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[PMID]:28818141
[Au] Autor:Zhang Q; Evans JM; Stenger MB; Moore FB; Knapp CF
[Ti] Título:Autonomic Cardiovascular Responses to Orthostatic Stress After a Short Artificial Gravity Exposure.
[So] Source:Aerosp Med Hum Perform;88(9):827-833, 2017 Sep 01.
[Is] ISSN:2375-6314
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:BACKGROUND: Intermittent artificial gravity (AG) training over days and weeks has been shown to improve the human orthostatic tolerance limit (OTL) and improve cardiovascular regulation in response to orthostatic stress. Effects of a single AG exposure are currently unknown. METHODS: We tested cardiovascular responses to orthostatic stress in 16 hypovolemic subjects (9 men and 7 women), once following a single, short (∼90 min) bout of AG and once following a similar period of head-down bed rest (HDBR). Hypovolemia was produced by intravenous furosemide infusion (20 mg) and orthostatic stress was produced by combined 70° head-up tilt (HUT) and progressively increasing lower body negative pressure until symptoms of presyncope developed. To assess reflex-induced changes in cardiovascular regulation, heart rate and blood pressure variability were analyzed by spectral analysis and baroreflex activity was evaluated by transfer function analysis. RESULTS: Compared to HDBR, a short AG exposure increased men's low frequency (0.04-0.15 Hz) power of systolic blood pressure (SBPLF), but did not change women's SBPLF responses to orthostatic stress. In response to 70° HUT, compared to supine, low frequency phase delay (PhaseLF) between systolic blood pressure and RR intervals increased by ∼20% following HDBR, but did not change following AG, reflecting improved baroreflex activity at a milder level of orthostatic stress after AG. CONCLUSIONS: These results indicate that a short bout of AG increased both sympathetic and baroreflex responsiveness to orthostatic stress in hypovolemia-induced, cardiovascular-deconditioned men and women, which may contribute to the AG-induced improvement of OTL shown in our previous reports.Zhang Q, Evans JM, Stenger MB, Moore FB, Knapp CF. Autonomic cardiovascular responses to orthostatic stress after a short artificial gravity exposure. Aerosp Med Hum Perform. 2017; 88(9):827-833.
[Mh] Termos MeSH primário: Sistema Nervoso Autônomo/fisiologia
Descondicionamento Cardiovascular/fisiologia
Gravidade Alterada
Decúbito Inclinado com Rebaixamento da Cabeça/fisiologia
[Mh] Termos MeSH secundário: Adulto
Barorreflexo/fisiologia
Repouso em Cama
Pressão Sanguínea/fisiologia
Feminino
Frequência Cardíaca/fisiologia
Hemodinâmica/fisiologia
Seres Humanos
Hipovolemia/fisiopatologia
Pressão Negativa da Região Corporal Inferior
Masculino
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Em] Mês de entrada:1710
[Cu] Atualização por classe:171010
[Lr] Data última revisão:
171010
[Sb] Subgrupo de revista:IM; S
[Da] Data de entrada para processamento:170819
[St] Status:MEDLINE
[do] DOI:10.3357/AMHP.4811.2017


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[PMID]:28501796
[Au] Autor:Stewart JM; Sutton R; Kothari ML; Goetz AM; Visintainer P; Medow MS
[Ad] Endereço:Departments of Pediatrics, New York Medical College, Valhalla, New York, USA.
[Ti] Título:Nitric oxide synthase inhibition restores orthostatic tolerance in young vasovagal syncope patients.
[So] Source:Heart;103(21):1711-1718, 2017 Nov.
