Clinical Kidney Journal, 2021, vol. 14, no. 2, 688–695 doi: 10.1093/ckj/sfz194 Advance Access Publication Date: 5 February 2020 Original Article ORIGINAL ARTICLE Upper limb isometric exercise protocolled programme and arteriovenous fistula maturation process Irati Tapia González1,2,3, Vicent Esteve Simó1,2, Sara Iban ~ ez Pallares1,4, Fátima Moreno Guzman2, Miquel Fulquet Nicolás2, Verónica Duarte Gallego2, Anna Saurina Solé2, Mónica Pou Potau2, Montserrat Yeste Campos4 and Manel Ramı́rez de Arellano Serna2 1 Funtional Unit Vascular Access, Nephrology Department, Consorci Sanitari Terrassa, Barcelona, Spain, 2 Nephrology Department, Consorci Sanitari Terrassa, Barcelona, Spain, 3Department of Medicine, Universitat Autónoma de Barcelona, Barcelona, Spain and 4Vascular Surgery Department, Consorci Sanitari Terrassa, Barcelona, Spain Correspondence to: Irati Tapia González; E-mail: ITapiaG@cst.cat ABSTRACT Introduction. Arteriovenous fistula (AVF) is the gold standard for vascular access (VA) for end-stage chronic kidney disease (CKD) patients. Post-operative exercises may help to improve maturation. Nevertheless, scarce scientific evidence has been reported about their utility to date. Our objective was to assess the effect of a post-operative isometric exercise programme on native VA maturation in patients with stage 5–5D CKD. Methods. We performed a 24-month prospective study. After surgery, patients were randomized to the isometric exercise group (EG) or control group (CG). An isometric exercise protocolled programme was performed in the EG. The CG received usual care. Demographic data, muscle strength using a hand-grip (HG) dynamometer, main Doppler ultrasound (DUS) measurements, clinical and DUS maturation and VA complications were assessed at 4 and 8 weeks post-operatively. Results. For 60 sixty patients (30 in the EG), demographic data and HG and DUS measurements at baseline were similar. A significant increase in HG was observed only in the EG at the end of the study (20.7 6 8.1 versus 25.1 6 10.3 kg, P ¼ 0.001). The EG obtained the highest clinical maturation at 4 (CG 33.3% versus EG 70%, P ¼ 0.009) and 8 weeks (CG 33.3% versus EG 76.7%, P ¼ 0.002). Similarly, DUS maturation was better in the EG at 4 (CG 40% versus EG 80%, P ¼ 0.003) and 8 weeks (CG 43.3% versus EG 83.3%, P ¼ 0.003) and remained so in the EG for both distal and proximal VA territories for all these periods. Conclusions. The upper limb isometric exercise protocolled programme improved clinical and DUS maturation in our patients in both the distal and proximal VA territories. Further studies are required to support these results. Keywords: chronic kidney disease, isometric exercise, maturation, vascular access Received: 6.9.2019; Editorial decision: 16.12.2019 C The Author(s) 2020. Published by Oxford University Press on behalf of ERA-EDTA. V This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/ licenses/by-nc/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact journals.permissions@oup.com 688 Isometric exercises and maturation process | 689 INTRODUCTION Physical examination, ultrasound parameters and maturation criteria Autologous arteriovenous fistula (AVF) is the preferred choice for vascular access (VA) in patients with chronic kidney disease All patients underwent a protocol-based physical examination (CKD) undergoing a haemodialysis (HD) programme [1–5], due and universal preoperative ultrasound mapping. The physical to its increased rate of permeability and reduced rates of com- examination consisted of a visual assessment of both arms, the plications and hospitalizations [6–11]. The maturation process venous system was explored by means of venous palpation for VA is one of the most important factors affecting the subse- both with and without a tourniquet and the quality of arterial quent correct functioning of the VA given that an immature VA pulses was determined by means of digital palpation, including leads to more complications and, as a result, can reduce the the Allen test. likelihood of VA survival [12–14]. Ultrasound examination was carried out by the Functional Both the current guidelines from the Spanish Nephrology Unit Vascular Access team, following the same protocol and us- Society relating to VA for haemodialysis [5] and the guidelines ing the same