Constant Blood Flow during Single-Needle Dialysis is Unnecessary

1993 ◽  
Vol 16 (7) ◽  
pp. 505-509 ◽  
Author(s):  
H.D. Polaschegg ◽  
R. Wojke
Keyword(s):  
Blood Flow ◽  
Vascular Access ◽  
Pulsatile Flow ◽  
Tidal Flow ◽  
Constant Flow ◽  
Pulsatile Blood Flow ◽  
Flow Rates ◽  
Flow Through ◽  
Optimal Efficiency

Single-needle (SN) dialysis employs tidal blood flow at the point of vascular access. The simplest SN systems convert this tidal flow to a pulsatile flow in the dialyser. It has been assumed that constant flow through the dialyser is necessary for optimal efficiency. Therefore SN blood circuits are designed to smooth the pulsatile flow in the dialyser to a relatively constant flow. This increases the complexity and cost of the SN system. In order to test the hypothesis that pulsatile flow results in lower clearances than constant flow, we performed measurements of clearance in vitro using pulsatile blood flow at time-averaged rates of 50-250 ml/min and tidal volumes 200-100 ml/min. These were compared with clearances using constant blood flow at the same rates. At all flow rates and at tidal volumes up to 50 ml, the clearance measurements obtained during pulsatile flow were identical to those obtained during constant flow.

Myocardial Protection during Coronary Angioplasty with Autoperfusion and Forced Perfusion: An in vitro comparison

1994 ◽  
Vol 17 (2) ◽  
pp. 83-87 ◽  
Author(s):  
E.D. De Muinck ◽  
B.J. Verkerke ◽  
G. Rakhorst ◽  
K.I. Lie
Keyword(s):  
Blood Flow ◽  
Coronary Angioplasty ◽  
Myocardial Protection ◽  
Coronary Perfusion ◽  
Mean Flow ◽  
Perfusion Pump ◽  
Flow Rates ◽  
Balloon Catheters ◽  
Flow Through

During coronary angioplasty, perfusion distal to the inflated angioplasty balloon can be maintained with autoperfusion balloon catheters and coronary perfusion pumps. The blood flow rates through the autoperfusion balloon catheters and the flow rates achieved with a perfusion pump were compared in vitro with fresh human blood at 37° C. In a specially designed system, blood flow rates through Stack™ autoperfusion balloon catheters were measured at 40, 60 and 80 mmHg continuous pressure. In another system, driving pressures were measured during perfusion with the pump, through a specially designed forced perfusion catheter at 20, 40 and 60 ml/min flow. The pressure applied in the autoperfusion experiments was converted into atmospheres (atm) to facilitate comparison with the driving pressures measured during pumping (1 mmHg = 1.316 × 10−3 atm). Mean flow rates through the autoperfusion balloon catheters were: 46 ml/min at 0.05 atm, 66 ml/min at 0.09 atm and 75 ml/min at 0.1 atm. Mean pressures during pumping were: 1.8 atm at 20 ml/min, 3.5 atm at 40 ml/min, 5 atm at 60 ml/min. Due to the phasic nature of coronary blood flow, the flow through autoperfusion balloons is generally lower than the minimum required for adequate myocardial protection (= 60 ml/min). Thus, autoperfusion balloon catheters are simpler and cheaper devices than perfusion pumps, but generally they are not able to provide adequate myocardial protection.

Relation between intestinal blood flow and oxygen uptake

1982 ◽  
Vol 242 (3) ◽  
pp. G202-G208 ◽  
Author(s):  
P. R. Kvietys ◽  
D. N. Granger
Keyword(s):  
Blood Flow ◽  
Oxygen Uptake ◽  
Perfusion Pressure ◽  
Constant Flow ◽  
Flow Conditions ◽  
Venous Outflow ◽  
Flow Rates ◽  
Dose Dependent ◽  
Oxygen Difference