[Is] ISSN:1468-201X
[Cp] País de publicação:England
[La] Idioma:eng
[Ab] Resumo:OBJECTIVE: Syncope is sudden transient loss of consciousness and postural tone with spontaneous recovery; the most common form is vasovagal syncope (VVS). We previously demonstrated impaired post-synaptic adrenergic responsiveness in young VVS patients was reversed by blocking nitric oxide synthase (NOS). We hypothesised that nitric oxide may account for reduced orthostatic tolerance in young recurrent VVS patients. METHODS: We recorded haemodynamics in supine VVS and healthy volunteers (aged 15-27 years), challenged with graded lower body negative pressure (LBNP) (-15, -30, -45 mm Hg each for 5 min, then -60 mm Hg for a maximum of 50 min) with and without NOS inhibitor N -monomethyl-L-arginine acetate (L-NMMA). Saline plus phenylephrine (Saline+PE) was used as volume and pressor control for L-NMMA. RESULTS: Controls endured 25.9±4.0 min of LBNP during Saline+PE compared with 11.6±1.4 min for fainters (p<0.001). After L-NMMA, control subjects endured 24.8±3.2 min compared with 22.6±1.6 min for fainters. Mean arterial pressure decreased more in VVS patients during LBNP with Saline+PE (p<0.001) which was reversed by L-NMMA; cardiac output decreased similarly in controls and VVS patients and was unaffected by L-NMMA. Total peripheral resistance increased for controls but decreased for VVS during Saline+PE (p<0.001) but was similar following L-NMMA. Splanchnic vascular resistance increased during LBNP in controls, but decreased in VVS patients following Saline+PE which L-NMMA restored. CONCLUSIONS: We conclude that arterial vasoconstriction is impaired in young VVS patients, which is corrected by NOS inhibition. The data suggest that both pre- and post-synaptic arterial vasoconstriction may be affected by nitric oxide.
[Mh] Termos MeSH primário: Artérias/efeitos dos fármacos
Inibidores Enzimáticos/administração & dosagem
Hemodinâmica/efeitos dos fármacos
Óxido Nítrico Sintase/antagonistas & inibidores
Síncope Vasovagal/tratamento farmacológico
ômega-N-Metilarginina/administração & dosagem
[Mh] Termos MeSH secundário: Administração Intravenosa
Adolescente
Adulto
Fatores Etários
Pressão Arterial/efeitos dos fármacos
Artérias/enzimologia
Artérias/fisiopatologia
Débito Cardíaco/efeitos dos fármacos
Feminino
Seres Humanos
Pressão Negativa da Região Corporal Inferior
Masculino
Óxido Nítrico Sintase/metabolismo
Síncope Vasovagal/diagnóstico
Síncope Vasovagal/enzimologia
Síncope Vasovagal/fisiopatologia
Fatores de Tempo
Resultado do Tratamento
Resistência Vascular/efeitos dos fármacos
Vasoconstrição/efeitos dos fármacos
Adulto Jovem
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Nm] Nome de substância:
0 (Enzyme Inhibitors); 27JT06E6GR (omega-N-Methylarginine); EC 1.14.13.39 (Nitric Oxide Synthase)
[Em] Mês de entrada:1710
[Cu] Atualização por classe:171024
[Lr] Data última revisão:
171024
[Sb] Subgrupo de revista:AIM; IM
[Da] Data de entrada para processamento:170515
[St] Status:MEDLINE
[do] DOI:10.1136/heartjnl-2017-311161


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[PMID]:28258058
[Au] Autor:Sugawara J; Tomoto T; Imai T; Maeda S; Ogoh S
[Ad] Endereço:Human Informatics Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan; jun.sugawara@aist.go.jp.
[Ti] Título:Impact of mild orthostatic stress on aortic-cerebral hemodynamic transmission: insight from the frequency domain.
[So] Source:Am J Physiol Heart Circ Physiol;312(5):H1076-H1084, 2017 May 01.
