[Hypoxaemia, peripheral chemoreceptors and fetal heart rate]. / Hypoxémie, chémorécepteurs périphériques et rythme cardiaque fœtal.

The perinatal results of the widespread adoption of the continuous electronic fetal heart rate monitoring during labor remain rather disappointing. This is due in part to a lack of consistent interpretation of the fetal heart tracings. Despite efforts by referral agencies over the past decade the situation has not improved. In defense of practitioners the heterogeneity and complexity of definitions and classifications patterns especially morphological currently proposed should be noted. Whereas with the recent advances in the field of neuroscience, it is now possible to visualize the chain of pathophysiological events that lead from the hypoxemic stimulus of the glomus cell to changes in the morphology of the fetal heart rate tracing. Thus by taking some examples of real situations, we propose a method of analysis that dissects the fetal heart tracing and take into account the functional specifications of the chemoreceptor when exposed to a hypoxic environment. Furthermore we can identify tracings with a "threshold effect" and also "sensitization and desensitization effects" according to the intensity, duration and recurrence of hypoxaemic episodes. This new approach based upon specific research into the mechanism behind the fetal heart rate abnormalities may be useful to complement the morphological study of the fetal heart tracing, to provide a better idea of the fetal status and to better define the indications of fetal blood sampling procedures.

[Global systems for monitoring cerebral hemodynamics in the neurocritical patient: basic concepts, controversies and recent advances in measuring jugular bulb oxygenation]. / Métodos globales de monitorización de la hemodinámica cerebral en el paciente neuricrítico: fundamentos, controversias y actualizaciones en las técnicas de oximetría yugular

Because of the importance of hypoxic/ischemic phenomena in head-injured patients, brain monitoring in these patients should be complemented by systems providing information on cerebral blood flow and metabolism. Indirect estimations of cerebral blood flow have been obtained from blood extracted from the jugular bulb, as a special bedside application of the Fick's principle to the brain. In the last few years, the use of jugular oximetry techniques has become routine in centers treating head-injured and other neurocritical patients such as those presenting subarachnoid hemorrhage or malignant middle cerebral artery infarction. The experience acquired in the use of these techniques, as well as the introduction of new neuromonitoring systems, have deepened our understanding of the information gained and have enabled more precise definition of their indications and limitations. This review describes the basic concepts underlying the use of jugular oximetry techniques in the neurocritical patient. We also explain the reasons why several variables derived from jugular blood such as arterio-jugular differences of lactate (AVDL) or the lactate-oxygen index (LOI) do not provide accurate information on brain metabolism.

Métodos globales de monitorización de la hemodinámica cerebral en el paciente neurocrítico: fundamentos, controversias y actualizaciones en las técnicas de oximetría yugular / Global systems for monitoring cerebral hemodynamics in the neurocritical patient: basic concepts, controversies and recent advances in measuring jugular bulb oxygenation

El papel relevante que la hipoxia tisular cerebral juega en la fisiopatología de los pacientes con un traumatismo craneoencefálico (TCE) justifica la necesidad de complementar la monitorización de estos pacientes con sistemas que aporten información sobre el flujo sanguíneo y el metabolismo cerebral. En la búsqueda de sistemas útiles en la cabecera del paciente, se han utilizado extrapolaciones del principio de Fick al encéfalo, utilizando métodos que estiman el flujo sanguíneo cerebral (FSC) a partir de la obtención de muestras de sangre del bulbo de la yugular. En los últimos años, las técnicas de oximetría yugular se han convertido en elementos de uso frecuente en las unidades que tratan pacientes con un TCE u otros pacientes neurocríticos, como los pacientes con una hemorragia subaracnoidea o con infartos masivos de la arteria cerebral media. El uso frecuente de estas técnicas en las últimas dos décadas, junto a la incorporación de otros sistemas de neuromonitorización, permiten en la actualidad matizar la información que estos métodos globales proporcionan y definir mejor tanto sus indicaciones como sus limitaciones. El objetivo de esta revisión es presentar los fundamentos y los conceptos básicos relacionados con la utilización clínica de las técnicas de oximetría yugular en el paciente neurocrítico. También presentamos y discutimos la evidencia más reciente que indica que determinadas variables, obtenidas de muestras de sangre del bulbo de la yugular, tales como las diferencias arterio-yugulares de lactatos (AVDL) y el índice lactato-oxígeno (LOI), a pesar de su amplia utilización en la práctica clínica diaria, no ofrecen una información fiable sobre el metabolismo cerebral que permita la toma de decisiones terapéuticas

Because of the importance of hypoxic/ischemic phenomena in head-injured patients, brain monitoring in these patients should be complemented by systems providing information on cerebral blood flow and metabolism.Indirect estimations of cerebral blood flow have been obtained from blood extracted from the jugular bulb, as a special bedside application of the Fick’s principle to the brain. In the last few years, the use of jugular oximetry techniques has become routine in centers treating head-injured and other neurocritical patients such as those presenting subarachnoid hemorrhage or malignant middle cerebral artery infarction. The experience acquired in the use of these techniques, as well as the introduction of new neuromonitoring systems, have deepened our understanding of the information gained and have enabled more precise definition of their indications and limitations. This review describes the basic concepts underlying the use of jugular oximetry techniques in the neurocritical patient. We also explain the reasons why several variables derived from jugular blood such as arterio-jugular differences of lactate (AVDL) or the lactate-oxygen index (LOI) do not provide accurate information on brain metabolism