RESUMO
BACKGROUND: Para-sympathetic vagal activation has profound influence on heart rate and other cardiovascular parameters. We tested the hypothesis that transcutaneous Vagal Nerve Stimulation (tVNS) through the auricular branch of the vagus nerve would attenuate the normal sympathetic response to central blood volume reduction by lower body negative pressure (LBNP). METHOD: 10 healthy volunteers (6 female; age 21 ± 2 years; weight 62 ± 13 kg; height 167 ± 12 cm) were included in this cross-over design trial. After 15 min rest in supine position, subjects underwent three 15-min periods of 30 mmHg LBNP intervention with and without cyclic tVNS stimulation. Continuous cardiovascular parameters (Nexfin) were recorded. RESULTS: Overall tVNS did not convincingly attenuate sympathetic response to central hypovolemia. Deactivation of the tVNS during LBNP resulted in increased MAP at 2.3 ± 0.5 mmHg (P < 0.001). Comparing the cyclic actual active stimulation periods to periods with pause during tVNS intervention showed a decrease in HR by 72.9 ± 11.2 to 70.2 ± 11.6 bpm (mean ± SD; P < 0.05), and concomitant increases in SV (86.0 ± 12.1 to 87.2 ± 12.6 mL; P < 0.05), MAP (82.9 ± 6.3 to 84.0 ± 6.2 mmHg; P < 0.05) and TPR (1116.0 ± 111.1 to 1153 ± 104.8 dyn*s/cm5; P < 0.05). CONCLUSION: tVNS in 30 s cycles during LBNP can selectively attenuate HR, prompting a compensatory augmented sympathetic response. It would appear the method used in this study at least, has an isolated cardiac inhibitory effect probably mediated by augmented vagal activity on the sinoatrial or atrio-ventricular node, possibly in combination with reduced activity in the sympathetic cardiac nerve.
Assuntos
Estudos Cross-Over , Frequência Cardíaca , Pressão Negativa da Região Corporal Inferior , Estimulação Elétrica Nervosa Transcutânea , Estimulação do Nervo Vago , Humanos , Feminino , Masculino , Estimulação do Nervo Vago/métodos , Pressão Negativa da Região Corporal Inferior/métodos , Estimulação Elétrica Nervosa Transcutânea/métodos , Adulto Jovem , Frequência Cardíaca/fisiologia , Pressão Sanguínea/fisiologia , Adulto , Nervo Vago/fisiologia , Sistema Nervoso Simpático/fisiologiaRESUMO
BACKGROUND: The Compensatory Reserve Metric (CRM) provides a time sensitive indicator of hemodynamic decompensation. However, its in-field utility is limited because of the size and cost-intensive nature of standard vital sign monitors or photoplethysmographic volume-clamp (PPG VC ) devices used to measure arterial waveforms. In this regard, photoplethysmographic measurements obtained from pulse oximetry may serve as a useful, portable alternative. This study aimed to validate CRM values obtained using pulse oximeter (PPG PO ). METHODS: Forty-nine healthy adults (25 females) underwent a graded lower body negative pressure (LBNP) protocol to simulate hemorrhage. Arterial waveforms were sampled using PPG PO and PPG VC . The CRM was calculated using a one-dimensional convolutional neural network. Cardiac output and stroke volume were measured using PPG VC . A brachial artery catheter was used to measure intra-arterial pressure. A three-lead electrocardiogram was used to measure heart rate. Fixed-effect linear mixed models with repeated measures were used to examine the association between CRM values and physiologic variables. Log-rank analyses were used to examine differences in shock determination during LBNP between monitored hemodynamic parameters. RESULTS: The median LBNP stage reached was 70 mm Hg (range, 45-100 mm Hg). Relative to baseline, at tolerance, there was a 47% ± 12% reduction in stroke volume, 64% ± 27% increase in heart rate, and 21% ± 7% reduction in systolic blood pressure ( p < 0.001 for all). Compensatory Reserve Metric values obtained with both PPG PO and PPG VC were associated with changes in heart rate ( p < 0.001), stroke volume ( p < 0.001), and pulse pressure ( p < 0.001). Furthermore, they provided an earlier detection of hemodynamic shock relative to the traditional metrics of shock index ( p < 0.001 for both), systolic blood pressure ( p < 0.001 for both), and heart rate ( p = 0.001 for both). CONCLUSION: The CRM obtained from PPG PO provides a valid, time-sensitized prediction of hemodynamic decompensation, opening the door to provide military medical personnel noninvasive in-field advanced capability for early detection of hemorrhage and imminent onset of shock. LEVEL OF EVIDENCE: Diagnostic Tests or Criteria; Level III.
