Perfusion of the cerebral ventricular system in unanesthetized goats

1962 ◽  
Vol 203 (5) ◽  
pp. 763-774 ◽  
Author(s):  
J. R. Pappenheimer ◽  
S. R. Heisey ◽  
E. F. Jordan ◽  
J. deC. Downer
Keyword(s):  
Cerebrospinal Fluid ◽  
Steady State ◽  
Hydrostatic Pressure ◽  
Hydrodynamic Resistance ◽  
Nervous Control ◽  
System Composition ◽  
Bulk Absorption ◽  
Choroid Plexuses ◽  
Volume Characteristics ◽  
State Difference

Techniques have been devised for repeated perfusion of the ventriculocisternal system in chronically prepared, unanesthetized goats. The methods are designed for investigations of a) functional effects of prolonged changes of cerebrospinal fluid (CSF) composition and b) quantitative aspects of CSF formation and exchange of materials between CSF and blood. The present paper provides a technical background for subsequent papers dealing with specific problems. Goats tolerate perfusion rates of 1–3 ml/min at pressures adjustable between –10 and +30 cm H2O. Measurements are made of inflow rates, outflow rates, and concentrations of test materials entering and leaving the system. Composition of normal CSF has been determined and directions are given for preparation of sterile synthetic CSF. Brain weight is about 100 g and choroid plexuses 500 mg. CSF volume is 20–25 ml of which 8–12 ml is in the ventricles. Pressure-volume characteristics are described. Steady-state difference between inflow and outflow rates is a linear function of hydrostatic pressure; the slope is related to hydrodynamic resistance to bulk absorption. Preliminary observations are given to show effects of reduced Ca++ on nervous control of the cardiovascular system.

Resistance to Outflow of Cerebrospinal Fluid Determined by Bolus Injection Technique and Constant Rate Steady State Infusion in Humans

Neurosurgery ◽  
1985 ◽  
Vol 16 (3) ◽  
pp. 336-340 ◽  
Author(s):  
Michael Kosteljanetz
Keyword(s):  
Cerebrospinal Fluid ◽  
Steady State ◽  
Bolus Injection ◽  
Point Of View ◽  
Injection Technique ◽  
Communicating Hydrocephalus ◽  
Constant Rate ◽  
High Degree ◽  
Infusion Technique

Abstract Two methods for the determination of resistance to the outflow of cerebrospinal fluid, the bolus injection technique and the constant rate steady state infusion technique, were compared. Thirty-two patients with a variety of intracranial diseases (usually communicating hydrocephalus) were studied. There was a high degree of correlation between the resistance values obtained with the two methods, but values based on the bolus injection technique were systematically and statistically significantly lower than those obtained with the constant rate infusion test. From a practical point of view. both methods were found to be applicable in a clinical setting.

Exchange of inulin and dextran between blood and cerebrospinal fluid

1961 ◽  
Vol 201 (6) ◽  
pp. 1145-1148 ◽  
Author(s):  
Arthur R. Rothman ◽  
Emil J. Freireich ◽  
James R. Gaskins ◽  
Clifford S. Patlak ◽  
David P. Rall
Keyword(s):  
Cerebrospinal Fluid ◽  
Steady State ◽  
Venous System ◽  
Bulk Flow ◽  
Entry Rate ◽  
Important Means ◽  
Subarachnoid Spaces

C14-labeled inulin (mol. wt. 5,000) and C14-labeled dextran (mol. wt. 12,800 and 77,700) were studied for entry rate into CSF and steady state ratio of drug in cerebrospinal fluid (CSF) to drug in plasma, in nephrectomized dogs. For all three of these compounds the entry rates and steady state ratios were very similar. Exit rates of C14-inulin and C14-dextran (mol. wt. 77,700) were studied in nephrectomized and nonnephrectomized dogs. The exit rates were rapid and very similar for the two compounds. Acetazolamide increased the steady state ratio and decreased the exit rates significantly. These data suggest the presence of leaks in the blood CSF barrier of at least 60 A in diameter and indicate that bulk flow of CSF from the subarachnoid spaces to the venous system is an important means of exit of substances present in the CSF. Compounds which enter the CSF slowly fail to achieve diffusion equilibrium because of their relatively rapid exit by means of bulk flow.

Comparison of Fluconazole Pharmacokinetics in Serum, Aqueous Humor, Vitreous Humor, and Cerebrospinal Fluid Following a Single Dose and at Steady State

1998 ◽  
Vol 14 (5) ◽  
pp. 459-471 ◽  
Author(s):  
UMAR K. MIAN ◽  
MARTIN MAYERS ◽  
YOGENDER GARG ◽  
QING-FENG LIU ◽  
GIRARD NEWCOMER ◽  
...  
Keyword(s):  
Cerebrospinal Fluid ◽  
Single Dose ◽  
Steady State ◽  
Aqueous Humor ◽  
Vitreous Humor

Solutions for Non-Newtonian Flow Into Elliptical Openings

1991 ◽  
Vol 58 (3) ◽  
pp. 820-824 ◽  
Author(s):  
A. Bogobowicz ◽  
L. Rothenburg ◽  
M. B. Dusseault
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Steady State ◽  
Hydrostatic Pressure ◽  
Velocity Field ◽  
Velocity Fields ◽  
Newtonian Flow ◽  
Element Analysis ◽  
Elliptical Opening ◽  
Elliptical Coordinates

A semi-analytical solution for plane velocity fields describing steady-state incompressible flow of nonlinearly viscous fluid into an elliptical opening is presented. The flow is driven by hydrostatic pressure applied at infinity. The solution is obtained by minimizing the rate of energy dissipation on a sufficiently flexible incompressible velocity field in elliptical coordinates. The medium is described by a power creep law and solutions are obtained for a range of exponents and ellipse eccentricites. The obtained solutions compare favorably with results of finite element analysis.

