The passage of a diffusible indicator through a microvascular system.

The Aim: (1) To develop a mathematical model of the passage of a diffusible indicator through microcirculation based on a stochastic description of diffusion and flow; (2) To use Goresky transform of the dilution curves of the diffusible indicators for the estimation of the permeability of a tissue-capillary barrier.

The Method: We assume that there are two causes for flow to be stochastic: (a) All microvessels are divided between open and closed microvessels. There exists random exchange between the two groups.

Hemodynamic recovery after hypovolemic shock with lactated Ringer's and keratin resuscitation fluid (KRF), a novel colloid.

Death after severe hemorrhage remains an important cause of mortality in people under 50 years of age. Keratin resuscitation fluid (KRF) is a novel resuscitation solution made from keratin protein that may restore cardiovascular stability. This postulate was tested in rats that were exsanguinated to 40% of their blood volume.

Stochasticity of flow through microcirculation as a regulator of oxygen delivery.

Objective: Observations of microcirculation reveal that the blood flow is subject to interruptions and resumptions. Accepting that blood randomly stops and resumes, one can show that the randomness could be a powerful means to match oxygen delivery with oxygen demand.

Method: The ability of the randomness to regulate oxygen delivery is based on two suppositions: (a) the probability for flow to stop does not depend on the time of uninterrupted flow, thus the number of interruptions of flow follows a Poisson distribution; (b) the probability to resume the flow does not depend on the time for flow being interrupted; meaning that time spent by erythrocytes at rest follows an exponential distribution.

Theory and in vitro validation of a new extracorporeal arteriovenous loop approach for hemodynamic assessment in pediatric and neonatal intensive care unit patients.

Objectives: No simple method exists for repeatedly measuring cardiac output in intensive care pediatric and neonatal patients. The purpose of this study is to present the theory and examine the in vitro accuracy of a new ultrasound dilution cardiac output measurement technology in which an extracorporeal arteriovenous tubing loop is inserted between existing arterial and venous catheters.

Design: Laboratory experiments.

Determining lung water volume in stable hemodialysis patients.

Lung water (LW) reflects the water content of the lung interstitium. Because hemodialysis patients have expanded total body water (TBW) they may also have increased LW. Hypertonic saline promotes a flux of water from lung to blood, which is measured by ultrasound flow probes on hemodialysis tubing.

Regulation of oxygen consumption by vasomotion.

Objective: To describe a stochastic model of the variability and heterogeneity of blood flow through the microcirculation, and to show the ability of vasomotion to vary oxygen consumption at a steady blood flow.

Methods: The description of vasomotion is based on whether each microvessel is open for blood flow or closed. Over a unit time period, let alpha be the probability that a given vessel is open and will remain open, beta be the probability that an open vessel will close, nu be the probability that a closed vessel will remain closed, and mu be the probability that a closed vessel will become open.

Heart blood volume by dilution in patients on hemodialysis.

Cardiomegaly and accompanying complications contribute to morbidity and mortality in patients on hemodialysis. Our objective is to provide a measure of heart blood volume from data collected during routine measurement of cardiac output during hemodialysis. A heart model based upon the probability of transfer between chambers during a cardiac cycle generates both the distribution of transit times (dilution curve) and the blood volumes in the chambers of the heart.

[Methods of cardiac output determination during extracorporeal detoxication].

Two new methods of determining the cardiac output (CO) in extracorporeal detoxication (ECD) by thermal dilution were verified. The CO values, determined by the dilution of electrical impedance indicators (COimp) and by COimp thermal dilution (COtd), were compared within 31 matched analysis in 20 patients. The correlation coefficient: r = 0.

Vasomotion model explanation for urea rebound.

Urea rebound after hemodialysis is generally attributed to urea entering the circulation from poorly perfused tissue and/or entering from regions with low membrane permeability for urea. Another explanation for rebound is based on disorders in the microcirculation, connected with the phenomenon of vasomotion, i.e.

Use of a catheter-based system to measure blood flow in hemodialysis grafts during angioplasty procedures.

Purpose: The goals of this investigation were to evaluate the accuracy and reliability of the Angioflow meter system with use of in vitro and in vivo methods and to compare it to the standard Transonics HD01 system in a clinical setting.

Materials And Methods: The Angioflow meter system consists of a 6-F endovascular catheter and a laptop computer containing proprietary software for this application. Bench-top testing with use of a flow model was performed to determine the accuracy of the Angioflow meter system.

In vivo measurement of hemodialyzer fiber bundle volume: theory and validation.

Background: Fiber bundle volume (FBV), the space within the blood compartment of hollow fiber dialyzers, may decrease during treatment due to clotting. The clots may be flushed out of the dialyzer prior to measurements of FBV by dialyzer reprocessing equipment and a significant drop in FBV during the session may go unrecognized.

