assessed the role of body posture changes in this regard. METHODS One hundred and thirty normotensive, nondiabetic, nonsmoking, normolipemic subjects were evaluated by a clinical history, anthropometry, the analysis of metabolic parameters, echocardiography, and the measurement of BP in the arm and the calf in both supine and orthostatic positions. RESULTS Significant correlation coefficients between the leg BP measurements and the cardiac structure were detected, especially between the orthostatic pulse pressure (PP) and the left ventricular (LV) wall thickness (r = 0.38; P < 0.001), the orthostatic PP and the LV mass (r = 0.37; P < 0.001), and the orthostatic systolic BP (SBP) and the left atrial size (r = 0.35; P < 0.001). Stepwise and standard regression analysis adjusted for brachial BP and anthropometric and metabolic variables confirmed that the leg orthostatic PP was independently related to the LV wall thickness and mass. Moreover, the leg orthostatic SBP was associated with the left atrial dimension even after adding the LV mass to the statistical models. Finally, triglyceride levels and body surface area showed significant relationship with leg orthostatic PP and SBP, whereas brachial orthostatic PP and SBP were only associated with age and anthropometric variables. CONCLUSIONS Orthostatic leg BP is independently associated with the cardiac structure in normotensive subjects.
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Snyder KAM, Shamimi-Noori S, Wilson TE, Monahan KD. Age- and limb-related differences in the vasoconstrictor response to limb dependency are not mediated by a sympathetic mechanism in humans. Acta Physiol (Oxf) 2012; 205:372-80. [PMID: 22276905 DOI: 10.1111/j.1748-1716.2012.02416.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2011] [Revised: 11/30/2011] [Accepted: 01/16/2012] [Indexed: 11/30/2022]
Abstract
AIMS We tested the hypotheses that vasoconstrictor responses to limb dependency are: (i) greater in the leg than the arm, (ii) impaired with age and (iii) not sympathetically mediated. METHODS Vascular responses to limb dependency (i.e. lowering the limb from heart level to 30 cm below heart level) were determined in 17 young and 17 older adults. Indices of blood flow were obtained in the brachial and popliteal arteries (Doppler ultrasound) as well as in the cutaneous circulation (forearm and calf using laser-Doppler flowmetry). Vasoconstriction was quantified by calculating the indices of vascular resistance as height corrected mean arterial pressure/limb blood velocity or skin flux. A second group of subjects repeated the limb dependency trials after acute systemic sympathetic blockade. RESULTS Limb dependency increased vascular resistance index in the brachial artery (∆59 ± 8%; P<0.05) and popliteal artery (∆99 ± 10%; P<0.05 for change in heart level and brachial vs. popliteal) of young and older adults (∆60 + 9% brachial and ∆61 ± 7% popliteal arteries; P<0.05 for change in heart level and response in popliteal young vs. older adults). In contrast, cutaneous vasoconstrictor responses to limb dependency were similar in the forearm (∆218 ± 29% and ∆200 ± 29% for young and older adults, respectively) and calf (∆257 ± 32% and ∆236 ± 29%; all P<0.05 from heart level) of young and older adults. Vasoconstrictor responses to limb dependency were not affected by sympathetic blockade in young or older adults. CONCLUSION These findings indicate that age-, limb-, and tissue-related differences may exist in the vasoconstrictor response to limb dependency in healthy humans, which are not sympathetically mediated.
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Affiliation(s)
- K. A. M. Snyder
- Penn State Heart and Vascular Institute; Pennsylvania State University College of Medicine; Hershey; PA; USA
| | - S. Shamimi-Noori
- Penn State Heart and Vascular Institute; Pennsylvania State University College of Medicine; Hershey; PA; USA
| | - T. E. Wilson
- Departments of Biomedical Sciences & of Specialty Medicine; Ohio University Heritage College of Osteopathic Medicine; Athens; OH; USA
| | - K. D. Monahan
- Penn State Heart and Vascular Institute; Pennsylvania State University College of Medicine; Hershey; PA; USA
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Inskip JA, Ramer LM, Ramer MS, Krassioukov AV, Claydon VE. Spectral analyses of cardiovascular control in rodents with spinal cord injury. J Neurotrauma 2012; 29:1638-49. [PMID: 22260380 DOI: 10.1089/neu.2011.2145] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The severity of injury to cardiovascular autonomic pathways following clinical spinal cord injury (SCI) can be evaluated with spectral analyses. Whether this technique provides a translatable assessment of cardiovascular autonomic function in rodent SCI is unknown. Beat-to-beat blood pressure and pulse interval were measured in male rats 1 month after complete T3 or T10 SCI, and in uninjured control animals. Univariate autoregressive spectral analyses were performed and the power of the low frequency (LF), high frequency (HF), and very low frequency (VLF) peaks identified. Frequency domain variables were correlated with the severity of orthostatic hypotension (OH) and the severity of hypertension during autonomic dysreflexia (AD). Total heart rate variability (HRV) and blood pressure variability (BPV) were reduced in animals with T3, but not T10, SCI. VLF and LF HRV were reduced and HF HRV was increased in animals with T3 SCI compared to controls; there were no changes in animals with T10 SCI. BPV in the VLF and LF range was reduced in animals with T3 SCI, but not T10 SCI. In all animals with SCI, severity of OH was positively correlated with LF BPV, and negatively correlated with HF BPV. Severity of AD was positively correlated with HF BPV and HF HRV, and negatively correlated with VLF HRV. Spectral analyses can detect alterations in cardiovascular autonomic function in animals with SCI at rest. These parameters underscore the distinct cardiovascular ramifications of high- versus low-thoracic SCI, and correlate with the severity of AD and OH, clinically-relevant measures of abnormal blood pressure control.
