Hemodialysis access at initiation in the United States, 2005 to 2007: Still "Catheter First"

Despite the broad consensus that native arteriovenous fistula is the access of choice for hemodialysis, national-level information about vascular access at dialysis initiation has been unavailable in the United States. For incident hemodialysis patients, June 2005 to October 2007 (n=220,157), vascular access type was determined from the new Centers for Medicare & Medicaid Services Medical Evidence Report (form CMS-2728). Proportions with each type at first dialysis, demographic and clinical associations of each type, and associations between initial access type and survival were assessed. The mean patient age was 63.6 years; 29.4% of patients were African American, and for 44.5%, end-stage renal disease was due to diabetes. Vascular access proportions were: fistula, 13.2% of patients; graft, 4.3%; catheter/maturing fistula, 16.0%; catheter/maturing graft, 3.3%; and catheter alone, 63.2%. Adjusted odds ratios (vs. fistula) of catheter use alone were ≥1.50 for lack of insurance (1.62 [95% confidence interval 1.62–1.68]), nephrologist care for 0 to 12 months (2.75 [2.69–2.81]), other (2.19 [2.09–2.29]), or unknown (1.53 [1.44–1.63]) cause of renal disease, institutional residence (1.51 [1.45–1.57]), and 7 of 18 end-stage renal disease networks. Over a mean follow-up of 1 year, 26.0% of the study population died. Compared with fistula, adjusted mortality hazards ratios were 1.39 (1.32–1.47) for grafts, 1.49 (1.44–1.55) for catheters/maturing fistulas, 1.74 (1.65–1.84) for catheters/maturing grafts, and 2.18 (2.11–2.26) for catheters alone. While geographic variability is pronounced, vascular access at dialysis inception is typically suboptimal; suboptimal access exhibits a graded association with mortality. Lack of timely access to specialty care appears to limit optimal access.     

The flow field near a venous needle in hemodialysis: A computational study

The vascular access used in hemodialysis can suffer from numerous complications, which may lead to failure of the access, patient morbidity, and significant costs. The flow field in the region of the venous needle may be a source of damaging hemodynamics and hence adverse effects on the fistula. In this study, the venous needle flow has been considered, using three‐dimensional computational methods. Four scenarios where the venous needle flow could potentially influence dialysis treatment outcome were identified and examined: Variation of the needle placement angle (10°, 20°, 30°), variation of the blood flow rate settings (200, 300, 400 mL/min), variation of the needle depth (top, middle, bottom), and the inclusion of a back eye in the needle design. The presence of the needle has significant effect on the flow field, with different scenarios having varying influence. In general, wall shear stresses were elevated above normal physiological values, and increased presence of areas of low velocity and recirculation—indicating increased likelihood of intimal hyperplasia development—were found. Computational results showed that the presence of the venous needle in a hemodialysis fistula leads to abnormal and potentially damaging flow conditions and that optimization of needle parameters could aid in the reduction of vascular access complications. Results indicate shallow needle angles and lower blood flow rates may minimize vessel damage.