Effects of Positioning on Cerebral Oxygenation

Soeding, Paul

doi:10.1007/s40140-013-0020-y

Cited by 7 publications

(4 citation statements)

References 143 publications

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“…In this study, the larger O 2 Hb drop after a supine-stand transition was not accompanied by a larger BP drop, contrary to existing literature [39]. A lower cerebral oxygenation during sitting and standing could be explained by the differences in hydrostatic pressure gradient between the heart and brain in sitting or standing versus supine position, leading to a small but sustained reduction in cerebral perfusion pressure and thus cerebral oxygen delivery [21,40,41]. Because the cerebral metabolic demand and therefore oxygen consumption remain stable, this results in standing O 2 Hb values below and HHb values above baseline.…”

Section: Resultscontrasting

confidence: 81%

Capturing postural blood pressure dynamics with near-infrared spectroscopy-measured cerebral oxygenation

et al. 2023

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Orthostatic hypotension (OH) is highly prevalent in older adults and associated with dizziness, falls, lower physical and cognitive function, cardiovascular disease, and mortality. OH is currently diagnosed in a clinical setting with single-time point cuff measurements. Continuous blood pressure (BP) devices can measure OH dynamics but cannot be used for daily life monitoring. Near-infrared spectroscopy (NIRS) has potential diagnostic value in measuring cerebral oxygenation continuously over a longer time period, but this needs further validation. This study aimed to compare NIRS-measured (cerebral) oxygenation with continuous BP and transcranial Doppler-measured cerebral blood velocity (CBv) during postural changes. This cross-sectional study included 41 participants between 20 and 88 years old. BP, CBv, and cerebral (long channels) and superficial (short channels) oxygenated hemoglobin (O2Hb) were measured continuously during various postural changes. Pearson correlations between BP, CBv, and O2Hb were calculated over curves and specific characteristics (maximum drop amplitude and recovery). BP and O2Hb only showed good curve-based correlations (0.58–0.75) in the initial 30 s after standing up. Early (30–40 s) and 1-min BP recovery associated significantly with O2Hb, but no consistent associations were found for maximum drop amplitude and late (60–175 s) recovery values. Associations between CBv and O2Hb were poor, but stronger for long-channel than short-channel measurements. BP associated well with NIRS-measured O2Hb in the first 30 s after postural change. Stronger associations for CBv with long-channel O2Hb suggest that long-channel NIRS specifically reflects cerebral blood flow during postural transitions, necessary to better understand the consequences of OH such as intolerance symptoms.

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Section: Resultscontrasting

confidence: 81%

Capturing postural blood pressure dynamics with near-infrared spectroscopy-measured cerebral oxygenation

et al. 2023

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“…The cerebral blood volume is presumed to increase on the dependent lung side while in the lateral decubitus position. [ 27 ] Blauenstein et al [ 29 ] reported that in healthy right-hand dominant patients, the CBF in the inferior frontal region is higher in the right hemisphere than in the left hemisphere. Although it has been reported that midazolam decreases the CBF in the left prefrontal cortex, we found no evidence that propofol or desflurane affects the laterality of the cerebral blood volume.…”

Section: Discussionmentioning

confidence: 99%

“…The bilateral SjO 2 values did not differ to a statistically significant extent in healthy patients in the supine position; however, postural change during anesthesia, such as adopting the Trendelenburg or beach chair positions, generally affects cerebral circulation. [27,28] In the present study, patients were placed in the lateral decubitus position with bending of the surgical table. The cerebral blood volume is presumed to increase on the dependent lung side while in the lateral decubitus position.…”

Section: Discussionmentioning

confidence: 99%

Comparison of regional cerebral oxygen saturation during one-lung ventilation under desflurane or propofol anesthesia: A randomized trial

