|Year : 2019 | Volume
| Issue : 4 | Page : 257-260
Hemodialysis arteriovenous fistula maturation and role of perioperative vascular mapping
Ramesh Dasari1, Siva Parvathi Karanam2, Anil Kumar1, A Tyagi1, Siva Kumar2, AY Lakshmi3
1 Department of Urology, Sri Venkateswara Institute of Medical Sciences, Tirupati, Andhra Pradesh, India
2 Department of Nephrology, Sri Venkateswara Institute of Medical Sciences, Tirupati, Andhra Pradesh, India
3 Department of Radiology, Sri Venkateswara Institute of Medical Sciences, Tirupati, Andhra Pradesh, India
|Date of Submission||24-Sep-2019|
|Date of Acceptance||17-Oct-2019|
|Date of Web Publication||16-Dec-2019|
Dr. Siva Parvathi Karanam
Department of Nephrology, Sri Venkateswara Institute of Medical Sciences, Tirupati, Andhra Pradesh
Source of Support: None, Conflict of Interest: None
Introduction: The arteriovenous fistula (AVF) is the preferred access in patients starting on maintenance hemodialysis. The vasculature of the upper limb has a dominant role in determining the successful outcome of AVF surgery. Hence, we aimed to determine the various vascular parameters both preoperatively and postoperatively at prespecified intervals and their impact on AVF outcomes.
Materials and Methods: It was a prospective observational study done during 18 months period. Ultrasound with doppler color flow evaluation was done to look for radial artery diameter, cephalic vein diameter, radial artery flow, and peak systolic velocity both preoperatively and postoperatively at postoperative day 1 (POD) 1, 8 weeks, and 3 months.
Results: A total of 120 patients were evaluated with a mean age of 50.2 ± 12.01. The male: female ratio was 2.75:1. The etiology of the end-stage renal disease was diabetes-related in 41.6% and the remaining 58.4% were of nondiabetic. The overall success rate was 68.3%, with 31.7% failure rate. On comparison between the successful and failed AV fistula groups, a statistically significant difference was found in relation to the pre and post procedural vascular diameter and flow rates between the groups. The mean cephalic vein diameter in those with successful AVF was 2.17 mm and 1.90 mm in those with a failed AVF.
Conclusion: In our study, the Cephalic vein size, radial arterial diameter, peak systolic velocity, radial artery flow rate preoperatively, and increase in flow rate at POD1 and POD 8 along with the increase in cephalic vein diameter were the predominant factors determining the success of the radiocephalic fistula. This is strong evidence that routine preoperative duplex ultrasonography reduces the rate of primary fistula failure and unnecessary surgical exploration when used for selection of vessels for AVF preoperatively as well as postoperative monitoring of AVF during the period of follow-up. A minimum arterial diameter of 2 mm is associated with successful fistula formation. Below this diameter, the ability of an artery to increase flow and dilate will determine fistula success.
Keywords: AVF maturation, role of doppler ultrasound, primary AVF failure
|How to cite this article:|
Dasari R, Karanam SP, Kumar A, Tyagi A, Kumar S, Lakshmi A Y. Hemodialysis arteriovenous fistula maturation and role of perioperative vascular mapping. J NTR Univ Health Sci 2019;8:257-60
|How to cite this URL:|
Dasari R, Karanam SP, Kumar A, Tyagi A, Kumar S, Lakshmi A Y. Hemodialysis arteriovenous fistula maturation and role of perioperative vascular mapping. J NTR Univ Health Sci [serial online] 2019 [cited 2020 Apr 4];8:257-60. Available from: http://www.jdrntruhs.org/text.asp?2019/8/4/257/273132
| Introduction|| |
The arteriovenous fistula (AVF) is the vascular access of choice in maintenance hemodialysis patients. However, a significant percentage (up to 30%) of fistulae fail early—within 3 months of surgery. Some fistulae thrombose in the first 24 h of the operation, usually as a result of technical errors, and others do not mature or functionally usable as the blood flow through them is not sufficiently high for hemodialysis. The cause of most early failures is often unclear although the quality of the vessels is thought to play an important role. Small-sized, stenosed, or partially thrombosed cephalic veins and atherosclerotic or small-sized radial arteries have been suggested as possible causes. Keeping these in view, it may be prudent to perform preprocedural mapping and a follow-up in the postprocedural period with the help of a noninvasive, easily available, repeatable, reproducible, cost containing method such as ultrasound doppler with color flow evaluation, which is useful in assessing the outcomes of AV fistula creation. Here, we bring forth our approach and outcomes of upper limb radiocephalic arterio-venous fistula, undertaken during the study period.