ultrasound device: a Sonoline G40 ultrasound sys- from the Kidney Disease Outcomes Quality Initiative recom- tem (Siemens Medical Solutions, Mountain View, CA, USA). The ultrasound data analysed in both arms for each patient were mend that patients carry out regular isometric exercises, in the diameters (mm) of the radial artery (RA) and humeral artery both the pre-intervention and post-intervention periods, as pre- (HA), the cephalic vein (CV) diameters in the lower and upper ventative measures with respect to the development of AVFs arm, the diameter and depth of the basilic vein (BV), as well as and the occurrence of complications [7, 15]. the permeability and continuity of all the vessels. Similarly, In recent years, some studies have suggested that isometric peak systolic velocities (PSVs; in cm/s) in the RA and HA, the re- physical exercise of the arms can serve as a strategy to acceler- sistance index (RI) of the RA following the reactive hyperaemia ate the maturation of AVFs [16–19]. However, the evidence test and the flow through the HA were recorded. available on the role of physical exercise in the post-operative In accordance with the current Clinical Guidelines for period for improvement in the maturation or survival of autolo- Vascular Access of the Spanish Nephrology Society, the non- gous AVFs remains limited. dominant arm was preferentially selected and a distal area cho- The aim of our study was to evaluate the effects of a fixed sen for creation of the AVF [5]. All AVFs were created by the programme of isometric physical exercise on the maturation of same team from the Vascular Surgery section within our insti- autologous AVFs in patients with CKD stages 5–5D. tution (with extensive experience in this field) following ex- haustive clinical and ultrasound assessment and using similar MATERIALS AND METHODS AVF procedures. The ultrasound measurements considered to be suitable for a distal AVF were CV diameter in the lower arm Between November 2015 and December 2017, a prospective, >2 mm or >2.5 mm with tourniquet, RA diameter >1.5 mm, PSV randomized, single-centre 24-month study was performed, ap- >50 cm/s and a reactive hyperaemia test with an RI <0.7. proved by the ethics committee of our institution and in accor- Similarly, measurements considered suitable for a proximal dance with the standards of the Declaration of Helsinki, in order AVF were HA diameter >2.5 mm, PSV >50 cm/s, CV diameter at to evaluate the effects of an isometric exercise programme car- the elbow >2.5 mm and BV diameter >2.5 mm [5]. All of the ried out in the post-operative period on the maturation of autol- measurements (pre-operatively and at 4 and 8 weeks) were car- ogous AVFs in patients with CKD stages 5–5D. ried out at the same sites (HA 3 cm from the bifurcation of the The inclusion criteria established were obtaining informed artery and veins 3 cm proximal to the arteriovenous anastomo- consent, age >18 years, CKD stage 5 or 5D, candidate for autolo- sis). The AVF flow was estimated by means of flow in the HA as gous AVF for haemodialysis (HD) in upper limbs and preserved the method with the best correlation [23, 24]. Local anaesthesia capacity for understanding. Patients excluded were those that was usually used, except for brachial basilic AVF with superfici- had a prior autologous AVF in the same arm, were not candi- alization, which was performed under regional blockade. The dates for autologous AVFs, had suffered a cardiovascular event AVF localization recorded was distal (radiocephalic) and proxi- in the last 3 months, had limited osteoarticular pathology and mal (brachiocephalic or brachiobasilic, with or without superfi- those that did not give written, informed consent. cialization) or both with side-to-end anastomosis. Clinical and ultrasound maturation were assessed at 4 and Data on demographics, biochemistry, nutrition and 8 weeks post-intervention. The criteria for clinical maturation muscle strength were established as the presence of a palpable thrill, visible vein and a straight line >10 cm. The ultrasound maturation criteria The demographic parameters included age, sex, renal aetiology, were depth <0.6 cm from the skin, outflow vein with a diameter Charlson Comorbidity Index and traditional cardiovascular risk >6 mm and HA flow rate >600 mL/min [5]. Any AVF complica- factors. Similarly, data on the main nutritional and biochemical tions were also recorded (stenosis, thrombosis, haematoma, parameters were collected. pseudoaneurysm or VA steal syndrome). Muscle strength of the AVF limb was evaluated at the start of the study and at 4 and 8 weeks post-intervention. An adapted mechanical hand-grip dynamometer was used to carry out Allocation to groups and isometric physical exercise these measurements. The muscle strength in the arm on which protocol the intervention was carried out, estimated in kilograms, was During the post-operative period, patients were randomized us- measured using a pre-published protocol [20–22]. An average ing a centralized information technology–based randomization was calculated on the basis of three consecutive measurements tool and allocated to two study groups: the control group (CG) with a rest interval of 15 s between each, carried out by the and the intervention group [exercise group (EG)]. same investigator in order to avoid any possible bias in The CG received the standard advice relating to AVF from measurement. the nephrology nursing staff. This advice consisted of carrying 690 | I. Tapia González et al. FIGURE 1: Isometric exercises of the distal region: (a) pressure with rubber ball, (b) interpalmar pressure, (c) pressure digital clamp, (d) adduction–abduction, (e) prone cuff supination, (f) pressure cuff, (g) flexoextension with a weight of 1 kg, (h) pressure clamp and (i) interdigital pressure. out isometric exercises on an outpatient basis (repeated squeez- Proximal region. During the first period, four types of isometric ing of a rubber ball and/or lifting weights of 1–2 kg) on the arm exercise were carried out, which consisted of a proximal finger- that had been subjected to the intervention, after a brief verbal tip squeeze, applying distal finger pressure, pronosupination of explanation. the fist with 1 kg and lifting a 1-kg weight. The exercises sched- The EG carried out a protocol-based programme of physical uled for the second period consisted of repeating the exercises isometric exercises in the post-operative period agreed upon from the first period and complementing them with the follow- with the Department of Rehabilitation: the exercises built up as ing exercises: applying finger pressure against a wall and they progressed and were specific for each region and each stretching a band. The same number of series and repetitions study period. were carried out as for the distal region (Figure 2). Similarly, the patients were provided with a monitoring The level of compliance and adherence to the exercise sheet for the isometric physical exercises in which the type of schedule was only analysed for the EG. Patients were assessed exercise was set out along with a corresponding image. A table for compliance (yes or no) if they submitted the outpatient was provided for logging exercises, which was to be filled out monitoring form during follow-up visits. when each exercise was completed, as well as a brief explana- The level of adherence was quantified on the basis of the tion for each exercise. boxes filled out on the monitoring sheet, at both 4 and 8 weeks post-intervention. The following ranges were defined: low (1–7 Distal region. During the first study period, five isometric exer- boxes), low–moderate (8–14 boxes), moderate (15–21 boxes) and cises were carried out in the AVF arm for a period of 4 weeks. high (22–28 boxes). The exercises, which were to be carried out daily, consisted of squeezing a rubber ball, exerting pressure on the palms of the Statistical analysis. Statistical analysis was carried out using the hand, squeezing with the fingertips, adduction–abduction and SPSS Statistics software, version 24.0 (IBM, Armonk, NY, USA). pronosupination of the fist. Quantitative variables were expressed as mean values and stan- In the second study period, the exercises scheduled in the dard deviation (SD). Qualitative variables were expressed as per- first period were repeated with the addition of the following: centages. At the end of the study, quantitative data of the same pressure made with the fist, flexoextension with a weight of group were compared using the paired sample Student’s t-test, 1 kg, squeezing fingertips together and squeezing fingers