et al. 2022

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Background: During one-lung ventilation (OLV), deterioration of pulmonary oxygenation reduces arterial oxygen saturation and cerebral oxygen saturation (rSO 2 ). However, oxidative stress during OLV causes lung injury, so the fraction of inspiratory oxygen (FiO 2 ) should be kept as low as possible. We investigated the changes in rSO 2 under propofol or desflurane anesthesia while percutaneous oxygen saturation (SpO 2 ) was kept as low as possible during OLV. Methods: Thirty-six patients scheduled for thoracic surgery under OLV in the lateral decubitus position were randomly assigned to propofol (n = 19) or desflurane (n = 17) anesthesia. FiO 2 was set to 0.4 at the start of surgery under two-lung ventilation (measurement point: T3) and then adjusted to maintain an SpO 2 of 92% to 94% after the initiation of OLV. The primary outcome was the difference in the absolute value of the decrease in rSO 2 from T3 to 30 minutes after the initiation of OLV (T5), which was analyzed by an analysis of covariance adjusted for the rSO 2 value at T3. Results: The mean rSO 2 values were 61.5% ± 5.1% at T3 and 57.1% ± 5.3% at T5 in the propofol group and 62.2% ± 6.0% at T3 and 58.6% ± 5.3% at T5 in the desflurane group. The difference in the absolute value of decrease between groups (propofol group − desflurane group) was 0.95 (95% confidence interval, [−0.32, 2.2]; P = .152). Conclusions: Both propofol and desflurane anesthesia maintain comparable cerebral oxygenation and can be used safely, even when the SpO 2 is kept as low as possible during OLV.

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“…Besides the effect of the drugs administered during general anesthesia in CBF, other events might also alter the blood supply to the brain, as for example patient positioning [92]. Kose at el.…”

Section: Additional Drugs Administered During General Anesthesiamentioning

confidence: 99%

Development of new algorithms for depth of anesthesia monitoring integrating cerebral blood flow estimations

