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Results for “CEREBROVASCULAR CIRCULATION”

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At least 163 records · Page 9Linked to original sources

PubMedDate not supplied

[Rheoencephalographic evaluation of cerebrovascular circulation in cases of ruptured intracranial aneurysms and after carotid artery ligation].

Rheoencephalographic (REG) investigations were performed in patients with ruptured intracranial aneurysms before and after common carotid artery ligation and in a group of healthy subjects. REG curves after ligation of the common carotid artery showed lowering of the amplitude of waves on the side of ligation and generalized vasospasm of varying intensity and different degree of penetration into the cerebral structures. These changes were more intensive on the side of ligation and persisted for over 2 weeks. REG is a valuable method for early diagnosis of vascular disturbances in acute postoperative period in these operations.

Adult↗

PubMedDate not supplied

[Reduction of erythrocyte deformability in Krushinskiĭ-Molodkina rats in acute hemorrhagic cerebrovascular circulation disorders].

The ability of erythrocytes to change their shapes in the shear flow under acute strokes of hemorrhagic type in rats of the Krushinsky-Molodkina line was studied. The rigidity of membranes and the internal viscosity of erythrocytes were investigated by the laser diffraction method. The method consists in obtaining diffraction images from a thin layer of a dilute suspension of erythrocytes moving in the shear flow and subsequent computer processing of these images. It was shown that strokes of hemorrhagical type in rats of the Krushinsky-Molodkina line cause a reduction in the ability of erythrocytes to change theirs shapes.

Acoustic Stimulation↗

PubMedDate not supplied

[Pethidine analgesia and cerebrovascular circulation in very small premature infants].

Aim of the study was the assessment of possible side effects of analgesia with pethidine on the intracerebral circulation of very immature preterm infants. For this purpose the blood flow velocity in the internal carotid artery, basilar cerebral artery and the anterior cerebral artery was measured by pulsed Dopplersonography before and 5-10 min after i.v. injection of 1.0 mg/kg pethioine on 10 preterm infants with a gestational age of 24-30 weeks. Furthermore values for the parameter mean arterial blood pressure, heart frequency and tcpCO2 were obtained. None of the measured parameters showed a significant difference with the i.v. bolus injection of pethidine. As even very immature preterm infants do feel pain and can show potential dangerous physiological pain reactions and as this study proves the tolerance of the drug, analgesia with morphine derivates is recommended.

Blood Flow Velocity↗

PubMed1996

[Measurement of human cerebrovascular circulation. Comparison of Kety-Schmidt technique with the intravenous 133-xenon clearance technique].

UNLABELLED: In this study cerebral blood flow (CBF) was simultaneously measured with the Kety-Schmidt method and the intravenous 133Xe clearance technique. CBF, cerebral metabolic rate of oxygen (CMRO2), and CO2 reactivity of CBF were compared under fentanyl-midazolam anaesthesia and varying paCO2 levels. METHODS: Thirteen male patients were studied before they underwent coronary artery bypass surgery. For measurement of CBF with the Kety-Schmidt inert gas saturation technique, argon was used as indicator instead of nitrous oxide, because argon is less soluble in water and lipid such that arterial and hence organ saturation is attained earlier. Wash-in periods of 10 min were used for all measurements. For measurement of CBF with the intravenous xenon method 10 scintillation detectors placed lateral to the skull and an air detector for calculation of tracer recirculation were used. 10-15 mCi of 133Xe dissolved in physiological saline was injected via a peripheral i.v. cannula. For comparison with the Kety-Schmidt technique CBF15-values representing the flow of the grey and white matter were chosen. CBF was measured simultaneously with both methods under normocapnic (paCO2 43 +/- 3 mmHg), hypocapnic (paCO2 31 +/- 3 mmHg), and under hypercapnic (paCO2 54 +/- 4 mmHg) conditions. RESULTS: All CBF15 values obtained with the intravenous xenon method were significantly lower than the corresponding CBF-values measured with the Kety-Schmidt technique: by 36% under normocapnic, 23% under hypocapnic, and 39% under hypercapnic conditions, respectively. Hence, CMRO2 values calculated from CBF values obtained with the xenon method were reduced to about the same degree as those derived from CBF values measured with the Kety-Schmidt technique. There was no significant correlation between the CBF values of either method (y = 1.82x-8.58,r = 0.76 P = 0.357). Non-linear curve-fitting procedures yielded exponential CBF-paCO2 relationships for both methods, although the relative carbon dioxide reactivity was higher with the Kety-Schmidt technique than with the xenon method (y = 8.14 e0.039x vs y = 10,75 e0.023x). CONCLUSIONS: Most probably due to contamination with radioactivity from slowly perfused extracerebral tissues the intravenous 133Xe-clearance technique underestimates CBF, CMRO2, and cerebrovascular CO2 reactivity, at least when CBF15 values are used as flow parameters.

Adjuvants, Anesthesia↗

PubMed1975

[Action mechanism and effects of ifenprodil on the regional blood flow, especially on cerebrovascular circulation].