| Materials and Methods|| |
This was a prospective observational study of one and half years, included all patients of chronic renal failure requiring AV fistula surgery. The patients whose vascular anatomy did not permit the construction of a native AV fistula (on preoperative Doppler ultrasound) were excluded. The criteria used for an exclusion based on clinical examination including modified Allen's test and on ultrasound study were radial artery diameter at wrist level less than 1.6 mm and the presence of stenosis in the main cephalic vein. Patients underwent careful history taking and clinical examination for the diagnosis of the disease and requirement of native AV fistula creation. The study participants were informed about protocol and requirement of regular follow-up for the completion of study and informed consent was obtained. The study was conducted after obtaining institutional research and ethics committee approvals. Ethics approval has been obtained, date of approval is 11-06-2015.
The patients' vessel status of upper limb arterial and venous systems was recorded preoperatively by a Doppler ultrasound. The cephalic vein and radial artery would be imaged from wrist to proximal upper arm to note any stenosis/thrombus in the vessel. Radial artery flow was recorded at wrist level. Postoperative follow-up was done on day 1, at 8 weeks, and at 3 months (3 months are the maximum time interval required for AVF maturation), using color Doppler ultrasound scanner (Esaote MyLab40 with 10 MHz linear-array transducer) by a dedicated qualified radiologist. Arteries were evaluated in terms of course, caliber, depth from skin, direction of flow, patency, and Doppler spectral wave patterns at arm, upper forearm, and distal forearm levels. Similarly, veins were also evaluated at specific checkpoints. For ease of conceptualization, the examination follows the flow of blood, beginning with the feeding artery and moving through the anastomosis and draining vein. The examination always included the draining subclavian vein, because there is a high prevalence of stenosis or occlusion of this vein secondary to previous catheterization for temporary hemodialysis. The native artery distal to the fistula is evaluated for patency, direction of flow, depth from skin, and flow characters like peak systolic velocity (PSV) and resistive index. The examination was performed in both longitudinal and transverse planes and spectral waveforms were obtained at each examination level with color Doppler, and flow volume across the fistula was calculated.
Statistical analysis was performed using SPSS 16 software. Continuous variables were expressed as mean with standard deviation and categorical values as percentages. Mann–Whitney U test or independent t-test was used for analysis depending upon the distribution of variables, and Chi-square test was used for comparing categorical variables; P value < 0.05 was considered statistically significant.
| Results|| |
A prospective study was conducted on 120 patients of chronic kidney disease stage 4 and 5 during a period of 18 months. The mean age of the patients was 50.2 ± 12.01. The male: female ratio was 2.75:1. The etiology of the end-stage renal disease was diabetes-related in 41.6% and the remaining 58.4% were of nondiabetic. The comorbidities were hypertension in 65%, diabetes in 41.6%, and ischemic heart disease in 8.3%. The pre and post procedural vascular diameters and flow rates were shown in [Table 1] and [Table 2], respectively. The overall success rate was 68.3%, with 31.7% failure rate. On comparison between the successful and failed AV fistula groups, no statistically significant difference was noted in relation to age, sex, diabetes, hypertension, and ischemic heart disease, whereas a statistically significant difference was found in relation to the pre and post procedural vascular diameter/flow rates between the groups [Table 3].
|Table 3: Parameters and Their Measurements Pre And Post Avf Creation at Prespecified Intervals|
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| Discussion|| |
The radiocephalic AVF is usually the vascular access created in majority of the hemodialysis patients; it is associated with significant primary failure rates for various reasons like accelerated atherosclerosis in uremic patients which may be associated with reduced peak systolic velocity and reduced ability to increase the access flow after creation of vascular access, as well as the inflammatory changes associated with the uremia affect the veins and their ability to dilate after vascular access creation.