[Is] ISSN:1522-1539
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:High cerebral pressure and flow fluctuations could be a risk for future cerebrovascular disease. This study aims to determine whether acute systemic vasoconstriction affects the dynamic pulsatile hemodynamic transmission from the aorta to the brain. We applied a stepwise lower body negative pressure (LBNP) (-10, -20, and -30 mmHg) in 15 young men to induce systemic vasoconstriction. To elucidate the dynamic relationship between the changes in aortic pressure (AoP; estimated from the radial arterial pressure waveforms) and the cerebral blood flow velocity (CBFV) at the middle cerebral artery (via a transcranial Doppler), frequency-domain analysis characterized the beat-to-beat slow oscillation (0.02-0.30 Hz) and the intra-beat rapid change (0.78-9.69 Hz). The systemic vascular resistance gradually and significantly increased throughout the LBNP protocol. In the low-frequency range (LF: 0.07-0.20 Hz) of a slow oscillation, the normalized transfer function gain of the steady-state component (between mean AoP and mean CBFV) remained unchanged, whereas that of the pulsatile component (between pulsatile AoP and pulsatile CBFV) was significantly augmented during -20 and -30 mmHg of LBNP (+28.8% and +32.4% vs. baseline). Furthermore, the relative change in the normalized transfer function gain of the pulsatile component at the LF range correlated with the corresponding change in systemic vascular resistance ( = 0.41, = 0.005). Regarding the intra-beat analysis, the normalized transfer function gain from AoP to CBFV was not significantly affected by the LBNP stimulation ( = 0.77). Our findings suggest that systemic vasoconstriction deteriorates the dampening effect on the pulsatile hemodynamics toward the brain, particularly in slow oscillations (e.g., 0.07-0.20 Hz). We characterized the pulsatile hemodynamic transmission from the heart to the brain by frequency-domain analysis. The low-frequency transmission was augmented with a mild LBNP stimulation partly due to the elevated systemic vascular resistance. A systemic vasoconstriction deteriorates the dampening effect on slow oscillations of pulsatile hemodynamics toward the brain.
[Mh] Termos MeSH primário: Aorta/fisiologia
Pressão Arterial/fisiologia
Velocidade do Fluxo Sanguíneo/fisiologia
Circulação Cerebrovascular/fisiologia
Pressão Negativa da Região Corporal Inferior/métodos
Fluxo Pulsátil/fisiologia
[Mh] Termos MeSH secundário: Adulto
Relógios Biológicos/fisiologia
Seres Humanos
Masculino
Oscilometria/métodos
Resistência Vascular/fisiologia
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Em] Mês de entrada:1708
[Cu] Atualização por classe:170821
[Lr] Data última revisão:
170821
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:170305
[St] Status:MEDLINE
[do] DOI:10.1152/ajpheart.00802.2016


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[PMID]:28159806
[Au] Autor:Merchant S; Medow MS; Visintainer P; Terilli C; Stewart JM
[Ad] Endereço:Department of Pediatrics, New York Medical College, Valhalla, New York.
[Ti] Título:Oscillatory lower body negative pressure impairs working memory task-related functional hyperemia in healthy volunteers.
[So] Source:Am J Physiol Heart Circ Physiol;312(4):H672-H680, 2017 Apr 01.