to- with P  0.05 considered statistically significant. gether across their lengths. A table of equivalences was given to patients to make the exercises more suitable to the patients’ home environment (e.g. 1 kg of rice or lentils). Sets and repeti- RESULTS tions of each scheduled exercise were increased progressively During the study period, 81 VA procedures were carried out every week (Figure 1). at our institution. Fourteen cases of vascular prostheses were Isometric exercises and maturation process | 691 FIGURE 2: Isometric exercises of the proximal region: (a) proximal digital pressure, (b) digital distal pressure, (c) prone supination with 1 kg, (d) weight lifting with 1 kg, (e) digital pressure on wall and (f) stretch with elastic band. Table 1. Sociodemographic parameters Parameters Global EG (n = 30) CG (n = 30) P-value Age (years) 68.6 6 13.0 67.3 6 14.2 69.9 6 11.9 0.199 Sex (men), % (n) 71.3 (42) 66.7 (19) 73.3 (22) 0.500 Charlson Comorbidity Index 6.9 6 2.4 6.9 6 2.8 7.3 6 3.1 0.124 Hypertension, % (n) 91.7 (55) 86.7 (26) 96.7 (29) 0.177 Diabetes mellitus, % (n) 46.7 (28) 46.7 (14) 46.7 (14) 0.602 Dyslipidaemia, % (n) 65 (39) 66.7 (20) 63.3 (19) 0.500 Smokers, % (n) 31.7 (19) 42.1 (8) 57.9 (11) 0.290 Ischaemic heart disease, % (n) 26.7 (16) 16.7 (5) 36.7 (11) 0.072 Handgrip (kg) 22.2 20.7 23.7 0.427 Localization of arteriovenous fistula Distal, % (n) 60 (36) 53.3 (16) 66.7 (20) 0.443 Left, % (n) 80 (48) 80 (24) 80 (24) 0.443 Preoperative variables Lower arm CV diameter (mm) 2.6 6 0.7 2.7 6 0.5 2.5 6 0.7 0.218 Upper arm CV diameter (mm) 3.3 6 0.9 3.5 6 0.6 3.2 6 1.2 0.119 Upper arm BV diameter (mm) 3.9 6 1.2 4.1 6 1.1 3.8 6 1.3 0.259 Bracial artery flow (mL/min) 137.7 6 35.9 142.8 6 35.2 134.6 6 36.6 0.870 Results are expressed by mean 6 SD unless stated otherwise. P <0.05 indicates statistical significance. excluded. Four patients did not submit the informed consent the study (Table 3). No significant differences were found for form. Three patients dropped out during follow-up (one from the groups with respect to Doppler ultrasound variables at the the CG and two from the EG). Finally, 60 patients were analysed: end of the study. In relation to muscle strength, an increase was 30 from the CG and 30 from the EG. observed only in the EG at the end of the study (20.7 6 8.1 versus The main sociodemographic factors are shown in Table 1. 25.1 6 10.3 kg, P ¼ 0.001). The VA most frequently applied was the radiocephalic fistula Table 4 shows the results relating to clinical and ultrasound (60%) with localization on the left side (80%). No significant dif- maturation for both study periods. Clinical maturation was sig- ferences were found between the two study groups. nificantly greater in the EG, both at 4 weeks (CG 33.3% versus EG Table 2 shows the biochemical data and nutritional and hae- 70%, P ¼ 0.009) and at 8 weeks (CG 33.3% versus EG 76.7%, matological parameters, with no differences observed in the P ¼ 0.002) post-intervention. Similarly, the ultrasound matura- data across the two groups. tion was significantly greater in the EG both at 4 weeks (CG 40% The post-operative ultrasound measurements showed sig- versus EG 80%, P ¼ 0.003) and at 8 weeks (CG 43.3% versus EG nificant increases in the diameter of the outflow vein (EG 83.3%, P ¼ 0.003) post-intervention. These significant results 3.3 6 0.8 versus 6.5 6 1.9 mm, P ¼ 0.013; CG 2.9 6 0.6 versus from the EG continued to show significance subsequent to 6.1 6 1.4 mm, P ¼ 0.004) and in the HA flow (EG 142.8 6 35.2 ver- analysis for the different regions (distal and proximal) for all of sus 1647.3 6 999.9 mL/min, P ¼ 0.001; CG 134.6 6 36.6 versus the periods studied. Globally, inadequate vein diameters in 1270.1 6 653.7 mL/min, P ¼ 0.001) in both groups at the end of 95.5%, flow volumes in 31.8% and depths in 28% of cases were 692 | I. Tapia González et al. Table 2. Biochemical parameters EG (n = 30) CG (n = 30) Parameters Baseline End of study P-value Baseline End of study P-value Main biochemical data Glucose (mg/dL) 157.2 6 51.2 153.8 6 72.4 0.845 152.26 32.1 154 6 33.1 0.821 Creatinine (mg/dL) 8.1 6 2.3 8.2 6 3.1 0.924 7.8 6 2.3 7.8 6 2.6 0.985 K (mEq/L) 5.3 6 0.7 5.6 6 0.8 0.726 5.3 6 0.9 5.2 6 1.1 0.964 Ca (mg/dL) 8.8 6 0.8 8.9 6 0.2 0.931 8.8 6 0.4 8.9 6 0.8 0.863 P (mg/dL) 4.4 6 1.2 4.3 6 1.2 