Improving Arteriovenous Fistula Patency (METTRO)

Second Generation Surveillance Techniques to Prevent Thrombosis and Increase Assisted Primary Patency in Native Arteriovenous Fistula. A Prospective Controlled Trial.

All vascular access guidelines recommend monitoring and surveillance protocols to prevent vascular access complications in hemodialysis units. However, in the case of second generation screening techniques which determine access blood flow measurement (QA), there is a huge controversy about it´s efficiency. Although multiple observational studies find a decrease in the thrombosis rate and an increased primary assisted patency survival related to the use of these techniques, a recently published meta-analysis find contradictory results in the randomized controlled trials, affirming that the measurement of QA is useless in grafts and questionable in native arteriovenous fistulae (AVF). We have designed a multicenter, prospective, open label, controlled, randomized trial, to prove the usefulness of the QA measurement using two complementary second generation techniques, Doppler ultrasound and Transonic dilution method, compared to the classical monitoring and surveillance methods. The primary endpoint will be a reduction in the thrombosis rate with an increased assisted primary patency survival, and a cost effectiveness economic analysis. As secondary endpoints we will analyze the impact over non-assisted primary patency survival and secondary patency survival.

Definition: Multicenter, prospective, open label, controlled, randomized trial, to prove the usefulness of the QA measurement using two complementary second generation techniques, Doppler ultrasound and Transonic dilution method, compared to the classical monitoring and surveillance methods. For Patient Registries: Clinical data repository (CDR) paper notebook will contain all baseline patient characteristics and the information related to vascular access. These data will be collected by the different investigators and reviewed and included in data base by the study´s monitor. This information will be included in a centralized computer database (SPSS 15.0 computer system) and encoded in order to preserve patients´ confidentiality.

Thrombosis, Arteriovenous fistulae, Hemodialysis, Doppler ultrasound, Vascular access blood flow, Surveillance

Classical evaluation of AVF includes: Vital sings and predialysis physical examination of AVF every dialysis session. Effective blood flow, venous pressure, arterial pressure, at the beginning and at the end of the dialysis session. Weekly ktv test using biosensors or monthly if using monocompartimental Daugirdas equation. Quarterly recirculation with urea method. Following Spanish Nephrology VA guidelines will be consider as alarm criteria: 1.25% Increased venous pressure. 2.25% Decreased pump blood flow. 3.0,2 ktv decreased compared with previous measurement. 4.> 10% recirculation using urea method. 5.Prolonged coagulation time or cannulation difficulties in 3 consecutive dialysis sessions. 6.Pathologic physical examination with any other criteria.

In addition to the classical surveillance and monitoring methods, in the experimental group Doppler ultrasound and transonic dilution method will be performed on a quarterly basis. In addition to the classical alarm criteria and derived from the results in Doppler ultrasound an transonic dilution method the following alarm criteria would also be considered in the experimental group: 25% or higher decreased in QA compared with previous measurement. QA lower than 500 ml/min. Stenotic area with a higher than 50% reduction of blood vessel lumen would be considered as alarm criteria only if it comes with a haemodynamic repercussion criteria defined as Peak systolic velocity (PSV) higher than 400 cm/sc, aliasing, or PSV ratio stenosis/pre-stenosis higher than 3.

Doppler ultrasound and transonic dilution method technique will be performed in the experimental group quarterly. QA will be measured by both techniques and haemodynamic repercussion stenosis will be evaluated by doppler ultrasound.

Effective blood flow, venous pressure, arterial pressure, at the beginning and at the end of the dialysis session

Weekly ktv measurement using biosensors. In patients who have been dialyzed in monitors with no biosensors, ktv will be measured monthly using monocompartimental Daugirdas equation

Improved primary patency rate in arteriovenous fistulae with the use of doppler ultrasound and transonic dilution method

Differences in assisted primary patency rates (thrombosis free access survival) in AVF between the two groups: control group in which classical monitoring and surveillance techniques are applied and experimental group in which Doppler ultrasound and transonic were performed every three months in addition to classical methods. Cost efficacy analysis in both groups will be done, measuring all vascular access (VA) related health care spending (VA hospitalization costs, central venous catheter (CVC) placements, surgeries and endovascular procedures will be recorded).

Compared non-assisted primary patency rates (intervention free access survival) and secondary patency rates (access survival until abandonment) between the two groups.

It will be evaluated the positive and negative predictive value of each second generation technique, doppler ultrasound and Transonic dilution method. The accuracy of these techniques will be compared to determine which one show more benefits detecting pathology of AVF.

There will be always two observers for each doppler ultrasound (same observers for same AVF). Differences among different quarterly measures in stable AVF will be evaluated, as well as the differences between the two observers in QA measurement.

It will be evaluated if there is any influence of age, body mass index, use of antiplatelet therapy, anticoagulant therapy or the use of pentoxifylline in the risk of thrombosis of AVF

Compared non-assisted primary patency rates (intervention free access survival) and secondary patency rates (access survival until abandonment) between the two groups.

It will be evaluated the positive and negative predictive value of each second generation technique, doppler ultrasound and Transonic dilution method. The accuracy of these techniques will be compared to determine which one show more benefits detecting pathology of AVF.

Compared non-assisted primary patency rates (intervention free access survival) and secondary patency rates (access survival until abandonment) between the two groups.

Inclusion Criteria: Informed consent signature. Age between 18 and 95 years old. Functioning native AVF. Patients with end stage renal disease (ESRD) undergoing hemodialysis program for at least three months. Exclusion Criteria: Coagulopathy or hemoglobinopathy of any cause. Hospitalization of any cause in the previous month. VA related complications or dysfunction in the previous three months.

Aragoncillo I, Abad S, Caldes S, Amezquita Y, Vega A, Cirugeda A, Moratilla C, Ibeas J, Roca-Tey R, Fernandez C, Macias N, Quiroga B, Blanco A, Villaverde M, Ruiz C, Martin B, Ruiz AM, Ampuero J, de Alvaro F, Lopez-Gomez JM. Adding access blood flow surveillance reduces thrombosis and improves arteriovenous fistula patency: a randomized controlled trial. J Vasc Access. 2017 Jul 14;18(4):352-358. doi: 10.5301/jva.5000700. Epub 2017 Apr 20.

Aragoncillo I, Amezquita Y, Caldes S, Abad S, Vega A, Cirugeda A, Moratilla C, Ibeas J, Roca-Tey R, Fernandez C, Quiroga B, Blanco A, Villaverde M, Ruiz C, Martin B, Ruiz AM, Ampuero J, Lopez-Gomez JM, de Alvaro F. The impact of access blood flow surveillance on reduction of thrombosis in native arteriovenous fistula: a randomized clinical trial. J Vasc Access. 2016 Jan-Feb;17(1):13-9. doi: 10.5301/jva.5000461. Epub 2015 Sep 18.