[Is] ISSN:1522-1539
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:Neurovascular coupling (NVC) describes the link between an increase in task-related neural activity and increased cerebral blood flow denoted "functional hyperemia." We previously showed induced cerebral blood flow oscillations suppressed functional hyperemia; conversely functional hyperemia also suppressed cerebral blood flow oscillations. We used lower body negative pressure (OLBNP) oscillations to force oscillations in middle cerebral artery cerebral blood flow velocity (CBFv). Here, we used N-back testing, an intellectual memory challenge as a neural activation task, to test the hypothesis that OLBNP-induced oscillatory cerebral blood flow can reduce functional hyperemia and NVC produced by a working memory task and can interfere with working memory. We used OLBNP (-30 mmHg) at 0.03, 0.05, and 0.10 Hz and measured spectral power of CBFv at all frequencies. Neither OLBNP nor N-back, alone or combined, affected hemodynamic parameters. 2-Back power and OLBNP individually were compared with 2-back power during OLBNP. 2-Back alone produced a narrow band increase in oscillatory arterial pressure (OAP) and oscillatory cerebral blood flow power centered at 0.0083 Hz. Functional hyperemia in response to 2-back was reduced to near baseline and 2-back memory performance was decreased by 0.03-, 0.05-, and 0.10-Hz OLBNP. OLBNP alone produced increased oscillatory power at frequencies of oscillation not suppressed by added 2-back. However, 2-back preceding OLBNP suppressed OLBNP power. OLBNP-driven oscillatory CBFv blunts NVC and memory performance, while memory task reciprocally interfered with forced CBFv oscillations. This shows that induced cerebral blood flow oscillations suppress functional hyperemia and functional hyperemia suppresses cerebral blood flow oscillations. We show that induced cerebral blood flow oscillations suppress functional hyperemia produced by a working memory task as well as memory task performance. We conclude that oscillatory cerebral blood flow produces causal reductions of memory task neurovascular coupling and memory task performance. Reductions of functional hyperemia are constrained by autoregulation.
[Mh] Termos MeSH primário: Hiperemia/fisiopatologia
Hiperemia/psicologia
Pressão Negativa da Região Corporal Inferior/psicologia
Transtornos da Memória/psicologia
Memória de Curto Prazo
[Mh] Termos MeSH secundário: Adulto
Pressão Arterial
Circulação Cerebrovascular
Feminino
Voluntários Saudáveis
Hemodinâmica
Seres Humanos
Hiperemia/diagnóstico por imagem
Masculino
Transtornos da Memória/etiologia
Artéria Cerebral Média/fisiopatologia
Desempenho Psicomotor
Ultrassonografia Doppler Transcraniana
Adulto Jovem
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Em] Mês de entrada:1707
[Cu] Atualização por classe:170728
[Lr] Data última revisão:
170728
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:170205
[St] Status:MEDLINE
[do] DOI:10.1152/ajpheart.00438.2016


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[PMID]:28104979
[Au] Autor:Rodrigues FG; Dasilva G; Wexner SD
[Ad] Endereço:Fabio G Rodrigues, Giovanna Dasilva, Steven D Wexner, Department of Colorectal Surgery, Cleveland Clinic Florida, Weston, FL 33331, United States.
[Ti] Título:Neutropenic enterocolitis.
[So] Source:World J Gastroenterol;23(1):42-47, 2017 Jan 07.
[Is] ISSN:2219-2840
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:Neutropenic colitis is a severe condition usually affecting immunocompromised patients. Its exact pathogenesis is not completely understood. The main elements in disease onset appear to be intestinal mucosal injury together with neutropenia and the weakened immune system of the afflicted patients. These initial conditions lead to intestinal edema, engorged vessels, and a disrupted mucosal surface, which becomes more vulnerable to bacterial intramural invasion. Chemotherapeutic agents can cause direct mucosal injury (mucositis) or can predispose to distension and necrosis, thereby altering intestinal motility. This article aims to review current concepts regarding neutropenic colitis' pathogenesis, diagnosis, and management.
[Mh] Termos MeSH primário: Enterocolite Neutropênica/diagnóstico
Enterocolite Neutropênica/etiologia
Enterocolite Neutropênica/terapia
Neutropenia/complicações
Tiflite/diagnóstico
Tiflite/etiologia
Tiflite/terapia
[Mh] Termos MeSH secundário: Antibacterianos/uso terapêutico
Antineoplásicos/efeitos adversos
Antineoplásicos/uso terapêutico
Colectomia
Terapia Combinada
Hidratação
Seres Humanos
Transfusão de Leucócitos
Pressão Negativa da Região Corporal Inferior
Neoplasias/tratamento farmacológico
Neutropenia/induzido quimicamente
Nutrição Parenteral
[Pt] Tipo de publicação:JOURNAL ARTICLE; REVIEW
[Nm] Nome de substância:
0 (Anti-Bacterial Agents); 0 (Antineoplastic Agents)
[Em] Mês de entrada:1707
[Cu] Atualização por classe:170717
[Lr] Data última revisão:
170717
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:170121
[St] Status:MEDLINE
[do] DOI:10.3748/wjg.v23.i1.42


  6 / 1259 MEDLINE  
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[PMID]:28095958
[Au] Autor:Ishibashi K; Oyama F; Yoshida H; Iwanaga K
[Ti] Título:Additive Effects of Sinusoidal Lower Body Negative Pressure on Cardiovascular Responses.