0.866 4.5 6 1.4 4.5 6 1.3 0.978 i-PTH (pg/mL) 189.2 6 156.2 170.1 6 132.6 0.872 178.8 6 114 181.7 6 137.9 0.972 Nutritional parameters Albumin (g/dL) 3.8 6 0.3 3.9 6 0.3 0.722 3.8 6 0.3 3.9 6 0.4 0.813 Pre-albumin (mg/dL) 35.3 6 11.2 35.4 6 8.8 0.789 33.6 6 11.1 33.1 6 9.5 0.850 Total cholesterol (mg/dL) 140.1 6 54.2 147.16 57.1 0.346 151.2 6 32.4 148.9 6 34.5 0.721 HDL cholesterol (mg/dL) 42.6 6 11.2 40.2 6 11.9 0.597 42.5 6 10.3 41.6 6 41.6 0.623 Triglycerides (mg/dL) 153.9 6 83.5 156.6 6 75.6 0.724 159.3 6 69.6 154.2 6 73.4 0.497 LDL cholesterol (mg/dL) 66.7 6 44.1 73.4 6 46.8 0.432 69.2 6 65.6 65.7 6 30.5 0.526 Haemogram data Haemoglobin (g/dL) 11.6 6 1.5 11.7 6 1.3 0.793 11.8 6 1.4 11.6 6 1.1 0.726 Ferritin (ng/mL) 434.5 6 271.1 412 6 269.4 0.820 396.8 6 157.1 425.2 6 213.4 0.769 Results are expressed by mean 6 SD. P < 0.05 indicates statistical significance. K, potassium; Ca, calcium; P, phosphorus; i-PTH, intact parathyroid hormone; HDL, high-density lipoprotein; LDL, low density lipoprotein. Table 3. Muscle strength and ultrasound data EG (n = 30) CG (n = 30) Variables Baseline End of study P-value Baseline End of study P-value Muscle strength data (kg) Handgrip 20.7 6 8.1 25.1 6 10.3 0.001* 23.7 6 9.2 23.9 6 9.3 0.703 Ultrasound data Outflow vein diameter (mm) 3.3 6 0.8 6.5 6 1.9 0.013* 2.9 6 0.6 6.1 6 1.4 0.004* Braquial blood flow rate (mL/min) 142.8 6 35.2 1647.3 6 999.9 0.001* 134.6 6 36.6 1270.1 6 653.7 0.001* Results are expressed by mean 6 SD. Statistical significance is indicated by *P < 0.05. Table 4. Clinical and ultrasound maturation rates 4 weeks 8 weeks Variables EG (n = 30) CG (n = 30) P-value EG (n = 30) CG (n = 30) P-value Clinical maturation, % (n) 70 (21) 33.3 (10) 0.009* 76.7 (23) 33.3 (10) 0.002* Ultrasound maturation, % (n) 80 (24) 40 (12) 0.003* 83.3 (25) 43.3 (13) 0.003* Distal territory, % (n) Clinical maturation 60 (12) 40 (8) 0.038* 58.3 (14) 41.7 (10) 0.020* Ultrasound maturation 64.7 (11) 35.3 (6) 0.023* 63.2 (12) 36.8 (7) 0.019* Proximal territory, % (n) Clinical maturation 64.3 (9) 20 (2) 0.040* 71.4 (10) 20 (2) 0.018* Ultrasound maturation 85.7 (12) 40 (4) 0.028* 92.9 (13) 60 (6) 0.049* Statistical significance is indicated by *P < 0.05. the main reasons why AVFs did not mature by the end of the With reference to AVF complications, we only observed study. an increased percentage of significant stenosis in the CG com- The levels of compliance of patients from the EG at 4 and 8 pared with the EG (24 versus 3%, P ¼ 0.026) at the end of weeks were 70 and 66.7%, respectively. Adherence at 4 weeks the study. There were no significant differences for the rest was high in 90% of patients and low in 10%. Adherence at of the AVF complications over the course of the study (no 8 weeks was high in only 65% of cases, moderate in 10%, low– aneurysm, one case of pseudoaneurysm in the EG, 27% moderate in 5% and low in 20%. with haematomas in the CG and 20% in the EG and 6% of Isometric exercises and maturation process | 693 patients with distal hypoperfusion syndrome in the CG and differences were evident, both in terms of the shorter study 3% in the EG). duration (only 2 weeks) as well as the type of exercise performed (exclusively during the HD sessions). We are of the opinion that these two differences alone may explain the greater rate of mat- DISCUSSION uration obtained in our study. The results obtained in our study demonstrate that the imple- Compared with the study by Fontseré et al. [17], with similar mentation of a protocol of post-operative isometric physical patient numbers, clinical and sociodemographic characteristics exercise achieved an improvement in the maturation of autolo- (both in the same geographic area) and methodology applied, gous AVFs for haemodialysis. the results are similar in terms of the rate of autologous AVF An explanation for these findings seems to be that subse- maturation in the EG. Unlike the study by Fontseré et al. [17], in quent to carrying out the AVF procedure, there is evidence of a our study both clinical and ultrasound maturation were also significant increase in laminar blood flow that favours an in- found to be significant at 4 weeks in the AVF created in the crease in nitric oxide (NO) and prostacyclins, leading to vasodi- proximal region. It seems likely that the detailed isometric