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Affiliation(s)
- Jessica A Inskip
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada
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Shilo M, Gefen A. Identification of capillary blood pressure levels at which capillary collapse is likely in a tissue subjected to large compressive and shear deformations. Comput Methods Biomech Biomed Engin 2011; 15:59-71. [PMID: 21181574 DOI: 10.1080/10255842.2010.539208] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Pressure ulcers (PU) are localised damage to skin and underlying tissues, caused by sustained tissue deformations and ischaemia. PU typically appear in insensitive or immobile patients, e.g. those with spinal cord injury (SCI) or geriatric patients. As these patients often experience fluctuations in blood pressure, and are also exposed to high-shear loads in their weight-bearing soft tissues during wheelchair sitting or bed rest, we used an inverse finite element method to determine the effects of capillary blood pressure (CBP) and shear deformations on occurrence of mechanical collapse in capillaries. We studied collapse in straight, U-shaped and bifurcated capillaries. All model configurations were consistent in demonstrating that the level of CBP has a considerable influence on the likelihood of capillary collapse in the physiological CBP range, particularly if shear is present. Our modelling therefore suggests that low CBP is a 'suspect' risk factor for PU in SCI and geriatric patients.
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Affiliation(s)
- Malka Shilo
- Department of Biomedical Engineering, Faculty of Engineering, Tel Aviv University, Tel Aviv, 69978, Israel
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Groothuis JT, Thijssen DHJ, Lenders JWM, Deinum J, Hopman MTE. Leg vasoconstriction during head-up tilt in patients with autonomic failure is not abolished. J Appl Physiol (1985) 2011; 110:416-22. [PMID: 21127209 DOI: 10.1152/japplphysiol.01098.2010] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Maintaining blood pressure during orthostatic challenges is primarily achieved by baroreceptor-mediated activation of the sympathetic nervous system, which can be divided into preganglionic and postganglionic parts. Despite their preganglionic autonomic failure, spinal cord-injured individuals demonstrate a preserved peripheral vasoconstriction during orthostatic challenges. Whether this also applies to patients with postganglionic autonomic failure is unknown. Therefore, we assessed leg vasoconstriction during 60° head-up tilt in five patients with pure autonomic failure (PAF) and two patients with autonomic failure due to dopamine-β-hydroxylase (DBH) deficiency. Ten healthy subjects served as controls. Leg blood flow was measured using duplex ultrasound in the right superficial femoral artery. Leg vascular resistance was calculated as the arterial-venous pressure gradient divided by blood flow. DBH-deficient patients were tested off and on the norepinephrine pro-drug l-threo-dihydroxyphenylserine (l-DOPS). During 60° head-up tilt, leg vascular resistance increased significantly in PAF patients [0.40 ± 0.38 (+30%) mmHg·ml−1·min−1]. The increase in leg vascular resistance was not significantly different from controls [0.88 ± 1.04 (+72%) mmHg·ml−1·min−1]. In DBH-deficient patients, leg vascular resistance increased by 0.49 ± 0.01 (+153%) and 1.52 ± 1.47 (+234%) mmHg·ml−1·min−1 off and on l-DOPS, respectively. Despite the increase in leg vascular resistance, orthostatic hypotension was present in PAF and DBH-deficient patients. Our results demonstrate that leg vasoconstriction during orthostatic challenges in patients with PAF or DBH deficiency is not abolished. This indicates that the sympathetic nervous system is not the sole or pivotal mechanism inducing leg vasoconstriction during orthostatic challenges. Additional vasoconstrictor mechanisms may compensate for the loss in sympathetic nervous system control.
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Affiliation(s)
- Jan T. Groothuis
- Departments of 1Physiology and
- Department of Rehabilitation, Sint Maartenskliniek, Nijmegen, The Netherlands
| | - Dick H. J. Thijssen
- Departments of 1Physiology and
- Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, United Kingdom; and
| | - Jacques W. M. Lenders
- Internal Medicine, Radboud University Nijmegen Medical Centre, Nijmegen
- Department of Medicine III, Carl Gustav Carus University Medical Center, Dresden, Germany
| | - Jaap Deinum
- Internal Medicine, Radboud University Nijmegen Medical Centre, Nijmegen
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Abstract
To examine the role of limb posture on vascular conductance during rapid changes in vascular transmural pressure, we determined brachial (n = 10) and femoral (n = 10) artery post-occlusive reactive hyperemic blood flow (RHBF, ultrasound/Doppler) and vascular conductance in healthy humans with each limb at three different positions-horizontal, up and down. Limb posture was varied by raising or lowering the arm or leg from the horizontal position by 45°. In both limbs, peak RHBF and vascular conductance were highest in the down or horizontal position and lowest in the up position (arm up 338 ± 38, supine 430 ± 52, down 415 ± 52 ml/min, P < 0.05; leg up 1,208 ± 88, supine 1,579 ± 130, down 1,767 ± 149 ml/min, P < 0.05). In contrast, the maximal dynamic fall in blood flow following peak RHBF (in ml/s/s) in both limbs was highest in the limb-down position and lowest with the limb elevated (P < 0.05). These data suggest that the magnitude and temporal pattern of limb reactive hyperemia is in part related to changes in vascular transmural pressure and independent of systemic blood pressure and sympathetic control.