[So] Source:Aerosp Med Hum Perform;88(2):137-141, 2017 Feb 01.
[Is] ISSN:2375-6314
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:BACKGROUND: Sinusoidal lower body negative pressure (SLBNP) has been used to investigate the cardiovascular response to slow periodic changes in blood shifts, but measurements of slow fluctuations take a long time if measured for each period of SLBNP separately. Our study aimed to investigate whether the cardiovascular responses to superimposed SLBNP (S-SLBNP), which is expected to reduce the measurement time, are different from responses measured individually. METHODS: S-SLBNP was configured by superimposing two conventional SLBNPs (C-SLBNP) at 180-s and 30-s periods in the pressure range from 0 to -25 mmHg. As the S-SLBNP has double the static load of C-SLBNP, we also used offset SLBNP (O-SLBNP), which has the same static load level as S-SLBNP. Heart rate (HR), thoracic impedance (Z0), and mean arterial pressure (MAP) were measured from 11 male subjects. The transfer functions of gains from MAP to HR (Gain-HR/MAP) and from Z0 to HR (Gain-HR/Z0) were calculated as indexes of arterial baroreflex and cardiopulmonary baroreflex regulation of HR, respectively. RESULTS: The Gain-HR/MAP in the 180-s period (2.11 ± 0.17 bpm/mmHg; mean ± SEM) was larger than that of the 30-s period (1.04 ± 0.09 bpm/mmHg); however, there was no significant difference between the SLBNP conditions. The Gain-HR/Z0 in C-SLBNP (9.37 ± 1.47 bpm/ohm) was smaller than that of the other conditions [18.46 ± 2.45 bpm/ohm (O-SLBNP); 16.09 ± 2.29 bpm/ohm (S-SLBNP)]. DISCUSSION: Using S-SLBNP could reduce the measurement time needed to examine the arterial baroreflex. However, the cardiopulmonary baroreflex was modified by the static load of SLBNP.Ishibashi K, Oyama F, Yoshida H, Iwanaga K. Additive effects of sinusoidal lower body negative pressure on cardiovascular responses. Aerosp Med Hum Perform. 2017; 88(2):137-141.
[Mh] Termos MeSH primário: Pressão Arterial
Barorreflexo
Frequência Cardíaca
Pressão Negativa da Região Corporal Inferior
[Mh] Termos MeSH secundário: Pressão Sanguínea
Cardiografia de Impedância
Voluntários Saudáveis
Seres Humanos
Masculino
Fatores de Tempo
Adulto Jovem
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Em] Mês de entrada:1703
[Cu] Atualização por classe:170309
[Lr] Data última revisão:
170309
[Sb] Subgrupo de revista:IM; S
[Da] Data de entrada para processamento:170119
[St] Status:MEDLINE
[do] DOI:10.3357/AMHP.4720.2017


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[PMID]:28061916
[Au] Autor:Marshall-Goebel K; Mulder E; Bershad E; Laing C; Eklund A; Malm J; Stern C; Rittweger J
[Ti] Título:Intracranial and Intraocular Pressure During Various Degrees of Head-Down Tilt.
[So] Source:Aerosp Med Hum Perform;88(1):10-16, 2017 Jan 01.