exer- lation, inhibition of the proliferation and migration of smooth cise programme used in our study (agreed upon with rehabilita- muscle cells and platelet aggregation [16, 25, 26]. Release of per- tions, with a greater number of repetitions and specific to each oxynitrite (an important matrix metalloproteinase activator) in region and time period) could justify this difference. In addition, combination with the NO allows for a long-term structural our study provides significant data on both clinical and ultra- adaptation to the modified blood flow and seems to play an sound maturation at 8 weeks: the usual point in time when important role in vascular remodelling [27, 28]. Exercise pro- punctures are carried out on mature AVFs in clinical practice. motes vascular remodelling, as evidenced by an increase in cap- Tracking data and data on completion of these types of physical illarity within the active muscle and enlargement of the vessels, exercise programmes were also collected, which have not previ- which increases the flow capacity to the muscle [26]. ously been reported in the literature. In this regard, it should be The vital importance of the process of AVF maturation is pointed out that the exercise programme was completed cor- widely known. Adequate AVF maturation leads to its proper rectly by a large number of patients and that adherence within functioning, with fewer complications arising and increased the group of those completing the programme was high in most AVF survival [29]. In spite of current clinical guidelines for cases, therefore we found this to be safe since we did not VA for dialysis, isometric exercises were recommended as a observe any subjects dropping out during the study. We also see strategy to promote maturation of the AVF: the evidence avail- the programme to be effective, given the increase in muscle able to date on the role of physical exercise in the post- strength and how easy the exercises were to perform on an operative period for the improvement of maturation of autolo- outpatient basis. One requirement was that of close monitoring gous AVFs remains very limited. in order to avoid patients dropping out. To date, a few observational studies with several limitations Interestingly, we observed rates of both clinical and ultra- have demonstrated the effects of carrying out different sched- sound maturation that were too low during our measurement ules of post-operative physical exercises, namely isometric controls in the study periods as compared with the literature af- exercises over short periods of time, on autologous AVFs. These ter the creation of autologous AVFs [11, 33]. The greater average exercises have brought about a number of morphological and patient age, the lack of significant comorbidities such a ischae- haemodynamic changes, assessed by means of ultrasound of mic heart disease and smoking, the more distal location of AVFs the AVF (increased thickness and diameter of the outflow vein performed at our centre in order to preserve vascular structures and an increase in brachial artery flow), although their and the increased rate of stenosis observed in the CG all serve direct impacts on AVF maturation have not been evaluated [16, as predictors of poor AVF maturation and could be some of the 18, 30–32]. factors that may be involved in these findings. Other possible After an exhaustive review of the literature, we found only factors include the limited information and advice regarding two randomized controlled studies that have directly evaluated isometric exercises received by patients in the CG, limited to the effects of post-operative physical exercise on the matura- just a brief verbal explanation, and the presumed reduced com- tion of AVFs [17, 19]. In a group of 50 patients, Salimi et al. [19] pliance and adherence in a group without a detailed schedule observed increased clinical (13 versus 5%) but not ultrasound and no subsequent follow-up (the degree of non-compliance in (22 versus 17%) maturation of autologous AVFs 2 weeks after the EG was >30% at the end of the study). It may be that deleting creation when carrying out isometric exercises exclusively dur- these fistulas from the subsequent analysis, at the expense of ing haemodialysis sessions. Similarly, Fontseré et al. [17] ana- being able to develop