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Saudi Journal of Kidney Diseases and Transplantation
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RENAL DATA FROM THE ASIA - AFRICA Table of Contents   
Year : 2008  |  Volume : 19  |  Issue : 2  |  Page : 280-285
The Patency Rate and Complications of Polytetrafluoroethylene Vascular Access Grafts in Hemodialysis Patients: A Prospective Study from Iran


Surgery Department, Sina Hospital School of Medicine, Medical Sciences/University of Tehran, Tehran, Iran

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   Abstract 

The objective of this study was to evaluate the patency rate as well as complications of polytetrafluoroethylene vascular grafts (ePTFE) in patients on hemodialysis (HD). In a prospective study, 84 patients who underwent implantation of vascular grafts for HD at the Sina Hospital, Tehran, Iran, between April 2001 and April 2004, were evaluated. The mean age of the patients was 55 + 12 years; and 42 patients were male. Upper and lower limb vascular access grafts were implanted in 42 patients each. The patients were followed-up for a mean of 24 months. During this period, 30 patients (35.7%) developed thrombosis and two (2.4%) had bleeding. Graft infection and pseudo-aneurysm were observed in five (6%) and two (2.4%) patients, respectively. The primary 24-month patency rate was 43%. The patency rates in patients with and without hypertension were 29.7% and 62.2%, respectively (P < 0.03). Upper extremity grafts had 60% patency rate while lower extremity grafts had a patency rate of 26% (P < 0.05). Our study indicates that ePTFE vascular graft seems to be an appropriate vascular access when arteriovenous fistulas cannot be constructed . Educating patients and maintaining proper care of the grafts will help in reducing prevalence of infection, thrombosis and other complications, can increase the patency rate of the grafts and consequently, decrease the morbidity rate in HD patients.

Keywords: Hemodialysis, Patency rate, Vascular graft, Thrombosis, Polytetrafluoroethylene graft

How to cite this article:
Salimi J, Zafarghandi MR. The Patency Rate and Complications of Polytetrafluoroethylene Vascular Access Grafts in Hemodialysis Patients: A Prospective Study from Iran . Saudi J Kidney Dis Transpl 2008;19:280-5

How to cite this URL:
Salimi J, Zafarghandi MR. The Patency Rate and Complications of Polytetrafluoroethylene Vascular Access Grafts in Hemodialysis Patients: A Prospective Study from Iran . Saudi J Kidney Dis Transpl [serial online] 2008 [cited 2019 Nov 12];19:280-5. Available from: http://www.sjkdt.org/text.asp?2008/19/2/280/39046

   Introduction Top


Kidney dysfunction and the resulting com­plications have always been a problem in the medical society since many years and remains one of the major causes of mortality worldwide. [1] Hemodialysis (HD) has emerged as a life saving form of treatment in patients with kidney dysfunction. Establishing a sui­table vascular access is necessary for per­forming HD and finding one has remained a major problem. [2] In 1960, Quinton et al, invented external shunts and in 1962, Bresica et al used arteriovenous fistulas (AVFs). [1],[3]

Despite the definite advantages offered by AVFs, some patients cannot continue using them (from the beginning or after some time) due to either atherosclerosis or due to lack of proper vessels. [4] Consequently, researchers sought new methods and suggested using cow carotid arteries, Dacron grafts and human umbilical vessels. [2],[4],[5],[6] Poly­ tetrafluoroethylene (ePTFE) synthetic vas­cular prosthesis was invented in 1976. [3] These prostheses are presently the most commonly used industrialized prostheses for HD patients. Vascular grafts are increasingly used in Iran; thus, determining the patency rate and risk factors for vascular graft failure can assist in selecting patients as well as the graft-care methods. In this prospective study, demographic factors of failure and patency rates, occurrence of complications and the impact of the risk factors on the performance of vascular grafts in upper and lower limbs are evaluated.


   Materials and Methods Top


The present study was conducted from April 2001 to April 2004 at the Sina Hospital, which is affiliated to the Tehran University of Medical Sciences. A member of the vascular surgery team examined all patients referred by the Iranian Dialysis Center, and the status of the peripheral vessels was assessed. In case the vessels were proper, the patient was considered as a candidate for AVF; otherwise, ePTFE vascular graft was used. Also, cases where the AVF created earlier did not work properly and performing another surgery was not possible, were con­sidered for receiving grafts.

Polytetrafluoroethylene vascular grafts manu­factured by the American factory of GORE under the brand of GORE-TEX were utilized in all patients. Institutional review board approval was obtained and all patients signed an informed consent form before undergoing surgery.

Lower limb grafts were implanted in 42 patients (50%) and upper limb grafts were used for another 42 patients (50%). The graft site was decided upon based on previous surgical records of patients as well as the existence of proper arteries and vessels for implanting the graft.

