A good vascular access (VA) is vital for hemodialysis (HD) patients. The start of HD with autologous arteriovenous fistula (AVF) means higher survival, lower sanitary costs and complications. The distal forearm AVF is known as the best option but not all patients are good candidates for this surgery, and there is a primary failure rate between 20 and 50% published in literature.

The choice of the optimal AVF for each patient is conditioned mainly by the anatomical and hemodynamic characteristics of the artery and the vein chosen to perform the anastomosis. These characteristics can be modified by performing physical exercise Some vascular access guidelines suggest the performance of isometric exercises in the pre and postoperative period of the AVF confection. However, there is very little data in literature on the possible efficacy of preoperative exercise, although small published observational studies point to an improvement in the venous and arterial caliber. Regarding the postoperative exercises, they do seem to improve maturation, however the degree of evidence in literature is low and there is no consensus on the exercise protocol to follow.

We present an open-label, multicenter, prospective, controlled and randomized study in order to evaluate the usefulness of preoperative isometric exercise (PIE) in pre-dialysis patients or in prevalent HD with indication of performing a new AVF. The randomization will be 1: 1, one group of patients will perform PIE for 8 weeks and the other group of patients will be a control group. The main purpose will be to evaluate if there is a lower rate of primary failure in the PIE group compared with control group.

RECRUITING PERIOD: 20 months.

FOLLOW UP: From the first preoperative assessment visit for AVF up to 3 months after its creation.

METHODS:

After signing the informed consent, patients will be randomized through a centralized computer program to one of two groups of patients, PIE group versus control group.

In both groups of patients, a first physical examination of upper arm extremities and an initial doppler ultrasound will be performed, evaluating the anatomical and hemodynamic characteristics of the arteries and veins of both arms. At that time, a first surgical option of AVF will be indicated.

In the PIE group, the patients will receive detailed information about the daily preoperative exercise protocol and they will perform this protocol for at least six and ideally more than eight weeks based on:

• Isometric exercise using hand-grip. This exercise consists of two sets of 30 hand-grip contractions with the hand of the upper arm candidate for AVF (in case of doubts about the most appropriate arm for AVF the exercise will be performed with both arms). The patient will rest one minute every 10 contractions and 5 minutes between both sets. The patient will repeat this protocol twice a day, morning and night (Approximately 15 minutes each session). The contraction intensity will start with half of the maximum force obtained by dynamometry and will be increased or decreased to be placed on an effort intensity 2-3 in the Borg scale.
• Isometric exercise using elastic bands. At noon the patient will perform a slow contraction session using elastic band with 20 slow repetitions with the arm in flexion and 20 repetitions with the arm in extension. (Total duration: less than 10 minutes) Clinical follow-up of these patients will be fortnightly to ensure that they perform the exercises correctly and to measure the force acquired through dynamometry. Likewise, brachial diameter and bicipital and tricipital skinfolds will be measured. In addition, they will be contacted by telephone once a week to assess compliance. Doppler ultrasonography will be performed at the initial visit, and at 4 and 8 week-visits (visits 1, 2 and 3). In the doppler ultrasound performed at 8 weeks, the final surgical indication will be given depending on the caliber of the vessels in the chosen arm. At the initial visit and at the 8-week visit, biological samples will be obtained to assess the parameters of nutrition and muscle mass and a bioimpedanciometry will be performed.

The date of surgery will be coordinated with anesthesia and peripheral vascular surgery services to program the intervention during the fortnight after the 8-week isometric exercise period (weeks 9-10). In prevalent HD patients with central venous catheter (CVC) presenting greater urgency of AVF, surgery will be scheduled between the 6 and 8 week of exercises.

Control group patients will follow the usual surgical waiting list protocol (Estimated 1,5-2 months). Baseline and preoperative ultrasonography will also be performed in these patients, in which it will be verified that there are no significant changes in vascular mapping (punctures sites, hematomas, etc.) and the indication of AVF performed in the initial visit will be confirmed. Dynamometry, bicipital and tricipital skinfolds measurement, brachial diameter, analytical parameters of nutrition and muscle mass and bioimpedanciometry will be performed both at the onset visit and at the preoperative visit. The only difference with PIE group is the 4 weeks follow-up ultrasound that will not be performed in control group.

After the AVF creation the maturation will be monitored with doppler ultrasound at 1, 6 and 12 weeks after the surgery (visits 4, 5 and 6) and the usual postoperative isometric exercise with ball contraction will be recommended to all patients. Follow-up will be completed three months after the surgical procedure, defining whether the AVF has matured or if there has been a primary failure.

FOLLOW-UP LOSSES:

• Abandonment or withdrawal of informed consent.
• Transplant.
• Change of dialysis technique.
• Transfer to another center.
• Exitus.

We will study if there is any correlation between nutritional-inflammatory status of the patients included in both groups and the AVF outcomes.

The nutritional-inflammatory status will be evaluated with clinical and biochemical parameters, including endothelial disfunction biomarkers.

Inclusion Criteria:

• Informed consent signature.
• Age between 18 and 89 years.
• Patients with advanced chronic kidney disease, stages IV-V, in pre-dialysis or prevalent HD patients, requiring new AVF.

Exclusion Criteria:

• Absence of adequate arteries and veins to allow autologous AVF. (The minimum gauges that will be considered in order to perform an autologous AVF are: artery caliber equal or greater than 1.6 mm and vein caliber equal or greater than 1,8 mm with a compressor).
• Diagnosis of coagulopathy or hemoglobinopathy of any cause.
• Patients who urgently need an AVF without the possibility of being 8 weeks on the surgical waiting list.
• Impossibility to perform the physical exercise protocol due to physical or mental disabilities or lack of social support.