[Is] ISSN:2375-6314
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:BACKGROUND: More than half of astronauts develop ophthalmic changes during long-duration spaceflight consistent with an abnormal intraocular and intracranial pressure (IOP, ICP) difference. The aim of our study was to assess IOP and ICP during head-down tilt (HDT) and the additive or attenuating effects of 1% CO2 and lower body negative pressure (LBNP). METHODS: In Experiment I, IOP and ICP were measured in nine healthy subjects after 3.5 h HDT in five conditions: -6°, -12°, and -18° HDT, -12° with 1% CO2, and -12° with -20 mmHg LBNP. In Experiment II, IOP was measured in 16 healthy subjects after 5 min tilt at +12°, 0°, -6°, -12°, -18°, and -24°, with and without -40 mmHg LBNP. RESULTS: ICP was only found to increase from supine baseline during -18° HDT (9.2 ± 0.9 and 14.4 ± 1 mmHg, respectively), whereas IOP increased from 15.7 ± 0.3 mmHg at 0° to 17.9 ± 0.4 mmHg during -12° HDT and from 15.3 ± 0.4 mmHg at 0° to 18.7 ± 0.4 mmHg during -18° HDT. The addition of -20 mmHg LBNP or 1% CO2 had no further effects on ICP or IOP. However, the use of -40 mmHg LBNP during HDT lowered IOP back to baseline values, except at -24° HDT. DISCUSSION: A small, posterior intraocular-intracranial pressure difference (IOP > ICP) is maintained during HDT, and a sustained or further decreased difference may lead to structural changes in the eye in real and simulated microgravity.Marshall-Goebel K, Mulder E, Bershad E, Laing C, Eklund A, Malm J, Stern C, Rittweger J. Intracranial and intraocular pressure during various degrees of head-down tilt. Aerosp Med Hum Perform. 2017; 88(1):10-16.
[Mh] Termos MeSH primário: Decúbito Inclinado com Rebaixamento da Cabeça/fisiologia
Pressão Intracraniana/fisiologia
Pressão Intraocular/fisiologia
[Mh] Termos MeSH secundário: Adulto
Dióxido de Carbono
Decúbito Inclinado com Rebaixamento da Cabeça/efeitos adversos
Voluntários Saudáveis
Seres Humanos
Pressão Negativa da Região Corporal Inferior/efeitos adversos
Masculino
Postura
Voo Espacial
Ultrassonografia Doppler Transcraniana
Transtornos da Visão/etiologia
Simulação de Ausência de Peso
Adulto Jovem
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Nm] Nome de substância:
142M471B3J (Carbon Dioxide)
[Em] Mês de entrada:1702
[Cu] Atualização por classe:170221
[Lr] Data última revisão:
170221
[Sb] Subgrupo de revista:IM; S
[Da] Data de entrada para processamento:170108
[St] Status:MEDLINE
[do] DOI:10.3357/AMHP.4653.2017


  8 / 1259 MEDLINE  
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[PMID]:27911370
[Au] Autor:Convertino VA; Hinojosa-Laborde C; Muniz GW; Carter R
[Ad] Endereço:U.S. Army Institute of Surgical Research, JBSA Fort Sam Houston; U.S. Army Medical Research and Materiel Command, JBSA Fort Sam Houston; victor.a.convertino.civ@mail.mil.
[Ti] Título:Integrated Compensatory Responses in a Human Model of Hemorrhage.
[So] Source:J Vis Exp;(117), 2016 Nov 20.
