scholarly journals Incomplete Restoration of Homeostatic Shear Stress Within Arteriovenous Fistulae

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
Patrick M. McGah ◽  
Daniel F. Leotta ◽  
Kirk W. Beach ◽  
R. Eugene Zierler ◽  
Alberto Aliseda
Keyword(s):  
3D Ultrasound ◽  
Patient Specific ◽  
Shear Stresses ◽  
Arteriovenous Fistulae ◽  
Vessel Remodeling ◽  
Mechanical Homeostasis ◽  
Stage Renal Disease ◽  
End Stage ◽  
Hemodynamic Simulations

Arteriovenous fistulae are surgically created to provide adequate access for dialysis patients suffering from end-stage renal disease. It has long been hypothesized that the rapid blood vessel remodeling occurring after fistula creation is, in part, a process to restore the mechanical stresses to some preferred level, i.e., mechanical homeostasis. We present computational hemodynamic simulations in four patient-specific models of mature arteriovenous fistulae reconstructed from 3D ultrasound scans. Our results suggest that these mature fistulae have remodeled to return to ‘‘normal’’ shear stresses away from the anastomoses: about 1.0 Pa in the outflow veins and about 2.5 Pa in the inflow arteries. Large parts of the anastomoses were found to be under very high shear stresses >15 Pa, over most of the cardiac cycle. These results suggest that the remodeling process works toward restoring mechanical homeostasis in the fistulae, but that the process is limited or incomplete, even in mature fistulae, as evidenced by the elevated shear at or near the anastomoses. Based on the long term clinical viability of these dialysis accesses, we hypothesize that the elevated nonhomeostatic shear stresses in some portions of the vessels were not detrimental to fistula patency.

Effects of Wall Distensibility on the Numerical Simulation of Arteriovenous Fistulae

2013 ◽  
Author(s):  
Patrick M. McGah ◽  
Alberto Aliseda ◽  
Daniel F. Leotta ◽  
Kirk W. Beach
Keyword(s):  
Vascular Tissue ◽  
Peripheral Circulation ◽  
Shear Stresses ◽  
Dialysis Access ◽  
Arteriovenous Fistulae ◽  
Capillary Bed ◽  
One Year ◽  
Stage Renal Disease ◽  
End Stage ◽  
Hemodynamic Simulations

Arteriovenous fistulae are created surgically to provide an adequate access for dialysis in patients with End-Stage Renal Disease (ESRD). Producing an autogenous shunt linking an artery and a vein in the peripheral circulation bypasses the high resistance capillary bed in order to provide the necessary flow rates at sites easily accessible for dialysis. It has long been recognized that hemodynamics constitute the primary external influence on the remodeling process of anastomosed vascular tissue [1, 2]. The high flow rate, together with the exposure of the venous tissue to the high arterial pressure, leads to a rapid process of wall remodeling that may lead to a mature access or end in failure. Recent hemodynamic simulations [3, 4] have computed very high viscous wall shear stresses within dialysis access fistulae; Stresses >15 Pa have been reported. These are much higher than what is typically considered normal or homeostatic (i.e. ≈ 1–1.5 Pa). The abnormal stresses in the fistulae have been hypothesized to cause pathological venous remodeling (i.e. intimal hyperplasia) which causes stenoses and threatens fistula patency. Given the high failure rate of dialysis access sites (up to 50% require surgical revision within one year), understanding the dynamics of blood flow within the fistula is a necessary step in understanding remodeling, and ultimately, in improving clinical outcomes.

Incomplete Restoration of Homeostatic Shear Stress Within Arteriovenous Fistulae

2012 ◽  
Author(s):  
Patrick M. McGah ◽  
James J. Riley ◽  
Alberto Aliseda ◽  
Daniel F. Leotta ◽  
Kirk W. Beach
Keyword(s):  
Shear Stress ◽  
Peripheral Circulation ◽  
Shear Stresses ◽  
Dialysis Access ◽  
Venous Flow ◽  
Arteriovenous Fistulae ◽  
Flow Rates ◽  
Stage Renal Disease ◽  
End Stage ◽  
Low Shear