Demographic factors and the following variables were recorded for all patients before hospitalization, using a questionnaire: age, sex, number of weekly dialysis sessions and presence of diabetes and hypertension. Following the surgical operation, the patients whose grafts performed well entered the study and those with dysfunctioning grafts were excluded from the study. The patients were followed-up periodically and the follo­wing complications resulting in graft failure were recorded: thrombosis/infection or both and pseudo-aneurysm.

The follow-up period for each patient was at least 24 months. The duration of study from the beginning to the end of follow-up with the last patient took 35 months Survival distributions were plotted using the Kaplan­Meier method for graft survival (primary patency). Log rank tests were used to evaluate statistical differences in survival distribution between different groups. [7]


   Results Top


In the present study, 84 patients were recruited, the mean age of whom was 55 ± 12 years with a range of 6-77 years. Among the patients, 42 (50%) were female and upper and lower limb grafts were implanted in 42 patients (50%) each. Hypertension (45 cases, 53.6%), diabetes (26 cases, 31%) and smoking (19 cases, 22.6%) were considered as athero­sclerosis risk factors.

The patients were followed-up for at least 24 and up to 36 months. During the follow-up period, 39 cases died (CI 95% = 35.8 - 57.1%, 46.4%) and seven patients (CI 95% = 2.4%-8.3%, 14.2%) underwent kidney transplantation.

Graft Patency Rate

Based on Kaplan-Maier analysis, the graft patency rate in the 6 th , 12 th , 18 th and the 24 th months of follow-up was 78% (CI 95% = 69.8 - 87.3%), 63.3% (CI 95% = 52.8 - 73.4%), 54.9% (CI 95% = 44.1 - 65.4%) and 43% (CI 95%=32.3-53.4%), respectively [Figure - 1].

The complementary Log-Rank test was used to examine the effect of various factors including age, gender, history of hyperten­sion, history of diabetes and, graft site on the patency rate, in addition to the type and prevalence of complications. We found that none of the factors other than hypertension and graft site had a significant relationship with the 24-month patency rate as well as the prevalence of complications. The 24-month patency rate in patients with and without hypertension was 29.7% and 62.2%, respect­tively; the difference was significant (P = 0.03). Also, the patency rate demonstrated a significant difference in the upper limb (60%) in contrast to the lower limbs (26%); this could be one of the reasons why patients with hypertension and those receiving lower limb grafts had a poorer survival rate [Figure - 2],[Figure - 3].

Graft Complications

During the follow-up period, 39 cases (46.4%) (CI 95%=35.8-57.1%) developed complications, which included the following: 30 cases of thrombosis (the most common complication) (35.7%), five cases of infection of the vascular graft (2.4%), two cases each of graft bleeding and pseudo-aneurysm in the graft site (2.4%).


   Discussion Top


The number of patients requiring HD is increasing due to the advances made in diagnosis and treatment. Many patients are exposed to early vascular problems because of age, hyperlipidemia, hypertension and atherosclerosis; thus, the benefit of using AVFs cannot be provided to all patients. Due to their specific attributes such as low thrombogenicity, durability against needling and their availability with different thick­nesses, ePTFE vascular graft can be consi­dered to serve as a connection between the suitable arteries and veins and provide an appropriate vascular access for performing HD. [4] Considering the problems of vascular surgery and the high cost of vascular grafts, preserving the implemented grafts is vital for the patients' well being.

In an earlier study, the 24-month patency rate was 83% and the most common com­plications were thrombosis (27%), graft infection (21%) and pseudo-aneurysm (11%). There was no relationship between diabetes and the graft patency rate in the mentioned study. [4] Compared with the present study, their patency rate was higher and thrombosis was lower.

With respect to the graft site, the results of our study are similar to some of the other studies with upper limb grafts having higher patency rates when compared to lower limb grafts. [7],[8],[9],[10]

In another study on 86 patients, the one­year patency rate was reported to be nearly 43%. [11] In a study carried out on 59 grafts, the one-year patency rate was 50%. The only factor affecting the patency rate was diabetes in this study. [12] However, in the present study, only hypertension affected the patency rate as well as the prevalence of complications.