[Is] ISSN:1940-087X
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:Hemorrhage is the leading cause of trauma-related deaths, partly because early diagnosis of the severity of blood loss is difficult. Assessment of hemorrhaging patients is difficult because current clinical tools provide measures of vital signs that remain stable during the early stages of bleeding due to compensatory mechanisms. Consequently, there is a need to understand and measure the total integration of mechanisms that compensate for reduced circulating blood volume and how they change during ongoing progressive hemorrhage. The body's reserve to compensate for reduced circulating blood volume is called the 'compensatory reserve'. The compensatory reserve can be accurately evaluated with real-time measurements of changes in the features of the arterial waveform measured with the use of a high-powered computer. Lower Body Negative Pressure (LBNP) has been shown to simulate many of the physiological responses in humans associated with hemorrhage, and is used to study the compensatory response to hemorrhage. The purpose of this study is to demonstrate how compensatory reserve is assessed during progressive reductions in central blood volume with LBNP as a simulation of hemorrhage.
[Mh] Termos MeSH primário: Hemorragia
Modelos Teóricos
[Mh] Termos MeSH secundário: Pressão Sanguínea
Volume Sanguíneo
Frequência Cardíaca
Seres Humanos
Pressão Negativa da Região Corporal Inferior
[Pt] Tipo de publicação:JOURNAL ARTICLE; VIDEO-AUDIO MEDIA
[Em] Mês de entrada:1709
[Cu] Atualização por classe:170911
[Lr] Data última revisão:
170911
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:161203
[St] Status:MEDLINE
[do] DOI:10.3791/54737


  9 / 1259 MEDLINE  
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[PMID]:27733385
[Au] Autor:Usselman CW; Nielson CA; Luchyshyn TA; Gimon TI; Coverdale NS; Van Uum SH; Shoemaker JK
[Ad] Endereço:Neurovascular Research Laboratory, School of Kinesiology, Western University, London, Ontario, Canada.
[Ti] Título:Hormone phase influences sympathetic responses to high levels of lower body negative pressure in young healthy women.
[So] Source:Am J Physiol Regul Integr Comp Physiol;311(5):R957-R963, 2016 Nov 01.
[Is] ISSN:1522-1490
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:We tested the hypothesis that sympathetic responses to baroreceptor unloading may be affected by circulating sex hormones. During lower body negative pressure at -30, -60, and -80 mmHg, muscle sympathetic nerve activity (MSNA), heart rate, and blood pressure were recorded in women who were taking (n = 8) or not taking (n = 9) hormonal contraceptives. All women were tested twice, once during the low-hormone phase (i.e., the early follicular phase of the menstrual cycle and the placebo phase of hormonal contraceptive use), and again during the high-hormone phase (i.e., the midluteal phase of the menstrual cycle and active phase of contraceptive use). During baroreceptor unloading, the reductions in stroke volume and resultant increases in MSNA and total peripheral resistance were greater in high-hormone than low-hormone phases in both groups. When normalized to the fall in stroke volume, increases in MSNA were no longer different between hormone phases. While stroke volume and sympathetic responses were similar between women taking and not taking hormonal contraceptives, mean arterial pressure was maintained during baroreceptor unloading in women not taking hormonal contraceptives but not in women using hormonal contraceptives. These data suggest that differences in sympathetic activation between hormone phases, as elicited by lower body negative pressure, are the result of hormonally mediated changes in the hemodynamic consequences of negative pressure, rather than centrally driven alterations to sympathetic regulation.
[Mh] Termos MeSH primário: Pressão Sanguínea/fisiologia
Hormônios Esteroides Gonadais/sangue
Frequência Cardíaca/fisiologia
Pressão Negativa da Região Corporal Inferior
Pressorreceptores/fisiologia
Sistema Nervoso Simpático/fisiologia
[Mh] Termos MeSH secundário: Adulto
Pressão Sanguínea/efeitos dos fármacos
Anticoncepcionais Orais Hormonais/administração & dosagem
Anticoncepcionais Orais Hormonais/farmacologia
Feminino
Fase Folicular/efeitos dos fármacos
Fase Folicular/fisiologia
Frequência Cardíaca/efeitos dos fármacos
Seres Humanos
Fase Luteal/efeitos dos fármacos
Fase Luteal/fisiologia
Pressorreceptores/efeitos dos fármacos
Sistema Nervoso Simpático/diagnóstico por imagem
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Nm] Nome de substância:
0 (Contraceptives, Oral, Hormonal); 0 (Gonadal Steroid Hormones)
[Em] Mês de entrada:1706
[Cu] Atualização por classe:171101
[Lr] Data última revisão:
171101
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:161014
[St] Status:MEDLINE
[do] DOI:10.1152/ajpregu.00190.2016


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Fotocópia
[PMID]:27702883
[Au] Autor:Skytioti M; Søvik S; Elstad M
[Ad] Endereço:Division of Physiology, Institute of Basic Medical Sciences University of Oslo, Oslo, Norway maria.skytioti@medisin.uio.no.
