Effects of Individualized Forearm Isometric Exercise on Blood Flow Volume After Arteriovenous Fistula Surgery: A Case Series

Introduction

End-stage renal disease (ESRD) is a global health problem with an increased incidence of 18.4% from 2005 to 2015 [1]. The number of patients with ESRD is expected to reach 2 million by 2030 [2]. Hemodialysis is one of the main therapies in ESRD. An arteriovenous fistulas (AVF) is the main choice of hemodialysis access because it has fewer complications, a lower mortality risk, and a longer patency rate than other methods of venous access [3].

Maturation failure is one of the most common problems with AVF, occurring in 20% to 50% of cases [4]. Failure of vascular access can affect the dose of hemodialysis administered, which increases the risk of morbidity and mortality [5]. A well-functioning AVF is therefore essential for hemodialysis efficiency.

Before it can be used as a hemodialysis access, an AVF takes an average of 6 to 12 weeks to reach maturation [6]. AVF maturation is evaluated clinically as well as radiologically by assessing vessel diameter, vein depth, and blood flow volume in the vein. Blood flow volume is one of the important parameters of AVF maturation assessment [7]. Recent evidence highlights the importance of structured exercise, especially isometric regimens, in promoting vascular adaptation after AVF creation [4–6].

Physical exercise and muscle contraction are potent stimuli to changes in vascular structure. Increased blood flow through the blood vessels will increase shear stress, which is a major stimulus in the enlargement of blood vessel diameter [8]. Hand exercises have been shown to be effective in improving vasodilation and fistula maturation, thereby reducing mortality after AVF procedures [9]. Unlike general hand exercises, isometric regimens provide controlled muscle contractions that generate stable shear stress and have been associated with improved blood flow and vein diameter in randomized controlled trials and systematic reviews [5,6,10]. These studies demonstrate that isometric handgrip programs enhance blood flow volume and vein diameter in patients with AVFs [5,6,10].

In this case series, we examine the effect of a 4-week forearm isometric exercise regimen on blood flow volume in patients who recently underwent radiocephalic AVF formation. This study is aimed to provide insights into the potential benefits of such a regimen in promoting AVF maturation and function.

Case Reports

Three patients participated in this case series, each having undergone radiocephalic AVF formation. This intervention was performed at Hasanuddin University Hospital in Makassar, Indonesia. Written informed consent was obtained from all patients. Baseline blood flow volume was measured using Doppler ultrasound before the commencement of the exercise program. Patient A presented with an initial blood flow volume of 175 mL/min, patient B with 299 mL/min, and patient C with 289 mL/min. These measurements provided the foundational data to assess the effect of the exercise regimen on AVF blood flow. The intervention consisted of a structured forearm isometric exercise regimen performed over 4 weeks (Figure 1). Each patient performed the exercises with the following prescription: frequency: twice daily; intensity: 50% of maximum voluntary isometric contraction; duration: 10-second hold per repetition; number of repetitions: 10 repetitions per set; and number of sets: 3 sets per session. This regimen was designed to progressively enhance vascular response without causing undue strain. Upon completion of the 4-week exercise program, blood flow volume was reassessed using Doppler ultrasound (Figure 2). The results demonstrated a substantial increase in blood flow volume for all 3 patients, from 175 to 559 mL/min in patient A, from 299 to 633 mL/min in patient B, and from 289 to 725 mL/min in patient C.

Discussion

This case series showed that dose-specific exercise increased blood flow volume in 3 patients. These results support previous studies showing that hand exercises can significantly increase venous diameter and blood flow volume after an exercise program. Previous studies by Poetra et al [10] and Kong et al [6] demonstrated a significant increase in cephalic vein diameter and blood flow volume with handgrip resistance exercises at a 10-repetition maximum, performed twice in the morning and twice in the afternoon. Each session included 3 sets of 10 handgrips, with a 1-minute break between each set, performed for 4 weeks and 5 weeks, respectively [6,10]. In other study without an individualized exercise prescription, the mean blood flow volume after 5 weeks of exercise was 575 mL/min [11]. In the present case series, the blood flow volume after 4 weeks of individualized exercise reached a mean of 639 mL/min.

Studies on the vascular response to exercise in both healthy and diseased populations have generated novel hypotheses regarding the cellular, metabolic, and mechanical mechanisms underlying the effects of physical activity [8]. It was once thought that muscle contraction was directly linked to the acute vascular response to physical exertion, with contractile activity increasing blood flow to skeletal muscle. The primary factor driving the enlargement of vessel diameter is shear stress, which rises as blood flow increases. This increase in shear stress triggers the flow-mediated vasodilation mechanism [12].

The pressure gradient between the 2 ends of the channel and the resistance to blood flow are the 2 main factors that determine blood flow through the vascular circuit [12]. The vessel’s radius is the most significant element in determining this resistance [12,13]. The relationship between vascular resistance and vessel radius is inverse. Vascular resistance can rise or fall in response to modifications in vessel diameter. Resistance increases with decreasing vascular size, and vice versa. The vessel’s cross-sectional area is equal to the square of the radius [13]. The low-pressure venous system and the high-pressure artery system are connected via the fistula, which also works as a short circuit. Reducing peripheral resistance and significantly increasing flow are achieved by opening the fistula. The fistulous circuit must broaden in order to allow for the increased amount of blood flow via the fistula without unnecessarily raising the wall shear stress. Both vascular remodeling and vasodilatation lead to an increase in flow [13].

Conclusions

This case series shows that individualized forearm isometric exercise can effectively increase blood flow volume in patients following AVF creation. These positive results require further investigation with larger-scale studies to determine the appropriate exercise regimen.