Search results for "cerebrovascular circulation"

Initiation of high-frequency oscillatory ventilation and its effects upon cerebral circulation in pigs: an experimental study

2006

BACKGROUND: Current practice at high-frequency oscillatory ventilation (HFOV) initiation is a stepwise increase of the constant applied airway pressure to achieve lung recruitment. We hypothesized that HFOV would lead to more adverse cerebral haemodynamics than does pressure controlled ventilation (PCV) in the presence of experimental intracranial hypertension (IH) and acute lung injury (ALI) in pigs with similar mean airway pressure settings. METHODS: In 12 anesthetized pigs (24-27 kg) with IH and ALI, mean airway pressure (P(mean)) was increased (to 20, 25, 30 cm H(2)O every 30 min), either with HFOV or with PCV. The order of the two ventilatory modes (cross-over) was randomized. Mean art…

High dose naloxone does not improve cerebral or myocardial blood flow during cardiopulmonary resuscitation in pigs

1997

In a prospective, randomized, placebo-controlled, double-blind trial we tested the hypothesis that naloxone given during cardiopulmonary resuscitation (CPR) enhances cerebral and myocardial blood flow. Twenty-one anesthetized, normoventilated pigs were instrumented for measurements of right atrial and aortic pressures, and regional organ blood flow (radiolabeled microspheres). After 5 min of untreated fibrillatory arrest, CPR was commenced using a pneumatic chest compressor/ventilator. With onset of CPR, an i.v. bolus of 40 micrograms/kg b.w. of epinephrine was given, followed by an infusion of 0.4 micrograms/kg per min. After 5 min of CPR, either naloxone, 10 mg/kg b.w. (group N, n = 11) o…

Sevoflurane Impairs Cerebral Blood Flow Autoregulation in Rats: Reversal by Nonselective Nitric Oxide Synthase Inhibition

2005

UNLABELLED In this study, we investigated the effects of 1.0 and 2.0 minimum alveolar anesthetic concentration (MAC) sevoflurane on cerebral blood flow (CBF) autoregulation before and after nonselective inhibition of nitric oxide (NO) synthase in rats. Rats were randomly assigned as follows: Group 1 (n = 8): 1.0 MAC sevoflurane; Groups 2 and 3 (n = 8 per group): 2.0 MAC sevoflurane. Assessment of autoregulation within a mean arterial blood pressure range of 140-60 mm Hg was performed by graded hemorrhage before and after administration of l-arginine methyl ester (l-NAME, 30 mg/kg IV, Groups 1 and 2) or during hypocapnia (Group 3). In 10 additional animals, brain tissue NO(2)(-) concentratio…

Sevoflurane-induced reduction of bispectral index does not affect human cerebral microcirculation

2015

Inhalational or intravenous anesthetics for craniotomies? Pro inhalational.

2006

In neurosurgery, anesthesiologists and surgeons focus on the same target - the brain. The nature of anesthetics is to interact with brain physiology, leading to favorable and adverse effects. Research in neuroanesthesia over the last three decades has been dedicated to identifying the optimal anesthetic agent to maintain coupling between cerebral blood flow and metabolism, keep cerebrovascular autoregulation intact, and not increase cerebral blood volume and intracranial pressure.Sevoflurane is less vasoactive than halothane, enflurane, isoflurane, or desflurane. The context sensitive half-life is short and similar to that of desflurane, which translates into fast on and offset. Compared wi…

Algorithms for the inference of causality in dynamic processes: Application to cardiovascular and cerebrovascular variability

2015

This study faces the problem of causal inference in multivariate dynamic processes, with specific regard to the detection of instantaneous and time-lagged directed interactions. We point out the limitations of the traditional Granger causality analysis, showing that it leads to false detection of causality when instantaneous and time-lagged effects coexist in the process structure. Then, we propose an improved algorithm for causal inference that combines the Granger framework with the approach proposed by Pearl for the study of causality among multiple random variables. This new approach is compared with the traditional one in theoretical and simulated examples of interacting processes, sho…

Oxidative stress upregulates the NMDA receptor on cerebrovascular endothelium.

2009

N-methyl-d-aspartate receptor (NMDA-R)-mediated oxidative stress has been implicated in blood-brain barrier (BBB) disruption in a variety of neuropathological diseases. Although some interactions between both phenomena have been elucidated, possible influences of reactive oxygen species (ROS) on the NMDA-R itself have so far been neglected. The objective of this study was to examine how the cerebroendothelial NMDA-R is affected by exposure to oxidative stress and to assess possible influences on BBB integrity. RT-PCR confirmed several NMDA-R subunits (NR1, NR2B-D) expressed in the bEnd3 cell line (murine cerebrovascular endothelial cells). NR1 protein expression after exposure to ROS was ob…

Heterogeneity of P2-Purinoceptors in Brain Circulation

1990

The existence of P2-purinoceptors in the cerebrovascular bed was examined by testing the effects of ATP and its stable analog, α,β-methylene-ATP, on CBF in the unanesthetized goat as well as on isometric tension in isolated goat middle cerebral artery. When injected directly into the cerebral circulation, ATP increased and α,β-methylene-ATP decreased CBF. Indomethacin did not modify either of these effects. The vasoconstrictor action of α,β-methylene-ATP was reduced by nicardipine. “In vitro,” both ATP and α,β-methylene-ATP contracted the cerebral arteries at resting tone, but the analog was more potent than ATP. Repeated application of α,β-methylene-ATP as well as indomethacin significant…

Acute electrocorticographic changes following localized cortical freezing in the cat. Preliminary report.

1968

Monitoring of cortical blood flow: Clinical relevance of experimental laser Doppler studies

1996

Continuous monitoring of cortical blood flow provides real time information of CBF-changes during neurosurgical operations and on the neurointensive care unit. Laser Doppler flowmetry is a continuous, noninvasive technique suitable for measurement of the cortical microcirculation. In a number of experimental studies we have analyzed the characteristics of this method for cortical blood flow monitoring. The high spatial resolution of laser Doppler flowmetry and the heterogeneity of the cortical microvascular network results in a scatter of flow values over a wide range depending on the site of measurement. Data collection from different spots and calculation of frequency histogram may serve …