Pharmacologic prevention of vascular access stenosis

Effects of aspirin resistance and mean platelet volume on vascular access failure in hemodialysis patients

BACKGROUND/AIMS

Maintaining the patency of vascular access (VA) in hemodialysis (HD) patients is important and can be life-saving. We investigated the effects of aspirin resistance and mean platelet volume (MPV) on VA failure in HD patients.

METHODS

We enrolled 163 patients on maintenance HD. VA failure was defined as thrombosis or a decrease of > 50% of the normal vessel diameter, as revealed by angiography.

RESULTS

Aspirin resistance was observed in 17 of 109 patients in whom this parameter was measured, and was not significantly associated with VA failure (p = 0.051). The mean MPV was 9.15 ± 0.05 fL. The 163 patients were grouped by the median MPV value (9.08 fL) at baseline; patients with higher MPVs (n = 82) had lower platelet counts (p = 0.002) and albumin levels (p = 0.009). During 34 months of follow-up, 65 VA failures (39.9%) occurred. The Kaplan-Meier curve revealed significant differences between the two groups in terms of cumulative VA failure (54.1% vs. 35.3%, p = 0.018). On multivariate analysis, the MPV (hazard ratio [HR], 1.794; 95% confidence interval [CI], 1.066 to 3.020; p = 0.028), platelet count (HR, 1.003; 95% CI, 1.001 to 1.006; p = 0.01), and smoking status (HR, 1.894; 95% CI, 1.019 to 3.519; p = 0.043) independently predicted VA failure.

CONCLUSION

A high MPV was associated with an increased risk of VA failure, whereas aspirin resistance showed only a weak association. The MPV may predict VA survival in HD patients.

Oral prostacycline analog and clopidogrel combination provides early maturation and long-term survival after arteriovenous fistula creation: A randomized controlled study

Vascular access is used as a lifeline for hemodialysis in patients with end stage renal disease failure (ESRD). Failure of arteriovenous fistula (AVF) maturation is still high. The purpose of this study was to research the effects of clopidogrel in combination with oral iloprost, a synthetic analog of prostacyclin PGI2. Ninety-six diabetic ESRD patients were divided into two groups. In the first group (Group 1, N = 50), clopidogrel (75 mg daily dose) and an oral prostacycline analog (200 mg daily dose) were administered. In the second group (Group 2, N = 46), placebo was given. All patients took study medication 7-10 days prior to surgery. A Doppler ultrasound (USG) was performed for measurement of arterial and venous diameters, and peak systolic velocity of arterial flow based on subsequent fistula adequacy. Autogenous AVFs were constructed in forearm as distally as possible in all patients. Both groups were followed-up for a year. In the placebo group, early AVF thrombosis was detected in two patients (4.3%). AVF maturation failure was noted in 14 patients (30.4%) in placebo group and in four patients (8%) in clopidogrel plus oral prostacycline analog group in the early postoperative period (P = 0.001). The mean maturation time was 38 ± 6.5 and 53 ± 12.8 days in study and placebo groups, respectively (P = 0.023). The mean blood flow was 352 ± 94 mL/min in placebo group and 604 ± 125 mL/min in study group (P = 0.001). The arterial end diastolic velocity was 116 ± 14 cm/s in study group and 72 ± 21 cm/s in placebo group (P = 0.036) 1 year after the surgery. Our data indicated that clopidogrel and oral prostacycline analog combination is effective and safe for the prevention of primary AVF failure in hemodialysis patients and decreased acute and chronic thrombotic events.

Consistent aspirin use associated with improved arteriovenous fistula survival among incident hemodialysis patients in the dialysis outcomes and practice patterns study

BACKGROUND AND OBJECTIVES

The relationship between aspirin use and arteriovenous fistula (AVF) survival has been lacking. The aim of this study was to evaluate the association between AVF survival and aspirin use.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Data on 2815 incident hemodialysis patients (on dialysis <or= 30 d) using an AVF at enrollment into the Dialysis Outcomes and Practice Patterns Study between 1996 and 2004 were analyzed. Cox regression was used to examine the association between aspirin use and the risk of final AVF failure, first AVF failure, and a gastrointestinal bleeding event. Aspirin use was determined at baseline and one year later. Patients using aspirin at baseline and one year later were considered consistent aspirin users. All models accounted for facility clustering effects and were adjusted for age, race, gender, body mass index, prior permanent access failure, prior placement of a catheter, 10 comorbid conditions, laboratory data, and other medications, and stratified by regions.

RESULTS

Consistent aspirin use was significantly related to a lower risk of final AVF failure. Facility-level analysis, which may reduce confounding by indication, also showed a nearly significant trend of reduced risk of final AVF failure with greater prevalence of consistent aspirin use within dialysis facilities (P for trend = 0.07). The occurrence of a new gastrointestinal bleeding event during the study period was not associated with aspirin use.

CONCLUSIONS

These results suggest that consistent aspirin use may be beneficial for AVF survival among incident hemodialysis patients.

Association between vascular access failure and the use of specific drugs: the Dialysis Outcomes and Practice Patterns Study (DOPPS)

BACKGROUND

Several drugs have been proposed to improve vascular access patency based on favorable anticoagulant, antiplatelet, or vascular-remodeling properties. However, there is little evidence to guide drug strategies.

METHODS

The association between vascular access patency and the use of specific drugs was studied in a large sample of US hemodialysis patients enrolled in the Dialysis Outcomes and Practice Patterns Study, an international, prospective, observational study. In general, it was assumed that the drugs were prescribed for indications unrelated to vascular access preservation. Primary (unassisted survival) and secondary vascular access patency (assisted survival) were modeled using Cox regression (time to failure) adjusted for age, sex, race, body mass index, incidence to end-stage renal disease, diabetes mellitus, hypertension, valvular disease, chronic obstructive pulmonary disease, aortic aneurysm, deep-vein thrombosis, number of previous permanent accesses, and facility-clustering effects. Fistulae (n = 900) and grafts (n = 1,944) were evaluated separately. Technical failures within the first 30 days of surgical placement were excluded from the analysis.

RESULTS

Treatment with calcium channel blockers was associated with improved primary graft patency (relative risk [RR] for failure, 0.86; P = 0.034). Aspirin therapy was associated with better secondary graft patency (RR, 0.70; P < 0.001). Treatment with angiotensin-converting enzyme inhibitors was associated with significantly better secondary fistula patency (RR, 0.56; P = 0.010). Patients administered warfarin showed worse primary graft patency (RR, 1.33; P = 0.037).

CONCLUSION

These findings should help guide clinical trial priorities toward vascular access preservation using one or more of the agents that show significant risk reduction for access failure in this study.