González Pijuán

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Cerebral blood flow (CBF) reflects the rate of delivery of arterial blood to the brain. Since no nutrients, oxygen or water can be stored in the cranial cavity due to space and pressure restrictions, a continuous perfusion of the brain is critical for survival. Anesthesia is known to affect cerebral hemodynamics , but CBF is only monitored in critical patients due to the lack of a continuous and affordable bedside monitor for this purpose. This Thesis propases a potential solution through bioelectrical impedance, also known as rheoencephalography (REG), that could fill the existing gap for a low-cost and effective CBF monitor. The underlying hypothesis is that REG signals carry information on CBF that might be recovered by means of the application of advanced signal processing techniques, allowing to track CBF changes during anesthesia. Firstly, clinical and technical information related to other CBF monitoring methods and signal processing algorithms suitable for REG signals are provided. Subsequently, clinical data collected under the scope of this project and used to develop and validate the techniques applied to REG signals are described. As a first step in the analysis of REG signals, different filter options for noise removal are presented, in the linear and nonlinear domain. The nonlinear filler applied to the signal attractor showed a better accuracy, mainly in noisy environments, but its computational burden compromises its use in real time monitoring of physiological signals. The analysis of REG starts with the use of geometric features extracted from the time domain, which is the standard processin strategy for this type of data. Geometric features are tested for their ability to detect apneas in young healthy volunteers and to distinguish between different anesthetic depths. Their performance is poor in apnea detection, but they are capable oftracking cerebral hemodynamic changes during anesthesia. Two new approaches are proposed, one based on the nonlinear dynamics of REG signals, extracting the descriptors ofthe attractors reconstructed form REG signals, and one based on entropy rates. Both show significant differences between apnea and baseline recordings, as well as between different anesthetic states. This is a key finding, providing an alternative to Standard processing of REG signals and supporting the hypothesis that REG signals carry CBF information. Among the three proposed techniques, the parameters allowing real time data processing are used to classify REG recordings collected in awake and anesthetized patients. An accuracy of 70% is reached, indicating that CBF changes in REG are related to the anesthetic state of the patient but presenting large variabilities. REG parameters should not aim at replacing depth of anesthesia monitors but should rather help maintaining cerebral hemodynamic stability during anesthesia. Hence, the relationship between global hemodynamics, cerebral hemodynamics and EEG parameters are analyzed, looking for causal relationships among them. lnteractions are detected during steady state anesthesia, anesthetic drug infusion and patient positioning, providing evidence of the coupling between hemodynamics and brain activity. As a conclusion, alternative methods for REG processing that confirm the hypothesis that REG signals carry CBF information are provided. The simplicity of the technology and its low cost and easily interpretable outcomes should provide a new opportunity for REG to reach standard clinical practice. Moreover, causal relationships among the hemodynamic physiological signals and brain activity are assessed, suggesting that the inclusion of REG information in depth of anesthesia monitors could be of valuable use for an affordable, noninvasive bedside tool to prevent unwanted CBF alterations during anesthetic procedures. El flujo sanguíneo cerebral (FSC) refleja el suministro de sangre arterial al cerebro. Como no se pueden guardar nutrientes, oxigeno ni agua en la cavidad craneal por restricciones de espacio y presión, una perfusión continua es fundamental para la supervivencia. La anestesia afecta la hemodinámica cerebral, pero el FSC sólo se monitoriza en pacientes críticos porque no existen dispositives de cabecera, con monitorización continua y a precios asequibles. Esta Tesis propone una posible solución a través de la impedancia bioeléctrica o rheoencefalografia (REG), que puede ocupar el vacío existente en la monitorización del FSC efectiva y de bajo coste. La hipótesis subyacente es que REG tiene información de FSC que podría recuperarse aplicando técnicas avanzadas de procesado, permitiendo detectar las alteraciones de FSC en anestesia. En primer lugar, se presenta una revisión de la literatura, con información clínica y técnica relevante de métodos de monitorización de FSC y algoritmos de procesado de señal aplicables a señales REG. A continuación se describen los datos clínicos recogidos en el ámbito de este proyecto, usados para desarrollar y validar las técnicas aplicadas a señales REG. Como primer paso en el análisis de REG, se presentan distintas opciones de filtros de eliminación de ruido, en el dominio lineal y no lineal. El filtro no lineal aplicado al atractor de la señal ofrece una mayor precisión, especialmente en ambientes muy ruidosos, però su carga computacional compromete su uso para monitorización en tiempo real de señales fisiológicas. El análisis de las señales REG empieza con el estudio de características geométricas extraídas del dominio temporal, la técnica de procesado más común para este tipo de datos. Se evalúa la capacidad de dichas características para detectar apneas en voluntarios jóvenes sanos y para distinguir entre distintas profundidades anestésicas. Su rendimiento es pobre en la detección de apneas, pero son capaces de detectar cambios hemodinámicos cerebrales durante la anestesia. Se proponen dos nuevos enfoques, uno basado en la evaluación de dinámicas no lineales de señales REG, extrayendo los descriptores de los atractores reconstruidos a partir de señales REG, y otro basado en medidas de entropía. Ambos muestran diferencias significativas entre apneas y registros basales, así como entre diferentes estados de anestesia. Éste es un hallazgo clave que proporciona una alternativa al procesado estándar de señales REG y sugiere que las señales REG contienen información de FSC. Entre las tres técnicas propuestas, los parámetros que pueden ser procesados en tiempo real se usan para clasificar señales REG de pacientes despiertos y anestesiados. Se obtiene una precisión del 70%, indicando que los cambios de FSC detectados en REG están relacionados con el estado anestésico del paciente, aunque presentan mucha variabilidad. Los parámetros REG no deben pretender sustituir la monitorización de la profundidad anestésica, pero sí ayudar a mantener la estabilidad hemodinámica durante la anestesia. Por ello se analizan las interacciones entre la hemodinámica global, la cerebral, y parámetros de EEG, buscando nexos de causalidad entre ellos. Se detectan interacciones en anestesia estable, en la administración de anestésicos y cambios de posición del paciente, demostrando que existe una interacción entre la hemodinàmica y la actividad cerebral. En conclusión, esta Tesis aporta métodos alternativos de procesado de REG que confirman la hipótesis de que éstas señales tienen información de FSC. La simplicidad de la tecnología, su bajo precio y resultados fáciles de interpretar deberían dar a REG una nueva oportunidad para alcanzar la práctica clínica. Además, las relaciones de causalidad entre la hemodinámica y la actividad cerebral sugieren que incluir REG en monitores de profundidad anestésica puede ser útil para un monitor

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Effects of Positioning on Cerebral Oxygenation

Cited by 7 publications

References 143 publications

Capturing postural blood pressure dynamics with near-infrared spectroscopy-measured cerebral oxygenation

Capturing postural blood pressure dynamics with near-infrared spectroscopy-measured cerebral oxygenation

Comparison of regional cerebral oxygen saturation during one-lung ventilation under desflurane or propofol anesthesia: A randomized trial

Development of new algorithms for depth of anesthesia monitoring integrating cerebral blood flow estimations

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