Assuntos
Pressão Negativa da Região Corporal Inferior , Oximetria , Fotopletismografia , Humanos , Masculino , Feminino , Adulto , Oximetria/métodos , Pressão Negativa da Região Corporal Inferior/métodos , Fotopletismografia/métodos , Monitorização Fisiológica/métodos , Monitorização Fisiológica/instrumentação , Volume Sistólico/fisiologia , Frequência Cardíaca/fisiologia , Voluntários Saudáveis , Débito Cardíaco/fisiologia , Hemodinâmica/fisiologia , Adulto Jovem , Hemorragia/diagnóstico , Hemorragia/fisiopatologia , Eletrocardiografia/métodosRESUMO
Patients with refractory intracranial hypertension who have already undergone all the measures recommended by the current guidelines can benefit from having their intraabdominal pressure monitored since its increase generates hemodynamic repercussions and secondary elevation of intracranial pressure. In this context, a bibliographic research was performed on PubMed with the terms intra-abdominal pressure, abdominal compartment syndrome, intracranial pressure, intracranial hypertension. Altogether, 146 articles were observed, 87 of which were from the year 2000, and only 15 articles were considered relevant to the topic. These studies indicate that patients with refractory intracranial hypertension can benefit fromthe measurement of intraabdominal pressure, since there is evidence that an increase in this pressure leads to organic dysfunctions with an indirect impact on cerebral venous return and, consequently, an increase in intracranial pressure. In thosewho underwent decompression laparotomy, direct effectswere observed in reducing intracranial hypertension and survival.
Assuntos
Hipertensão Intracraniana/prevenção & controle , Hipertensão Intra-Abdominal/complicações , Hipertensão Intra-Abdominal/terapia , Monitorização Hemodinâmica , Hipertensão Intra-Abdominal/prevenção & controle , Laparotomia/métodos , Pressão Negativa da Região Corporal Inferior/métodosRESUMO
O acesso à luz do estômago e do jejuno proximal por meio de gastrostomia e jejunostomia, respectivamente, de forma temporária ou definitiva, está indicado diante da necessidade prolongada de descompressão digestiva ou de suporte alimentar. O emprego desses procedimentos expandiu-se nos últimos 25 anos com a introdução da gastrostomia endoscópica, especialmente em pacientes com afecções neurológicas de evolução progressiva e neoplasias avançadas. Este artigo aborda aspectos conceituais da gastrostomia e jejunostomia, as principais indicações, as vias de acesso preferenciais em diferentes cenários clínicos e as modalidades técnicas frequentemente empregadas. O manejo dessas estomias, os resultados e as potenciais complicações também são enfatizados. Finalmente, os fundamentos éticos e legais da ampliação da indicação da gastrostomia e da jejunostomia como procedimentos paliativos são discutidos.
A temporary or permanent access to the stomach or jejunum, through a gastrostomy or jejunostomy, is indicated whenever nutritional support or prolonged decompression of the upper alimentary tract is needed. With the introduction of endoscopic gastrostomy, the utilization of these procedures has increased in the last 25 years, specially in patients with progressive neurologic diseases and in those with advanced cancer. This article deals with the conceptual aspects of gastrostomies and jejunostomies, its primary indications, the preferential means of access in different clinical scenarios as well as the technical modalities most frequently used. The management of the stomas, the results and potential complications are also highlighted. Finally, the ethical and legal implications of greater utilization of these procedures in a palliative setting are also discussed.
Assuntos
Cuidados Paliativos , Gastrostomia , Jejunostomia , Nutrição Enteral , Pressão Negativa da Região Corporal InferiorRESUMO
Dentre o amplo espectro das chamadas feridas complexas a úlcera por pressãopode ser definida como uma lesão localizada, acometendo pele e/ou tecidos subjacentes, usualmente sobre uma proeminência óssea, resultante de pressão, ou pressão associada a cisalhamento e/ou fricção. Os fatores de risco para úlceras por pressão são todos aqueles que predispõem o indivíduo a períodos prolongados de isquemia induzida por pressão, e que reduzem a capacidade de recuperação tecidual da lesão isquêmica, podendo ter fatoresassociados intrínsecos ou extrínsecos. A classificação de ulceras por pressão e as medidas de prevenção são inúmeras. Contudo, para ulceras por pressão com complicações ou profundidades avançadas o tratamento determinante na sua resolução é o cirúrgico. Nos últimos anos, a introdução da pressão negativa para o tratamento de feridas complexas, como são para muitas úlceras por pressão, foi muito importante como adjuvante no tratamento cirúrgico...