Effects of ifenprodil on the regional blood flow of some organs (skin, skeletal muscle, liver, myocardium, kidney, cerebral cortex, hippocampus, amygdala, hypothalamus and cerebellar cortex) of the curarized cat under artificial respiration were studied using the thermoelectrical method. 1) Blood flow in the skin decreased, whereas renal blood flow increased. 2) Blood flow in the liver showed a biphasic response, being more active in the increasing phase. 3) Blood flow in the hypothalamus and cerebellar cortex (vertebral arterial region), skeletal muscle and myocardium markedly increased. 4) Blood flow in the cerebral cortex and hippocampus (external carotid arterial region) was not influenced by ifenprodil, but slight changes were noticed and were dependent on the blood pressure response. 5) Blood pressure fell in accordance with the dose level of ifenprodil given i.v. 6) Those results suggest that the mechanisms of action of ifenprodil are alpha-adrenergic blocking, beta-mimetic and direct vasodilating. A cholinergic effect was also suggested. 7) On certain functions such as blood flow in the skin and blood pressure a dual action, that is alpha adreno-mimetic and -lytic was seen. 8) Concerning the vascular smooth muscle relaxative action, it would appear that ifenprodil has not only a direct effect but also a secondary effect resulting presumably from its action on the local metabolism.

Amygdala↗

PubMed1999

Critical closing pressure in cerebrovascular circulation.

OBJECTIVE: Cerebral critical closing pressure (CCP) has been defined as an arterial pressure threshold below which arterial vessels collapse. Hypothetically this is equal to intracranial pressure (ICP) plus the contribution from the active tone of cerebral arterial smooth muscle. The correlation of CCP with ICP, cerebral autoregulation, and other clinical and haemodynamic modalities in patients with head injury was evaluated. METHOD: intracranial pressure, arterial blood pressure (ABP) and middle cerebral artery blood flow velocity were recorded daily in ventilated patients. Waveforms were processed to calculate CCP, the transcranial Doppler-derived cerebral autoregulation index (Mx), mean arterial pressure (ABP), intracranial pressure (ICP), and cerebral perfusion pressure (CPP). RESULTS: Critical closing pressure reflected the time related changes in ICP during plateau and B waves. Overall correlation between CCP and ICP was mild but significant (R=0.41; p<0.0002). The mean difference between ABP and CCP correlated with CPP (R=0.57, 95% confidence interval (95% CI) for prediction 25 mm Hg). The difference between CCP and ICP, described previously as proportional to arterial wall tension, correlated with the index of cerebral autoregulation Mx (p<0.0002) and CPP (p<0.0001). However, by contrast with the Mx index, CCP-ICP was not significantly correlated with outcome after head injury. CONCLUSION: Critical closing pressure, although sensitive to variations in ICP and CPP, cannot be used as an accurate estimator of these modalities with acceptable confidence intervals. The difference CCP-ICP significantly correlates with cerebral autoregulation, but it lacks the power to predict outcome after head injury.

Adolescent↗

PubMed1995

[Effects of analgesia and sedation on cerebrovascular circulation, cerebral blood volume, cerebral metabolism and intracranial pressure].

Cerebral blood flow autoregulation, CO2 reactivity and the pressure-volume relationship may be impaired or abolished in patients with intracranial mass lesions, brain trauma, cerebral vasospasm or increased cerebral elastance. Sedatives, analgetics, and anesthetics may induce major changes in cerebral blood flow, cerebral metabolism and intracranial pressure (ICP). The inadequate use of these drugs may aggravate the preexisting intracranial pathology and may worsen outcome. Thus it is important to understand the effects of sedatives, analgetics, and anaesthetics on intracranial hemodynamics and metabolism during physiological and pathological conditions. Hypnotics (barbiturates, etomidate, propofol), benzodiazepines, opioids (fentanyl, alfentanil, sufentanil) and alpha-2-adrenergic agonists (clonidine, dexmedetomidine) reduce cerebral blood flow. With ketamine, cerebral blood flow changes in a regionally specific fashion, with some territories showing increases and others showing decreases in cerebral blood flow. Cerebral metabolism is decreased during sedation and analgesia with hypnotics, benzodiazepines, and opioids, while infusion of ketamine produces stimulation as well as suppression of cerebral metabolism. This suggests that the changes in cerebral blood flow seen with these drugs occur secondary to their cerebral, metabolic effects. Alpha-2-adrenergic agonists produce no significant changes in cerebral metabolism. However, cerebral blood flow is decreased with clonidine or dexmedetomidine. This suggests uncoupling between cerebral metabolism and flow due to decreases in central catecholamine turnover. Hypnotics and benzodiazepines decrease ICP due to decreases in cerebral blood volume. However, these drugs may also decrease mean arterial blood pressure, which may result in a critical reduction in cerebral perfusion pressure. ICP remains unchanged with the use of opioids as long as mean arterial pressure is maintained constant. However, decreases in mean arterial pressure during infusion of opioids induce autoregulatory cerebral vasodilation, which in turn increases cerebral blood volume and ICP. Ketamine may increase ICP specifically in subjects with spontaneous ventilation. With mechanical hyperventilation and constant systemic hemodynamics, ketamine fails to increase ICP in most of the patients. Alpha-2-adrenergic agonists produce no significant changes in ICP, although there may be a transient decrease in ICP with lower doses.

Analgesics↗

PubMed1976