Shunt haemodynamics and extracorporeal dialysis: an electrical resistance network analysis

Abstract

A time-dependent resistance model is used to study haemodynamic aspects of haemodialysis treatment. In the first part of the paper one model circuit, consisting of a pressure source, upstream and downstream resistances and a branching resistance, is shown to represent the haemodynamics of any type of arteriovenous fistula (AVF). Simple algebraic relations are derived for the haemodynamic determinants of AVFS, including finger ischaemia and AVF-maturation. The second part of the paper analyses the influences of a two-needle extracorporeal dialysis (ECD) circuit on the systemic vascular haemodynamics. The main result of the analysis is that the ECD-circuit can be considered as virtually independent of the systemic circulation. Consequently the dialysis flow does not depend on systemic vascular determinants and there are no instantaneous changes in the systemic circulation after switching on the ECD circuit. The ECD flow at onset of AVF collapse is shown to be (slightly) larger than the undisturbed AVF flow. Hence, onset of collapse strongly depends on the systemic blood pressure and vascular resistances. It can be used diagnostically to assess AVF capacities. Optimisation of haemodialysis through the ECD circuit is predicted to be inefficient.

Hand Ischemia Associated With Dialysis Vascular Access: An Individualized Access Flow‐based Approach to Therapy

“…After this, the optimally developing fistula becomes relatively stable. However, its use‐life is characterized by slowly increasing blood flow , blood velocity and size over time.…”

“…Proximalization of the arterial inflow (PAI) has been used as a primary “preemptive” procedure to create a vascular access in patients judged to be at high risk for DASS based upon the idea that this would result in a successful hemodialysis access while mitigating the risk of DASS. This procedure using upper brachial or axillary arteries is in theory and in practice infrequently associated with distal ischemic events. As mentioned earlier, if the PRA is available, along with a nearby vein, such a “distalization” to a smaller inflow artery would be an ideal primary preemptive construction to avoid ischemia.…”

Steal phenomenon in radiocephalic arteriovenous fistula. In vitro haemodynamic and electrical resistance simulation studies

“…It was thought that such a model would be useful in understanding the alterations in the local haemodynamics, and explaining the conditions that lead to the development of arterial steal syndrome. Similar models have been proposed previously 13,14 but we have extended these to include the presence of a significant stenosis in the brachial, ulnar and radial arteries and also present the results of an experimental study to assess the applicability of the resistance model. The dimensions of the vessels in the forearm and the fistula flow vary over a relatively wide range in vivo.…”

Variable Pump Flow–Based Doppler Ultrasound Method

“…In 1984, van Gemert et al (22) proposed a two-needle extracorporeal dialysis circuit model to demonstrate the possible relationship between Qb and other hemodynamic parameters. He concluded that Qb has no instantaneous influence on vascular hemodynamics if Qb is less than Qa.…”