Among the broad spectrum of complex wounds the pressure ulcer can be defined as a localized lesion, affecting the skin and/or underlying tissue usually over a bony prominence,resulting from pressure or pressure combined with shear and/or friction. Risk factors for pressure ulcers are those that predispose an individual to prolonged periods of ischemia induced by pressure, and reduce the ability of the tissue recovery of a ischemic injury, which can have associated factors, intrinsic or extrinsic. The classification of pressure ulcers and prevention scales are numerous. However, for pressure ulcers with complications or advanced depths the determinant treatment is surgery. In recent years, the introduction of negative pressuredressing for treatment of complex wounds, as are many pressure ulcers, was very important as an adjuvant therapy surgery...
Assuntos
Humanos , Pressão Negativa da Região Corporal Inferior , Úlcera por Pressão/cirurgia , Úlcera por Pressão/prevenção & controle , Cirurgia Plástica , Pele/lesõesRESUMO
The first minutes of the time course of cardiopulmonary reflex control evoked by lower body negative pressure (LBNP) in patients with hypertensive cardiomyopathy have not been investigated in detail. We studied 15 hypertensive patients with left ventricular dysfunction (LVD) and 15 matched normal controls to observe the time course response of the forearm vascular resistance (FVR) during 3 min of LBNP at -10, -15, and -40 mmHg in unloading the cardiopulmonary receptors. Analysis of the average of 3-min intervals of FVR showed a blunted response of the LVD patients at -10 mmHg (P = 0.03), but a similar response in both groups at -15 and -40 mmHg. However, using a minute-to-minute analysis of the FVR at -15 and -40 mmHg, we observed a similar response in both groups at the 1st min, but a marked decrease of FVR in the LVD group at the 3rd min of LBNP at -15 mmHg (P = 0.017), and -40 mmHg (P = 0.004). Plasma norepinephrine levels were analyzed as another neurohumoral measurement of cardiopulmonary receptor response to LBNP, and showed a blunted response in the LVD group at -10 (P = 0.013), -15 (P = 0.032) and -40 mmHg (P = 0.004). We concluded that the cardiopulmonary reflex response in patients with hypertensive cardiomyopathy is blunted at lower levels of LBNP. However, at higher levels, the cardiopulmonary reflex has a normal initial response that decreases progressively with time. As a consequence of the time-dependent response, the cardiopulmonary reflex response should be measured over small intervals of time in clinical studies.
Assuntos
Humanos , Masculino , Feminino , Adulto , Pessoa de Meia-Idade , Barorreflexo , Hipertensão/fisiopatologia , Pressorreceptores/fisiopatologia , Resistência Vascular , Disfunção Ventricular Esquerda/fisiopatologia , Estudos de Casos e Controles , Antebraço/irrigação sanguínea , Hemodinâmica , Hipertensão/sangue , Pressão Negativa da Região Corporal Inferior , Norepinefrina/sangue , Fatores de Tempo , Disfunção Ventricular Esquerda/sangueRESUMO
La ascitis a tensión ocasiona insuficiencia respiratoria mecánica al dificultar el descenso del diafragma; la paracentesis evacuadora debe mejorar este cuadro. El objetivo del trabajo fue determinar el efecto de la paracentesis evacuadora sobre las pruebas de función respiratoria en el enfermo con ascitis a tensión. En un grupo de 15 sujetos con ascitis a tensión (secundaria a cirrosis hepática) que provocó dificultad respiratoria se realizaron gasometría arterial, medición del perímetro abdominal y pruebas de función respiratoria previa y posteriormente (dos y 24 h) a la realización de paracentesis evacuadora de tres litros de líquido de ascitis. En ninguno de los casos el paciente se encontraban en encefalopatía hepática o sangrado de tubo digestivo alto. El método estadístico empleado fue t de Student. En los 15 sujetos hubo disminución del perímetro abdominal de 3 cm en promedio, así como resolución de los síntomas respiratorios. En la gasometría arterial hubo elevación de paO2, en promedio 5 mmHg (p< 0.005), la saturación de O2 mejoró 2.61 por ciento (p< 0.05). En las pruebas de función respiratoria todos los sujetos mostraron un patrón obstuctivo. La velocidad máxima de flujo a la exhalación (VMFE) mejoró en promedio 0.2 y 0.4 l/seg a las dos y 24 h (p < 0.001), la capacidad vital forzada (CVF) disminuyó 0.36 y 0.25 l respectivamente (p < 0.5 en ambos valores), el volumen espiratorio forzado del primer segundo (VEF1) subió 0.01 y 0.4 l (p< 0.05 y < 0.005), y la relación CVE/VEF1 se elevó 8.7 y 13 por ciento (p< 0.05 y < 0.005). Característicamente los pacientes que obtuvieron un menor beneficio de la paracentesis eran fumadores. La paracentesis es un método eficaz para mejorar la función respiratoria del sujeto con ascitis a tensión