El acceso vascular para hemodiálisis: la asignatura pendiente Translated title: Vascular access for haemodialysis: an unresolved issue

National guidelines promote increasing the prevalence of fistula use among hemodialysis patients. The prevalence of fistulas among hemodialysis patients reflects both national, regional, and local practice differences as well as patient-specific demographic and clinical factors. Increasing fistula prevalence requires increasing fistula placement, improving maturation of new fistulas, and enhancing long-term patency of mature fistulas for dialysis. Whether a patient receives a fistula depends on several factors: timing of referral for dialysis and vascular access, type of fistula placed, patient demographics, preference of the nephrologist, surgeon, and dialysis nurses, and vascular anatomy of the patient. Whether the placed fistula is useable for dialysis depends on additional factors, including adequacy of vessels, surgeon's experience, patient demographics, nursing skills, minimal acceptable dialysis blood flow, and attempts to revise immature fistulas. Whether a mature fistula achieves long-term patency depends on the ability to prevent and correct thrombosis. An optimal outcome is likely when there is (1) a multidisciplinary team approach to vascular access; (2) consensus about the goals among all interested parties (nephrologists, surgeons, radiologists, dialysis nurses, and patients); (3) early referral for placement of vascular access; (4) restriction of vascular access procedures to surgeons with demonstrable interest and experience; (5) routine, preoperative mapping of the patient's arteries and veins; (6) close, ongoing communication among the involved parties; and (7) prospective tracking of outcomes with continuous quality assessment. Implementing these measures is likely to increase the prevalence of fistulas in any given dialysis unit. However, differences among dialysis units are likely to persist because of differences in gender, race, and co-morbidity mix of the patient population.

Arteriovenous fistulae (AVF) have advantages over arteriovenous grafts (AVG) and central venous catheters (CVC), but whether AVF are associated independently with better survival is unclear. Recent studies showing such a survival benefit did not include early access experience or account for changes in access type over time and did not include data on some important confounders. Reported here are survival rates stratified by the type of access in use up to 3 yr after initiation of hemodialysis among 616 incident patients who were enrolled in the Choices for Healthy Outcomes in Caring for ESRD (CHOICE) Study. A total of 1084 accesses (185 AVF, 296 AVG, 603 CVC) were used for a total of 1381 person-years. At initiation, 409 (66%) patients were using a CVC, 122 (20%) were using an AVG, and 85 (14%) were using an AVF. After 6 mo, 34% were using a CVC, 40% were using an AVG, and 26% were using an AVF. Annual mortality rates were 11.7% for AVF, 14.2% for AVG, and 16.1% for CVC. Adjusted relative hazards (RH) of death compared with AVF were 1.5 (95% confidence interval, 1.0 to 2.2) for CVC and 1.2 (0.8 to 1.8) for AVG. The increased hazards associated with CVC, as compared with AVF, were stronger in men (n = 334; RH = 2.0; P = 0.01) than women (n = 282; RH = 1.0 for CVC; P = 0.92). These results strongly support existing clinical practice guidelines and suggest that the use of venous catheters should be minimized to reduce the frequency of access complications and to improve patient survival, especially among male hemodialysis patients.

Late nephrologist referral may adversely affect outcome in patients initiating maintenance hemodialysis therapy, mostly with temporary catheters that may further increase morbidity and mortality. Our aim was to evaluate the influence of 2 variables on mortality: presentation mode (planned versus unplanned) and type of access (arteriovenous fistula [AVF] versus temporary catheter) at entry. This was a 3-center, 5-year, prospective, observational, cohort study of 538 incident patients. Measurements included presentation mode, type of access, renal function and biochemical test results at entry, and stratification of risk groups. Main outcome measures were mortality and hospitalization. Of 281 planned patients (52%), 73% initiated therapy with an AVF. Of 257 unplanned patients (48%), 70% initiated therapy with a catheter (P < 0.001). Multivariate Cox analysis showed that unplanned presentation (hazard ratio [HR], 1.73; 95% confidence interval [CI], 1.23 to 2.44) and initiation of therapy with catheter (HR, 1.75; 95% CI, 1.25 to 2.46) were independently associated with greater mortality and similar HRs after adjusting for confounders. At 12 months, the number of deaths was 3 times higher in both the unplanned versus planned groups and catheter versus AVF groups. The joint effect of unplanned dialysis initiation and catheter use had an additive impact on mortality (HR, 2.89; 95% CI, 1.97 to 4.22). Greater hematocrit (HR, 1.04; 95% CI, 1.01 to 1.09) and albumin level (HR, 1.79; 95% CI, 1.37 to 2.33) showed an independent association with survival, underscoring the benefits of predialysis care. Using Poisson regression, all-cause hospitalization (incidence rate ratio, 1.56; 95% CI, 1.36 to 1.79; P < 0.001) and infection-related (incidence rate ratio, 2.62; 95% CI, 1.91 to 3.59; P < 0.001) and vascular access-related (incidence rate ratio, 1.49; 95% CI, 1.15 to 1.94; P < 0.003) admissions were higher in unplanned patients initiating therapy with a catheter than in planned patients initiating therapy with an AVF, after adjusting for confounders. Unplanned dialysis initiation and temporary catheter were independently associated with greater mortality rates in incident patients. The combined influence of both variables was associated with greater morbidity and mortality than either variable alone.