late maturation or perform an early inter- lysed clinical and ultrasound maturation of AVFs in 72 patients vention in cases of surgical complications (not included in the after carrying out a post-operative programme of isometric design of the study), could improve the survival rates in this exercises, as compared with 1 month prior to the programme’s group. In the same way, carrying out outpatient follow-up in creation, carried out on an outpatient basis. In this way, the the CG could also reveal some differences, although it would be authors were able to conclude that these isometric exercises difficult to carry out reliable patient monitoring in such a group had increased clinical maturation of AVFs at 1 month from crea- after they had received a brief verbal explanation without a tion and therefore this type of exercise programme should be schedule for controlled exercises. considered for the maturation process, especially in the distal Regarding AVF complications, we did not find any episodes region. of thrombosis in our study. It is probable that our exhaustive In a general sense, our results are virtually identical to those preoperative physical and ultrasound examinations selected obtained in previously published studies, both in terms of the the optimal VA sites. Furthermore, the follow-up period could morphological and haemodynamic changes, as well as in terms be shortened to detect any episode of thrombosis. of the benefits of maturation of the AVF. However, there are The main points of interest in our study are based on its ran- some differences that should be highlighted. In relation to the domized design, carried out without any source of funding, study by Salimi et al. [19], we found large methodological as well as the comprehensive methodology applied, with the 694 | I. Tapia González et al. creation of a schedule of approved isometric exercises that are Dialysis Outcomes and Practice Patterns Study. Nephrol Dial safe and adapted to the location and maturation stage of the Transplant 2008; 23: 3219–3226 AVF created. The exercises are easy for patients to perform on 10. Kumbar L, Karim J, Besarab A. Surveillance and monitoring an outpatient basis and offer the possibility of logging and mon- of dialysis access. Int J Nephrol 2012; 2012: 649735 itoring of compliance in daily clinical practice. 11. Rooijens PP, Tordoir JH, Stijnen T et al. Radiocephalic wrist With reference to the limitations of our study, the small arteriovenous fistula for hemodialysis: meta-analysis indi- sample size should be highlighted, both due to the small num- cates a high primary failure rate. Eur J Vasc Endovasc Surg ber of VA procedures carried out each year at our institution 2004; 28: 583–589 and the specific methodology used. The latter has made it diffi- 12. Dhingra RK, Young EW, Hulbert-Shearon TE et al. Type of cult for other nearby hospitals to participate, which would have vascular access and mortality in U.S. hemodialysis patients. allowed a greater number of patients to be included. Kidney Int 2001; 60: 1443–1451 13. Burkhart HM, Cikrit DF. Arteriovenous fistulae for hemodial- ysis. Semin Vasc Surg 1997; 10: 162–165 CONCLUSION 14. Yap H-Y, Pang S-C, Tan C-S et al. Catheter-related complica- In conclusion, our study suggests that a post-operative pro- tions and survival among incident hemodialysis patients in gramme of isometric exercises for AVF offers, at both 4 and Singapore. J Vasc Access 2018; 19: 602–608 15. Hemodialysis Adequacy 2006 Work Group. Clinical practice 8 weeks, greater clinical and ultrasound maturation in the distal guidelines for hemodialysis adequacy, update 2006. Am J and proximal regions of the arms. Pending further studies in Kidney Dis 2006; 48(Suppl 1): S2–S90 the future, we intend to maintain the current recommendations 16. Oder TF, Teodorescu V, Uribarri J. Effect of exercise on the di- based on carrying out physical exercise during the maturation ameter of arteriovenous fistulae in hemodialysis patients. process with our patients. ASAIO J 2003; 49: 554–555 17. Fontseré N, Mestres G, Yugueros X et al. Effect of a postopera- ACKNOWLEDGEMENTS tive exercise program on arteriovenous fistula maturation: a Thanks to Dr Lucı́a Martı́nez Carnovale for her valuable randomized controlled trial. Hemodial Int 2016; 20: 306–314 cooperation in this study. This study has been carried out 18. Leaf DA, MacRae H-H, Grant E et al. Isometric exercise increases the size of forearm veins in patients with chronic within the framework of the PhD programme in medicine at renal failure. Am J Med Sci 2003; 325: 115–119 the Universitat Autónoma de Barcelona. 