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La Fountaine MF, Radulovic M, Cardozo CP, Spungen AM, DeMeersman RE, Bauman WA. Effects of acute nitric oxide synthase inhibition on lower leg vascular function in chronic tetraplegia. J Spinal Cord Med 2009; 32:538-44. [PMID: 20025149 PMCID: PMC2792459 DOI: 10.1080/10790268.2009.11754555] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
BACKGROUND/OBJECTIVE To improve our understanding of the lower-leg vascular responses of nitric oxide synthase inhibition in persons with tetraplegia. PARTICIPANTS Six people with chronic tetraplegia and 6 age-matched controls. METHODS Lower-leg relative vascular resistance and venous volume variation were obtained by venous occlusion plethysmography and blood pressure by auscultation at baseline. Postintravenous infusion of the nitric oxide synthase inhibitor NG-nitro-L-arginine-methyl-ester (1 mg x kg(-1) or placebo on separate days. RESULTS At baseline in the group with tetraplegia compared with controls, mean arterial pressure and relative vascular resistance of the leg were significantly lower. After nitric oxide synthase inhibition, mean arterial pressure and lower leg vascular resistance were significantly elevated in both groups. There were no group or intervention differences in venous volume variation. CONCLUSION These preliminary results suggest that nitric oxide synthase inhibition with 1 mg x kg(-1) N(G)-nitro-L-arginine-methyl-ester normalizes seated blood pressure and lower leg vascular resistance to control group baseline levels.
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Affiliation(s)
- Michael F La Fountaine
- VA Center of Excellence on the Medical Consequences of Spinal Cord Injury, James J. Peters VA Medical Center, SCI Room 1E-02, 130 W. Kingsbridge Road, Bronx, NY 10468, USA.
| | - Miroslav Radulovic
- VA Center of Excellence on the Medical Consequences of Spinal Cord Injury, James J. Peters VA Medical Center, Bronx, New York
| | - Christopher P Cardozo
- VA Center of Excellence on the Medical Consequences of Spinal Cord Injury, James J. Peters VA Medical Center, Bronx, New York
| | - Ann M Spungen
- VA Center of Excellence on the Medical Consequences of Spinal Cord Injury, James J. Peters VA Medical Center, Bronx, New York
| | - Ronald E DeMeersman
- Department of Biobehavioral Sciences, Teachers College, Columbia University, New York, New York
| | - William A Bauman
- VA Center of Excellence on the Medical Consequences of Spinal Cord Injury, James J. Peters VA Medical Center, Bronx, New York
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Groothuis JT, Poelkens F, Wouters CW, Kooijman M, Hopman MTE. Leg intravenous pressure during head-up tilt. J Appl Physiol (1985) 2008; 105:811-5. [PMID: 18635882 DOI: 10.1152/japplphysiol.90304.2008] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Leg vascular resistance is calculated as the arterial-venous pressure gradient divided by blood flow. During orthostatic challenges it is assumed that the hydrostatic pressure contributes equally to leg arterial, as well as to leg venous pressure. Because of venous valves, one may question whether, during orthostatic challenges, a continuous hydrostatic column is formed and if leg venous pressure is equal to the hydrostatic pressure. The purpose of this study was, therefore, to measure intravenous pressure in the great saphenous vein of 12 healthy individuals during 30 degrees and 70 degrees head-up tilt and compare this with the calculated hydrostatic pressure. The height difference between the heart and the right medial malleolus level represented the hydrostatic column. The results demonstrate that there were no differences between the measured intravenous pressure and the calculated hydrostatic pressure during 30 degrees (47.2 +/- 1.0 and 46.9 +/- 1.5 mmHg, respectively) and 70 degrees head-up tilt (83.9 +/- 0.9 and 85.1 +/- 1.2 mmHg, respectively). Steady-state levels of intravenous pressure were reached after 95 +/- 12 s during 30 degrees and 161 +/- 15 s during 70 degrees head-up tilt. In conclusion, the measured leg venous pressure is similar to the calculated hydrostatic pressure during orthostatic challenges. Therefore, the assumption that hydrostatic pressure contributes equally to leg arterial as well as to leg venous pressure during orthostatic challenges can be made.
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Affiliation(s)
- Jan T Groothuis
- Radboud Univ. Nijmegen Medical Centre, Dept. of Physiology, Geert Grooteplein-noord 21, 6525 EZ Nijmegen, The Netherlands
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