Hence, the current study focused on demographic factors, comorbidities, arterial diameter, venous diameter preoperatively, and peak systolic flow velocity, flow rate, and diameter of the vessels at POD 8 weeks and their effect on AVF patency. The mean cephalic vein diameter in those with successful AVF was 2.17 mm and 1.90 mm in those with a failed AVF which was low compared to the study by Brimble et al. which was 2.52 mm and 2.23 mm, respectively. The success rate of AVF was higher in patients with a mean cephalic vein diameter greater than 2 mm. Although a precise threshold for minimal vein diameter in successful fistulae has not been established, most clinical studies use a cut off value of 2.5 mm for AVF and 4.0 mm for synthetic grafts as suggested by Silva et al. The ability of a vein to dilate is also an important predictor of successful fistulae. We found that cephalic venous diameter increased by an average of 49% in patients with successful fistulae similar to the findings of Malovrh in which venous diameter increased by an average of 48% in patients with successful fistulae.
There is limited literature on the influence of arterial diameter and vessel quality on fistula success rate. The early failure rate was 84% if the radial artery diameter was less than 2 mm in our study, which was similar to the study by Lemson et al., while it was high when compared to the study by Wong et al. which was 1.6 mm. Our patients might require higher minimum diameter for a successful fistula. We have observed a success rate of 57% when radial artery diameter was less than 2 mm, while Malovrh reported that a diameter of <1.5 mm was associated a success rate of only 45%. Adequate arterial inflow is crucial for fistula maturation. However, accurate preoperative flow rates are difficult to measure due to the small diameter of the radial artery.
The mean flow rate of radial artery was 58.7 ml/min in those with successful AVF, which was similar to the findings by Malovrh who also reported a mean preoperative flow rate of 54.5 ml/min in AVF with a successful outcome; however, the mean flow rate of radial artery in those with failed fistula was 40.63 ml/min which was high when compared to the study by Malovrh which was 24.1 ml/min. Within 24 h of surgery to create a fistula, the fistula blood flow was up to 188.4 ml/min in patients with successful fistula.
The mean blood flow rate increased to 696 ml/min at 8 weeks in those with successful fistula. PSV of the proposed inflow artery is easier to measure and has also been evaluated as a predictor of a successful AVF. A threshold PSV of at least 50 cm/s is suggested for fistula success. Lockhart found no difference in preoperative PSV between adequate and inadequate fistulae and no increased failure rates with a PSV of <50 cm/s; however, our study found that preoperative PSV was 49.8 cm/s in those with a successful fistula, while it was 40.6 cm/s in those with a failed fistula with statistical significance.
Although there are some studies which found age, sex, presence of diabetes and hypertension with outcomes of AVF, our study did not find any correlation with age, sex, and presence of diabetes and hypertension with outcomes of AVF. Our study found a correlation with preoperative radial artery diameter, cephalic vein diameter, and radial artery flow with AVF outcomes similar to other studies.
| Conclusion|| |
In our study, the cephalic vein size, radial arterial diameter, PSV, radial artery flow rate preoperatively, and increase in flow rate at POD1 and POD 8 along with the increase in cephalic vein diameter were the predominant factors determining the success of the radiocephalic fistula. This is strong evidence that routine preoperative duplex ultrasonography reduces the rate of primary fistula failure and unnecessary surgical exploration when used for selection of vessels for AVF preoperatively as well as postoperative monitoring of AVF during the period of follow-up. A minimum arterial diameter of 2 mm is associated with successful fistula formation. Below this diameter, the ability of an artery to increase flow and dilate will determine fistula success.
| Limitations|| |
This study has assessed only primary failures. Secondary failures are not assessed because it requires long term follow-up as the present study is a short duration follow-up study. Other factors that determine the success of AVF maturation like the surgeon performing the procedure whether trainee or expert consultant were not studied.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form, the patients have given their consent for their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3]