[Ti] Título:Internal carotid artery blood flow in healthy awake subjects is reduced by simulated hypovolemia and noninvasive mechanical ventilation.
[So] Source:Physiol Rep;4(19), 2016 Oct.
[Is] ISSN:2051-817X
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:Intact cerebral blood flow (CBF) is essential for cerebral metabolism and function, whereas hypoperfusion in relation to hypovolemia and hypocapnia can lead to severe cerebral damage. This study was designed to assess internal carotid artery blood flow (ICA-BF) during simulated hypovolemia and noninvasive positive pressure ventilation (PPV) in young healthy humans. Beat-by-beat blood velocity (ICA and aorta) were measured by Doppler ultrasound during normovolemia and simulated hypovolemia (lower body negative pressure), with or without PPV in 15 awake subjects. Heart rate, plethysmographic finger arterial pressure, respiratory frequency, and end-tidal CO (ETCO ) were also recorded. Cardiac index (CI) and ICA-BF were calculated beat-by-beat. Medians and 95% confidence intervals and Wilcoxon signed rank test for paired samples were used to test the difference between conditions. Effects on ICA-BF were modeled by linear mixed-effects regression analysis. During spontaneous breathing, ICA-BF was reduced from normovolemia (247, 202-284 mL/min) to hypovolemia (218, 194-271 mL/min). During combined PPV and hypovolemia, ICA-BF decreased by 15% (200, 152-231 mL/min, P = 0.001). Regression analysis attributed this fall to concurrent reductions in CI (ß: 43.2, SE: 17.1, P = 0.013) and ETCO (ß: 32.8, SE: 9.3, P = 0.001). Mean arterial pressure was maintained and did not contribute to ICA-BF variance. In healthy awake subjects, ICA-BF was significantly reduced during simulated hypovolemia combined with noninvasive PPV Reductions in CI and ETCO had additive effects on ICA-BF reduction. In hypovolemic patients, even low-pressure noninvasive ventilation may cause clinically relevant reductions in CBF, despite maintained arterial blood pressure.
[Mh] Termos MeSH primário: Artéria Carótida Interna/fisiologia
Hipocapnia/complicações
Hipovolemia/complicações
Ventilação não Invasiva/efeitos adversos
Respiração Artificial/efeitos adversos
[Mh] Termos MeSH secundário: Adulto
Pressão Arterial/fisiologia
Velocidade do Fluxo Sanguíneo/fisiologia
Pressão Sanguínea
Artéria Carótida Interna/diagnóstico por imagem
Circulação Cerebrovascular/fisiologia
Feminino
Voluntários Saudáveis
Frequência Cardíaca/fisiologia
Hemodinâmica
Seres Humanos
Hipocapnia/fisiopatologia
Hipovolemia/fisiopatologia
Hipóxia Encefálica/complicações
Hipóxia Encefálica/fisiopatologia
Pressão Negativa da Região Corporal Inferior/efeitos adversos
Masculino
Fluxo Sanguíneo Regional
Ultrassonografia Doppler/métodos
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Em] Mês de entrada:1710
[Cu] Atualização por classe:171026
[Lr] Data última revisão:
171026
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:161006
[St] Status:MEDLINE



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