In autoperfused and pump-perfused preparations of canine ileum, arterial pressure, venous outflow pressure, blood flow, and arteriovenous oxygen difference were measured while blood flow was altered either mechanically or by graded intra-arterial infusions of isoproterenol, adenosine, or 2,4-dinitrophenol. In pump-perfused preparations, mechanical alterations in blood flow resulted in opposite changes in arteriovenous oxygen difference, so that ileal oxygen uptake was independent of blood flow over the range of 30-140 ml.min-1.100 g-1. Only at flow rates below 30 ml.min-1.100 g-1 was oxygen uptake dependent on blood flow. Isoproterenol, adenosine, and dinitrophenol produced dose-dependent increases in blood flow under free-flow conditions and decreases in perfusion pressure under constant-flow conditions. Ileal oxygen uptake was not affected by isoproterenol, decreased by adenosine, and increased by dinitrophenol. The effects of these drugs on intestinal oxygen uptake are in accord with their effects on oxygen consumption in vitro. These results suggest that vasodilators will not alter intestinal oxygen uptake in autoperfused preparations in which oxygen uptake is independent of blood flow, unless they exert an effect on oxidative metabolism.

scholarly journals A Simple Transient Poiseuille-Based Approach to Mimic the Womersley Function and to Model Pulsatile Blood Flow

Dynamics ◽  
2021 ◽  
Vol 1 (1) ◽  
pp. 9-17
Author(s):  
Andrea Natale Impiombato ◽  
Giorgio La Civita ◽  
Francesco Orlandi ◽  
Flavia Schwarz Franceschini Zinani ◽  
Luiz Alberto Oliveira Rocha ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Blood Flow ◽  
Boundary Conditions ◽  
Quadratic Function ◽  
Pulsatile Blood Flow ◽  
Flow Through ◽  
Simplified Analysis ◽  
Function Models ◽  
Flow Reversals

As it is known, the Womersley function models velocity as a function of radius and time. It has been widely used to simulate the pulsatile blood flow through circular ducts. In this context, the present study is focused on the introduction of a simple function as an approximation of the Womersley function in order to evaluate its accuracy. This approximation consists of a simple quadratic function, suitable to be implemented in most commercial and non-commercial computational fluid dynamics codes, without the aid of external mathematical libraries. The Womersley function and the new function have been implemented here as boundary conditions in OpenFOAM ESI software (v.1906). The discrepancy between the obtained results proved to be within 0.7%, which fully validates the calculation approach implemented here. This approach is valid when a simplified analysis of the system is pointed out, in which flow reversals are not contemplated.

scholarly journals Characteristics of Pulsatile Blood Flow Through 3-D Geometry of Arterial Stenosis

2015 ◽  
Vol 105 ◽  
pp. 877-884 ◽  
Author(s):  
Khairuzzaman Mamun ◽  
Most. Nasrin Akhter ◽  
Md. Shirazul Hoque Mollah ◽  
Md. Abu Naim Sheikh ◽  
Mohammad Ali
Keyword(s):  
Blood Flow ◽  
Arterial Stenosis ◽  
Pulsatile Blood Flow ◽  
Flow Through

scholarly journals In vivo / in vitro Correlation of Pharmacokinetics of Gentamicin, Vancomycin, Teicoplanin and Doripenem in a Bovine Blood Hemodialysis Model

2021 ◽  
Vol 12 ◽  
Author(s):  
M G Vossen ◽  
S Pferschy ◽  
C Milacek ◽  
M Haidinger ◽  
Mario Karolyi ◽  
...  
Keyword(s):  
Blood Flow ◽  
Renal Replacement Therapy ◽  
Protein Binding ◽  
Replacement Therapy ◽  
Flow Rate ◽  
Blood Flow Rate ◽  
Bovine Blood ◽  
Flow Rates ◽  
Dialysate Flow Rate