Gradient moment nulling for steady-state free precession MR imaging of cerebrospinal fluid

1991 ◽  
Vol 18 (5) ◽  
pp. 1038-1044 ◽  
Author(s):  
Michael L. Wood ◽  
Yuval Zur ◽  
Leo J. Neuringer
Keyword(s):  
Cerebrospinal Fluid ◽  
Steady State ◽  
Mr Imaging ◽  
Steady State Free Precession ◽  
Free Precession

scholarly journals Test Results of a Polymer Radiator of MTZ-80 Tractor Cooling System

2020 ◽  
Vol 14 (1) ◽  
pp. 55-60
Author(s):  
O. N. Didmanidze ◽  
R. T. Khakimov ◽  
E. P. Parlyuk ◽  
N. A. Bol’shakov
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Cooling System ◽  
Operating Mode ◽  
Aerodynamic Characteristics ◽  
Operating Conditions ◽  
Hydrodynamic Resistance ◽  
Measuring Instruments ◽  
Research Areas ◽  
In Series

Global car manufacturers wish to increase the number of manufactured products, reduce their cost and labor input. The choice of research areas, design and technological developments in radiator construction is an extremely important and urgent task, due to the mass production of radiators for tractors and automobiles on the one hand, and the favorable development prospects of these interrelated industries, on the other. (Research purpose) To substantiate theoretically and experimentally the use of a combined cooling system containing both aluminum and polymeric water radiators and similarly liquid-oil heat exchangers based on the four principles listed above on automobiles and tractors. (Materials and methods) The authors performed bench tests using a special wind tunnel to study the thermal and aerodynamic characteristics of a prototype tractor radiator with a polyurethane core. After reaching the steady-state operating mode of the installation, the experimental values were determined for the control and measuring instruments. (Results and discussion) The authors carried out measurements of all parameters of both coolants in series at each steady-state operating mode of the bench. They obtained the main indicators dependences (reduced heat transfer, aerodynamic and hydraulic drag) of the heat exchanger, close to the operating conditions of the vehicles. (Conclusions) A prototype MTZ-80 radiator with a polyurethane core has great prospects as a future alternative radiator. An increase by 10-15 percent in the radiator heat transfer is possible by using aluminum fi ns on the surface of the polyurethane plate. A 15-20 percent reduction in hydrodynamic resistance is achieved by increasing the diameter of the capillary throughput in a polyurethane plate and the number of plates themselves in the radiator cell.

scholarly journals Levofloxacin Disposition in Cerebrospinal Fluid in Patients with External Ventriculostomy

2003 ◽  
Vol 47 (10) ◽  
pp. 3104-3108 ◽  
Author(s):  
Federico Pea ◽  
Federica Pavan ◽  
Ennio Nascimben ◽  
Claudio Benetton ◽  
Pier Giorgio Scotton ◽  
...  
Keyword(s):  
Cerebrospinal Fluid ◽  
Steady State ◽  
Bacterial Meningitis ◽  
Acute Bacterial Meningitis ◽  
Terminal Phase ◽  
Communicating Hydrocephalus ◽  
Synergistic Activity ◽  
Dosing Interval ◽  
Concentration Time ◽  
Meningeal Inflammation

ABSTRACT In vitro levofloxacin exhibits both potent or intermediate activity against most of the pathogens frequently responsible for acute bacterial meningitis and synergistic activity with some beta-lactams. Since levofloxacin was shown to penetrate the cerebrospinal fluid (CSF) during meningeal inflammation both in animals and in humans, the disposition of levofloxacin in CSF was studied in 10 inpatients with external ventriculostomy because of communicating hydrocephalus related to subarachnoid occlusion due to cerebral accidents who were treated with 500 mg of levofloxacin intravenously twice a day because of extracerebral infections. Plasma and CSF concentration-time profiles and pharmacokinetics were assessed at steady state. Plasma and CSF levofloxacin concentrations were analyzed by high-pressure liquid chromatography. The peak concentration of levofloxacin at steady state (C max ss)was 10.45 mg/liter in plasma and 4.06 mg/liter in CSF, respectively, with the ratio of the C max ss in CSF to the C max ss in plasma being 0.47. The areas under the concentration-time curves during the 12-h dosing interval (AUC0-τs) were 47.69 mg · h/liter for plasma and 33.42 mg · h/liter for CSF, with the ratio of the AUC0-τ for CSF to the AUC0-τ for plasma being 0.71. The terminal-phase half-life of levofloxacin in CSF was longer than that in plasma (7.02 ± 1.57 and 5.51 ± 1.36 h, respectively; P = 0.034). The ratio of the levofloxacin concentration in CSF to the concentration in plasma progressively increased with time, from 0.30 immediately after dosing to 0.99 at the end of the dosing interval. In the ventricular CSF of patients with uninflamed meninges, levofloxacin was shown to provide optimal exposure, which approximately corresponded to the level of exposure of the unbound drug in plasma. The findings provide support for trials of levofloxacin with twice-daily dosing in combination with a reference beta-lactam for the treatment of bacterial meningitis in adults. This cotreatment could be useful both for overcoming Streptococcus pneumoniae resistance and for enabling optimal exposure of the CSF to at least one antibacterial agent for the overall treatment period.

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