Arteriovenous fistulae are created surgically to provide an adequate access for dialysis in patients with End-Stage Renal Disease (ESRD). Producing an autogenous shunt linking an artery and a vein in the peripheral circulation bypasses the high resistance capillary bed in order to provide the necessary flow rates at sites easily accessible for dialysis. In successful fistulae, venous flow rates can easily exceed 1000 mL/min. It has long been recognized that the hemodynamics constitute the primary external influence on the remodeling process [1]; The high flow rate, together with the exposure of the venous tissue to the high arterial pressure, leads to a rapid process of wall remodeling that may end in a mature access or in failure. Recent hemodynamic simulations [2,3] have computed very high viscous wall shear stresses within fistulae; Stresses > 15Pa have been reported which are much greater than what is typically considered normal (i.e. homeostatic, ≈ 1Pa). Both sustained high shear and sustained low shear have been hypothesized to cause pathological venous remodeling (i.e. intimal hyperplasia) which causes stenoses and threatens fistula patency. The role of high vs. low shear stress in effecting patency remains unclear. Given the high failure rate of dialysis access sites (up to 50% require surgical revision within one year [4]), understanding the dynamics of blood flow within the fistula is a necessary step in understanding the remodeling, and ultimately, in improving clinical outcomes.

Frequency of Gastrointestinal Diseases in Patients with End-Stage Renal Disease Treated with Long Term Dialysis

2018 ◽  
Vol 2 (2) ◽  
pp. 105-112
Author(s):  
Lutfi Zylbeari ◽  
Zamira Bexheti ◽  
Gazmend Zylbeari ◽  
Ferizate Haxhirexha ◽  
Kastriot Haxhirexha
Keyword(s):  
Renal Disease ◽  
End Stage Renal Disease ◽  
Gastrointestinal Diseases ◽  
Stage Renal Disease ◽  
End Stage

scholarly journals Numerical computation of blood flow for a patient-specific hemodialysis shunt model

2021 ◽  
Author(s):  
Surabhi Rathore ◽  
Tomoki Uda ◽  
Viet Q. H. Huynh ◽  
Hiroshi Suito ◽  
Toshitaka Watanabe ◽  
...  
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Arteriovenous Shunt ◽  
Navier Stokes ◽  
Patient Specific ◽  
Stabilized Finite Element ◽  
Computed Tomography Scanning ◽  
Outflow Boundary ◽  
Stage Renal Disease ◽  
End Stage

AbstractHemodialysis procedure is usually advisable for end-stage renal disease patients. This study is aimed at computational investigation of hemodynamical characteristics in three-dimensional arteriovenous shunt for hemodialysis, for which computed tomography scanning and phase-contrast magnetic resonance imaging are used. Several hemodynamical characteristics are presented and discussed depending on the patient-specific morphology and flow conditions including regurgitating flow from the distal artery caused by the construction of the arteriovenous shunt. A simple backflow prevention technique at an outflow boundary is presented, with stabilized finite element approaches for incompressible Navier–Stokes equations.

scholarly journals Long-term risks after kidney donation: how do we inform potential donors? A survey from DESCARTES and EKITA transplantation working groups

2021 ◽  
Author(s):  
Geir Mjøen ◽  
Umberto Maggiore ◽  
Nicos Kessaris ◽  
Diederik Kimenai ◽  
Bruno Watschinger ◽  
...  
Keyword(s):  
Evaluation Process ◽  
Kidney Donation ◽  
Kidney Donors ◽  
Living Kidney Donors ◽  
Relative Risks ◽  
Written Information ◽  
The Difference ◽  
Stage Renal Disease ◽  
End Stage

Abstract Background Publications from the last decade have increased knowledge regarding long-term risks after kidney donation. We wanted to perform a survey to assess how transplant professionals in Europe inform potential kidney donors regarding long-term risks. The objectives of the survey were to determine how they inform donors and to what extent, and to evaluate the degree of variation. Methods All transplant professionals involved in the evaluation process were considered eligible, regardless of the type of profession. The survey was dispatched as a link to a web-based survey. The subjects included questions on demographics, the information policy of the respondent and the use of risk calculators, including the difference of relative and absolute risks and how the respondents themselves understood these risks. Results The main finding was a large variation in how often different long-term risks were discussed with the potential donors, i.e. from always to never. Eighty percent of respondents stated that they always discuss the risk of end-stage renal disease, while 56% of respondents stated that they always discuss the risk of preeclampsia. Twenty percent of respondents answered correctly regarding the relationship between absolute and relative risks for rare outcomes. Conclusions The use of written information and checklists should be encouraged. This may improve standardization regarding the information provided to potential living kidney donors in Europe. There is a need for information and education among European transplant professionals regarding long-term risks after kidney donation and how to interpret and present these risks.