Background: Elimination of a drug during renal replacement therapy is not only dependent on flow rates, molecular size and protein binding, but is often influenced by difficult to predict drug membrane interactions. In vitro models allow for extensive profiling of drug clearance using a wide array of hemofilters and flow rates. We present a bovine blood based in vitro pharmacokinetic model for intermittent renal replacement therapy.Methods: Four different drugs were analyzed: gentamicin, doripenem, vancomicin and teicoplanin. The investigated drug was added to a bovine blood reservoir connected to a hemodialysis circuit. In total seven hemofilter models were analyzed using commonly employed flow rates. Pre-filter, post-filter and dialysate samples were drawn, plasmaseparated and analyzed using turbidimetric assays or HPLC. Protein binding of doripenem and vancomycin was measured in bovine plasma and compared to previously published values for human plasma.Results: Clearance values were heavily impacted by choice of membrane material and surface as well as by dialysis parameters such as blood flow rate. Gentamicin clearance ranged from a minimum of 90.12 ml/min in a Baxter CAHP-170 diacetate hemofilter up to a maximum of 187.90 ml/min in a Fresenius medical company Fx80 polysulfone model (blood flow rate 400 ml/min, dialysate flow rate 800 ml/min). Clearance of Gentamicin vs Vancomicin over the F80s hemofilter model using the same flow rates was 137.62 mL vs 103.25 ml/min. Doripenem clearance with the Fx80 was 141.25 ml/min.Conclusion: Clearance values corresponded very well to previously published data from clinical pharmacokinetic trials. In conjunction with in silico pharmacometric models. This model will allow precise dosing recommendations without the need of large scale clinical trials.

Role of transmural pressure in local regulation of blood flow through kidney

1965 ◽  
Vol 208 (5) ◽  
pp. 825-831 ◽  
Author(s):  
F. J. Haddy ◽  
J. B. Scott
Keyword(s):  
Blood Flow ◽  
Renal Artery ◽  
Transmural Pressure ◽  
Constant Flow ◽  
Tissue Pressure ◽  
Local Regulation ◽  
Artery Pressure ◽  
Flow Through ◽  
Response To Change ◽  
Renal Vascular

In the kidney of the anesthetized dog, the pressure in an occluded hilar lymphatic vessel was used as an index of tissue pressure. While elevation of renal vein pressure produced a large rise in lymphatic pressure, reduction of renal artery pressure had little effect. Similarly, while elevation of vein pressure at constant flow produced an almost equal rise in lymphatic pressure, large changes in blood flow and hence artery pressure had little effect, despite evidence of local regulation of resistance. Intra-arterial injection of vasoactive agents at constant flow, which produced large changes in renal artery pressure, had little effect on lymphatic pressure. Sudden transient increase in renal blood flow sometimes produced changes in perfusion pressure which could have resulted from active constriction subsequent to rise in transmural pressure. These findings provide little support for the tissue pressure theory of autoregulation but suggest that tissue pressure does participate in the vascular response to elevated vein pressure. The study also provides some evidence for a vascular myogenic response to change in renal vascular transmural pressure.

scholarly journals Effect of Intermittency on Pulsatile Blood Flow through a Stenosed Tube.

1999 ◽  
Vol 65 (630) ◽  
pp. 690-697
Author(s):  
Yoshiyuki WAKI ◽  
Takuji ISHIKAWA ◽  
Shuzo OSHIMA ◽  
Ryuichiro YAMANE ◽  
Motoharu HASEGAWA
Keyword(s):  
Blood Flow ◽  
Pulsatile Blood Flow ◽  
Flow Through

CFD Analysis Comparing Steady Flow and Pulsatile Flow Through the Aorta and its Main Branches

2016 ◽  
Author(s):  
John D. Martin
Keyword(s):  
Blood Flow ◽  
Steady Flow ◽  
Pulsatile Flow ◽  
Close Association ◽  
Beating Heart ◽  
Pressure Data ◽  
Heart Model ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Through ◽  
Very High

A computational fluid dynamics (CFD) study has been done comparing pulsatile and non-pulsatile blood flow through the aortic arch and its main branches. The pulsatile flow was to mimic the blood flow due to a beating heart and the non-pulsatile or steady flow was to mimic cardiopulmonary bypass (CPB). The purpose of the study was too narrow in on possible reasons CPB may contribute to the development of atherosclerosis. The main focus of the study was to look at the wall shear stress (WSS) values due to their close association with the development of atherosclerosis. In addition velocity and pressure data were also analyzed. The results of this study showed a stark contrast between the WSS values between the CPB model and the beating heart model. The CPB model did not have any points of oscillating WSS combined with the fact that there were regions of very high and very low constant WSS values in comparison with the beating heart analysis suggests that there may be potential for atherosclerotic development or plaque buildup within the artery. The beating heart model showed a range of WSS values within the aorta that were much lower overall compared with the CPB model.

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