Based on earlier studies, it seems that the average one-year patency rate is 58%. [5],[11],[13] All the above mentioned studies reported a higher one-year patency rate than our study. The difference in the statistics among the studies may be due to the following reasons:

a). Using grafts, the thickness of which was different on the two sides and could connect the arteries and different vessels.

b). Familiarity of the personnel in HD units with the use of vascular access grafts and hemostats, following the disconnection of the HD machine

c). Lack of taking periodic care of grafts

Contrary to the other studies, there were no re-openings in the present study. The chief reason was the untimely referral of the patients and missing the golden treat­ment time. Considering the fact that the percentage of successful re-openings has been reported to be up to 42.5%, and that it could increase the secondary patency rate to 80%, it is necessary to train the patients for regular referrals. [4],[11],[14],[15]

The most common complication leading to dysfunction of the graft was thrombosis in this study, as in other studies. The existence of tightness, particularly in the vascular anastomosis site, is the major cause of thrombosis, and applying the recommen­dation of the National Kidney Foundation for graft surveillance technique is necessary. The technique includes the calculation of: the amount and percentage of blood flow recirculation, the graft blood flow rate and the venous line pressure.[14]

These factors can contribute to the early diagnosis of grafts at risk by identifying the grafts with low blood flow rate, which is a sign of stenosis, thus carrying out an early surgery, which can increase the graft patency rate.


   Conclusions Top


Based on our experience, the following suggestions can be put forward:

a). The priority of using the upper limb for implanting grafts

b). Providing facilities and devising the required programs for implanting the graft as well as surveillance technique, in order to specify the grafts at risk of dysfunction

c). Omitting and controlling the risk factors like hypertension

d). Training the patients and the personnel in HD units on vascular graft preservation


   Acknowledgment Top


We would like to thank Miss Bita Pourmad for her cooperation in performing in this study.

 
   References Top

1.Feldman H , Heid PJ, Hutchinson JT, Stoiber E, Hartigan MF, Berlin JA. Hemodialysis vascular access morbidity in the United States. Kidney Int 1993;43(5):1091-6.  Back to cited text no. 1    
2.Pisoni RL, Young EW, Dykstra DM, et al. Vascular access use in Europe and the United State: Results from the DOPPS. Kidney Int 2002;61(1):305-16.  Back to cited text no. 2    
3.Konner K. History of vascular access for hemodialysis. Nephrol Dial Transplant 2005;20(12):2629-35.  Back to cited text no. 3    
4.Chia KH, Ong HS, Teoh MK, Lim TT, Tan SG . Chronic haemodialysis with PTFE arterio-venous grafts. Singapore Med J 1999;40(11):685-90.  Back to cited text no. 4    
5.Bacchini G, Del Vecchio L, Andrulli S, Pontoriero G, Locatelli F. Survival of prosthetic grafts of different materials after impairment of a native arteriovenous fistula in hemodialysis patients. ASAIO J 2001;47(1):30-3.  Back to cited text no. 5    
6.Berardinelli L. Grafts and graft materials as vascular substitutes for hemodialysis access construction. Eur J Vasc Endovasc Surg 2006;32(2):203-11.  Back to cited text no. 6    
7.Cull JD, Cull DL, Taylor SM, et al. Prosthetic thigh arteriovenous access: Outcome with SVS/AAVS reporting standards . J Vasc Surg 2004;39(2):381-6.  Back to cited text no. 7    
8.Tashjian DB, Lipkowits GS, Madden RL, et al. Safety and efficacy of femoral-based hemodialysis access grafts. J Vasc Surg 2002;35(4):691-3.  Back to cited text no. 8    
9.Taylor SM, Eaves GL, Weatherford DA, McAlhany JC Jr, Russell HE, Langan EM 3rd. Results and complication of arteriovenous access dialysis grafts in the lower extremity: A five year review. Am Surg 1996;62 (3):188-91.  Back to cited text no. 9    
10.Miller CD, Robbin ML, Barker J, Allon M. Comparison of arteriovenous graft in the thigh and upper extremities in hemo­dialysis patients. J Am Soc Nephrol 2003; 14(11):2942-7.  Back to cited text no. 10    
11.Cinat ME, Hopkins J, Wilson SE. A pros­pective Evaluation of PTFE graft patency and surveillance technique in hemodialysis access. Ann Vasc Surg 1999;13(2):191-8.  Back to cited text no. 11    
12.Modarai B, Dasgupta P, Taylor J. Follow­up of polytetrafluoroethylene arteriovenous fistulae for hemodialysis. Int J Clin Pract 2005;59(9):1005-7.  Back to cited text no. 12    
13.Huber TS, Carter JW, Carter RL, Seeger JM. Patency of autogenous and polytetra­fluoroethylene upper extremity arterio­venous hemodialysis access: A systematic review. J Vasc Surg 2003;38(5):1005-11.  Back to cited text no. 13    
14.NKF-DOQI guideline for vascular access. Am J Kidney Dis 2001:37(suppl 1):5137.  Back to cited text no. 14    
15.Chen CY, Teoh MK. Graft rescue for hemodialysis arteriovenous graft: Is it worth doing and which factors predict a good outcome? J R Coll Surg Edinb 1998;43(4):248-50.  Back to cited text no. 15    

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Correspondence Address:
Javad Salimi
Vascular Surgery Department, Sina Hospital, Hassan Abad Square, 11364 Tehran
Iran
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PMID: 18310884

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