Monitoring and maintenance of arteriovenous fistulae and graft function in haemodialysis patients

Effect of online haemodialysis vascular access flow evaluation and pre-emptive intervention on the frequency of access thrombosis

Introduction. Guidelines advocate surveillance of vascular access to reduce incidences of thrombosis. However, the value of online vascular access flow monitoring is still under debate.

Methods. Through a systematic literature search, the effect of online access flow surveillance combined with pre-emptive intervention on thrombosis frequency is reviewed.

Results. Due to methodological differences, adequate comparison of the individual study results is not possible. Moreover, the methodological quality of most of the included studies is not suitable for an adequate statistical analysis of the results.

Conclusion. Until now, there is no conclusive evidence that online access flow evaluation has a significant effect on the rate of thrombosis. Future large-scale studies with adequate study design, adequate surveillance and intervention protocols and, possibly, better pre-emptive intervention alternative(s) are necessary.

Relation between access blood flow and mortality in chronic hemodialysis patients

BACKGROUND

Access blood flow (Qa) measurement is a potentially important determinant of systemic hemodynamics in hemodialysis patients. High Qa may contribute to left ventricular dilation and high output heart failure. On the other hand, low Qa might lead to underdialysis, which is associated with adverse outcomes.

METHODS

In this retrospective study of incident chronic hemodialysis patients treated in three Canadian cities (Edmonton, Calgary, and Halifax), the hypothesis that extremes of Qa(low or high) would be associated with increased mortality was tested. The distribution of Qa was not Gaussian, and therefore Qa was log-transformed in analyses that treated it as a continuous variable. Qa was classified into categories defined by cutpoints of 500, 1000, 1500, and 2000 ml/min. Univariate and multivariate Cox proportional hazard models were performed to examine the relation between Qa and all-cause mortality. Patients were followed from the date of Qa measurement until death; follow-up was discontinued at loss to follow-up, kidney transplantation, or end of study.

RESULTS

Of 820 participants, those with lower levels of Qa tended to be older and to have more comorbidities. During the median follow-up period of 28 mo, 206 (25.1%) participants died and 101 (12.3%) patients received a kidney transplant. When only baseline measures of Qa were considered, there was significant association between Qa and mortality [hazard ratio (HR) per unit increase in logQa 0.81, 95% confidence interval (CI) 0.67, 0.97; adjusted HR per unit increase in logQa 0.90, 95% CI 0.72, 1.11]. The adjusted risk of mortality was similar between the different categories of baseline Qa before and after adjustment for demographic characteristics, comorbidity, and access type. In analyses that included all Qa measurements per patient as a time-varying covariate, the adjusted association between Qa and death remained nonsignificant, with no evidence of increased mortality at higher Qa (HR per unit increase in logQa 0.82, 95% CI 0.67, 1.01, P = 0.066).

CONCLUSION

The findings of this study do not suggest an increased risk of death at higher levels of Qa, Further studies would be needed to confirm an increased risk of death at lower Qa.

Vascular access for hemodialysis

Establishing and maintaining adequate vascular access is essential to providing an appropriate dialysis dose in patients with end-stage renal disease. Complications related to vascular access have a significant role in dialysis-related morbidity and mortality. The National Kidney Foundation Kidney Disease Outcomes Quality Initiative (K/DOQI) clinical practice guideline for dialysis access was last updated in 2000 and provides a framework for the optimal establishment and maintenance of dialysis access, and treatment of complications related to dialysis access. This paper reviews the 2000 K/DOQI dialysis access guideline as well as updated information published subsequently.

Access Flow in Arteriovenous Accesses by Optodilutional and Ultrasound Dilution Methods

BACKGROUND

Most large studies evaluating the diagnostic properties of access blood flow (Qa) in arteriovenous (AV) accesses have used the Transonic HD01 (Transonic Systems Inc, Ithaca, NY) device, and recommended thresholds for angiography are based on data from these studies. There has been little exploration of how the use of other devices might affect the feasibility or performance of screening in AV accesses.

METHODS

We compared 2 devices for measuring Qa: the Transonic HD01 and the Crit-Line TQA III (Hemametrics, Salt Lake City, UT). We studied 124 adults with end-stage renal disease and a functioning AV access (fistula or graft). Qa was measured with both devices in immediate succession during a single dialysis treatment. The primary outcome was the technical feasibility of the Qa measurement. We also compared mean Qa values measured by the Crit-Line III and Transonic devices.

RESULTS

Qa measurements were less likely to be technically feasible when the Crit-Line III device was used compared with the Transonic device (86.3% versus 100%; P < 0.001). In patients with valid measurements, mean Qa measured using the Crit-Line III was significantly less than that measured using the Transonic HD01 device (886 +/- 557 versus 1,148 +/- 685 mL/min; P < 0.001). The mean difference was 261 mL/min (95% confidence interval [CI], 117 to 405) and was greater at higher levels of Qa. On average, Qa measured by means of the Crit-Line III device was 73% as high as that measured using the Transonic device (95% CI, 63 to 84). There was poor agreement between devices about whether criteria for angiography were met (kappa < 0.1). The proportion of patients for whom angiography was indicated (based on results from the Crit-Line device) was significantly greater than when only results from the Transonic device were considered (40.3% versus 7.3%; P < 0.001).

CONCLUSION

Consideration should be given to device-specific Qa thresholds for angiography or, alternatively, standardization of Qa results between manufacturers. Clinicians should be aware that Qa results cannot be compared directly between different devices, and access monitoring should be performed using a single technique in any given patient. Additional studies are required before the Crit-Line TQA device can be recommended for widespread use.