Methods: FBV was measured (1) from the transit time of a saline bolus passing through the dialyzer as recorded by ultrasound dilution sensors placed on the arterial and venous blood lines; (2) from the change in blood concentration induced by a step change in the rate of ultrafiltration as recorded by the venous sensor.

Monitoring of cardiac function in patients with a left ventricle assist device.

In complex therapy of acute or chronic cardiac failure, the use of valve-free centrifugal pumps or artificial heart ventricles takes place. In these cases, simultaneous monitoring of cardiac and pump performance is very important. In this study, an ultrasound dilution method based on the registration of two dilution curves after intravenous injection of isotonic and hypertonic sodium solution was developed.

Volume of extravascular lung fluid determined by blood ultrasound velocity and electrical impedance dilution.

A hypertonic sodium chloride bolus passing through the lung has a sound velocity transient that is biphasic when it reaches the carotid artery. This transient is compatible with water moving into the hypertonic bolus from the lung parenchyma, thereby leaving the lung parenchyma hypertonic. Subsequently, as the bolus leaves the lung vasculature, water passes from the blood into the tissue to return the lung tonicity to baseline, giving a moment when net movement is zero, an instant of osmotic equilibrium.

Use of an extracorporeal arteriovenous tubing loop to measure cardiac output in intensive care unit patients by ultrasound velocity dilution.

Thermodilution cardiac output (CO) measurement requires heart catheterization and is known as a risk factor. The existing cannula in the radial artery in intensive care unit (ICU) patients can be used to measure CO by ultrasound dilution (COus). An arteriovenous shunt between the radial artery and cubital vein was created using a 25 cm tubing loop.

[The determination of cardiac output by the dilution of ultrasonic blood density].

The authors propose assessing cardiac output (CO) by diluting the blood ultrasonic properties. For measuring CO, the peripheral artery and vein were connected with a catheter, and ultrasonic flowmetric pickup was attached to the shunt. Indicator (0.

Simultaneous separate assessment of the cardiac and LVAD output.

The electroimpedance indicators' dilution (EIID) technique was used to study the possibility of a simultaneous separate assessment of the biological heart and LVAD performance in the position of LVB. The experimental part of the research was performed on 5 dogs; an artificial ventricle of the pulsing type (USA) with cusps was used as a pump. The clinical part of the work was conducted on 5 patients after open-heart surgery who had the clinical picture of postcardiotomy cardiogenic shock; a centrifugal pump "Biopump" (Medtronic, USA) was used.

[Dynamics of the content of the pulmonary extravascular fluid during extracorporeal detoxication in critical state patients].

Time course of the content of interstitial, cellular, and total fluid in the lungs, of plasma osmolality and sodium concentration was studied in 20 patients with acute renal failure after repair surgery on the heart, thoracic and abdominal organs. Water balance of the lungs was studied by dissolution of electroimpedance indicators before and after removal of 2000-2500 ml of ultrafiltrate. Ultrafiltration of the blood in the course of hemodialysis (group 1) did not lead to a reliable reduction of the volume of intravascular fluid, whereas in group 2 a reliable reduction of the volume of interstitial fluid of the lungs by 34% and of the total liquid volume of the lungs by 29% occurred in the course of hemofiltration.

[The electrical impedance indicator dilution method in studying the basic hemodynamic parameters during dialysis].

The procedure for measuring cardiac output and circulating blood volume is based on blood ability to modify its electrical conductance due to the amount of introduced ions (0.9% sodium chloride solution) or undissociated molecules (5% glucose solution). The cardiac output and circulating blood volume were calculated after measuring an area under the electrical impedance indicator dilution curve using the given formulas.

[The use of a vitamin and metabolite complex for correcting the disorders in systemic and organ hemodynamics during liver resection under conditions of acute blood loss].

The efficacy of some infusion media, vitamins, and metabolites in resection of the liver in acute blood loss was studied in experiments on dogs. Inclusion of vitamins B1, B2, and B6, lipoic acid, calcium pantothenate, nicotinamide, solution of alpha-glutamate and gamma-aminobutyric acid (aminalone) in the infusion led to a sharp increase of myocardial contractility, increase of cardiac output and total hepatic blood flow, normalization of biochemical blood values, and restoration of the activity of hepatocyte enzymes.

[Possibilities of the method of dilution of electro-impedance indicators in the assessment of volume dynamics of extravascular lung fluid in intensive care and resuscitation units].

The possibility of using impedance plethysmography to assess changes in the volume of the extravascular lung fluid in intensive therapy and resuscitation patients is discussed. Changes in the volume of the fluid during extracorporeal detoxication are analysed. A correlation was found between these changes and lung distensibility (r = -0.

[Study of parameters of central hemodynamics in patients during hemodialysis].

The article discusses the results of study of the cardiac output (CO) and circulation blood volume (CBV) in patients at the beginning and end of hemodialysis. The dynamics of changes of these parameters during hemodialysis was studied in 31 patients (42 sessions). The CO and CBV reduced significantly.