19. Salimi F, Nassiri GM, Moradi M et al. Assessment of effects of upper extremity exercise with arm tourniquet on maturity CONFLICT OF INTEREST STATEMENT of arteriovenous fistula in hemodialysis patients. J Vasc Access 2013; 14: 239–244 None declared. 20. Haidar SG, Kumar D, Bassi RS et al. Average versus maximum grip strength: which is more consistent? J Hand Surg Br 2004; REFERENCES 29: 82–84 21. O’Driscoll SW, Horii E, Ness R et al. The relationship between 1. Santoro D, Benedetto F, Mondello P et al. Vascular access for wrist position, grasp size, and grip strength. J Hand Surg Am hemodialysis: current perspectives. Int J Nephrol Renovasc Dis 1992; 17: 169–177 2014; 7: 281–294 22. Mathiowetz V, Kashman N, Volland G et al. Grip and pinch 2. Gibson KD, Gillen DL, Caps MT et al. Vascular access survival strength: normative data for adults. Arch Phys Med Rehabil and incidence of revisions: a comparison of prosthetic 1985; 66: 69–74 grafts, simple autogenous fistulas, and venous transposition 23. Wiese P, Nonnast-Daniel B. Colour Doppler ultrasound in di- fistulas from the United States Renal Data System Dialysis alysis access. Nephrol Dial Transplant 2004; 19: 1956–1963 Morbidity and Mortality Study. J Vasc Surg 2001; 34: 694–700 24. Lomonte C, Casucci F, Antonelli M et al. Is there a place for 3. Allon M, Robbin ML. Increasing arteriovenous fistulas in he- duplex screening of the brachial artery in the maturation of modialysis patients: problems and solutions. Kidney Int 2002; arteriovenous fistulas? Semin Dial 2005; 18: 243–246 62: 1109–1124 25. Pol MM. Hand exercise for arteriovenous fistula. Glob Surg 4. Rodrı́guez Hernández JA, González Parra E, Julián Gutiérrez 2018; 4: 1–3 JM et al. Vascular access guidelines for hemodialysis. 26. Prior BM, Lloyd PG, Yang HT et al. Exercise-induced vascular Nefrologia 2005; 25(Suppl 1): 3–97 remodeling. Exerc Sport Sci Rev 2003; 31: 26–33 5. Ibeas J, Roca-Tey R, Vallespı́n J et al. Spanish clinical guide- 27. Lehoux S, Castier Y, Tedgui A. Molecular mechanisms of the lines on vascular access for haemodialysis. Nefrologia 2017; vascular responses to haemodynamic forces. J Intern Med 37(Suppl 1): 1–193 2006; 259: 381–392 6. Kukita K, Ohira S, Amano I et al. 2011 update Japanese 28. Castier Y, Brandes RP, Leseche G et al. p47phox-dependent Society for Dialysis Therapy Guidelines of Vascular Access NADPH oxidase regulates flow-induced vascular remodel- Construction and Repair for Chronic Hemodialysis. Ther ing. Circ Res 2005; 97: 533–540 Apher Dial 2015; 19(Suppl 1): 1–39 29. Malovrh M. Non-matured arteriovenous fistulae for haemo- 7. Vascular Access Work Group. Clinical practice guidelines for dialysis: diagnosis, endovascular and surgical treatment. vascular access. Am J Kidney Dis 2006; 48(Suppl 1): S248–S273 Bosn J Basic Med Sci 2010; 10(Suppl 1): S13–S17 8. Ng LJ, Chen F, Pisoni RL et al. Hospitalization risks related to 30. Turmel-Rodrigues LA, Bourquelot P, Pengloan J. Hemodialy- vascular access type among incident US hemodialysis sis arteriovenous fistula maturity: US evaluation. Radiology patients. Nephrol Dial Transplant 2011; 26: 3659–3666 2003; 227: 906–907 9. Ethier J, Mendelssohn DC, Elder SJ et al. Vascular access 31. Khavanin Zadeh M, Gholipour F, Naderpour Z et al. use and outcomes: an international perspective from the Relationship between vessel diameter and time to Isometric exercises and maturation process | 695 maturation of arteriovenous fistula for hemodialysis access. 33. Rooijens PP, Burgmans JP, Yo TI et al. Autogenous radial- Int J Nephrol 2012; 2012: 942950 cephalic or prosthetic brachial-antecubital forearm loop 32. Kong S, Lee KS, Kim J et al. The effect of two different hand AVF in patients with compromised vessels. A randomized, exercises on grip strength, forearm circumference, and vas- multicenter study of the patency of primary hemodialysis cular maturation in patients who underwent arteriovenous access. J Vasc Surg 2005; 42: 481–487 fistula surgery. Ann Rehabil Med 2014; 38: 648