Radiation protection perspective to recurrent medical imaging: what is known and what more is needed?

2021 ◽  
pp. 20210477
Author(s):  
Jenia Vassileva ◽  
Ola Holmberg
Keyword(s):  
Radiation Protection ◽  
Current Knowledge ◽  
Clinical History ◽  
Patient Specific ◽  
Individual Radiosensitivity ◽  
Dose Saving ◽  
End Stage ◽  
Future Work ◽  
Standardised Patient

This review summarises the current knowledge about recurrent radiological imaging and associated cumulative doses to patients. The recent conservative estimates are for around 0.9 million patients globally who cumulate radiation doses above 100 mSv, where evidence exists for cancer risk elevation. Around one in five is estimated to be under the age of 50. Recurrent imaging is used for managing various health conditions and chronic diseases such as malignancies, trauma, end-stage kidney disease, cardiovascular diseases, Crohn’s disease, urolithiasis, cystic pulmonary disease. More studies are needed from different parts of the world to understand the magnitude and appropriateness. The analysis identified areas of future work to improve radiation protection of individuals who are submitted to frequent imaging. These include access to dose saving imaging technologies; improved imaging strategies and appropriateness process; specific optimisation tailored to the clinical condition and patient habitus; wider utilisation of the automatic exposure monitoring systems with an integrated option for individual exposure tracking in standardised patient-specific risk metrics; improved training and communication. The integration of the clinical and exposure history data will support improved knowledge about radiation risks from low doses and individual radiosensitivity. The radiation protection framework will need to respond to the challenge of recurrent imaging and high individual doses. The radiation protection perspective complements the clinical perspective, and the risk to benefit analysis must account holistically for all incidental and long-term benefits and risks for patients, their clinical history and specific needs. This is a step toward the patient-centric health care.

scholarly journals Does a Supplemental Low-Protein Diet Decrease Mortality and Adverse Events After Commencing Dialysis? A Nationwide Cohort Study

Nutrients ◽  
2018 ◽  
Vol 10 (8) ◽  
pp. 1035 ◽  
Author(s):  
Chieh-Li Yen ◽  
Kun-Hua Tu ◽  
Ming-Shyan Lin ◽  
Su-Wei Chang ◽  
Pei-Chun Fan ◽  
...  
Keyword(s):  
Protein Diet ◽  
Low Protein Diet ◽  
Research Database ◽  
Negative Consequences ◽  
Term Survival ◽  
Low Protein ◽  
All Cause Mortality ◽  
Stage Renal Disease ◽  
End Stage

Background: A beneficial effect of a ketoanalogue-supplemented low-protein diet (sLPD) in postponing dialysis has been demonstrated in numerous previous studies. However, evidence regarding its effect on long-term survival is limited. Our study assessed the long-term outcomes of patients on an sLPD after commencing dialysis. Methods: This retrospective study examined patients with new-onset end-stage renal disease with permanent dialysis between 2001 and 2013, extracted from Taiwan’s National Health Insurance Research Database. Patients who received more than 3 months of sLPD treatment in the year preceding the start of dialysis were extracted. The outcomes studied were all-cause mortality, infection rate, and major cardiac and cerebrovascular events (MACCEs). Results: After propensity score matching, the sLPD group (n = 2607) showed a lower risk of all-cause mortality (23.1% vs. 27.6%, hazard ratio (HR) 0.77, 95% confidence interval (CI) 0.70–0.84), MACCEs (19.2% vs. 21.5%, HR 0.86, 95% CI 0.78–0.94), and infection-related death (9.9% vs. 12.5%, HR 0.76, 95% CI 0.67–0.87) than the non-sLPD group did. Conclusion: We found that sLPD treatment might be safe without long-term negative consequences after dialysis treatment.

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