Post-dilution hemodiafiltration with a heparin-grafted polyacrylonitrile membrane.

The aim of this multicenter, prospective study was to explore the possibility of carrying out routine sessions of post-dilution hemodiafiltration with a polyacrylonitrile membrane grafted with heparin (HeprAN) and reduced anticoagulation. Forty-four patients from eight centers were included in the study and treated by means of post-dilution on-line hemodiafiltration with automatic control of TMP, according to three different modalities tested consecutively: phase 1, polyethersulfone filter primed with heparinized saline and anticoagulated with continuous infusion of unfractionated heparin 1000/h; phase 2, HeprAN membrane filter primed with saline without heparin. Anticoagulation: a 1000-unit bolus of unfractionated heparin at the start of session followed by a second one at the end of the second dialysis hour; phase 3, same filter and priming procedure as in phase 2; anticoagulation with nadroparin calcium at the beginning of treatment. Partial or massive clotting of the dialyzer occurred in less than 1% of sessions in phase 1; 10% and 7% in phase 2; and 1% and 2% in phase 3. Clotting limited to the drip chambers was observed in 13%, 34% and 12%, respectively. The study of coagulation parameters showed a better profile when low-molecular weight heparin (LMWH) was used in association with HeprAN membrane, while the generation of TAT complexes did not differ from that observed with the standard anticoagulation modality used in phase 1. Our results suggest that the HeprAN membrane can be used safely in routine post-dilution hemodiafiltration with reduced doses of LMWH.

Cardiac response to hemodialysis with different cardiovascular tolerance: heart rate variability and QT interval analysis.

A therapy-specific worsening of cardiovascular stability during bicarbonate dialysis (BD) with respect to acetate-free biofiltration (AFB) have been previously reported. We further investigated the impact of the 2 therapies on electrocardiographic parameters in order to gain novel insight into the cardiac responses. Holter ECG acquired during hypotension-free sessions (12 BD + 12 AFB) were retrospectively analyzed. R-R intervals were extracted from ECG recordings. An autoregressive spectral technique was used to compute low- and high-frequency (LF and HF) components of heart rate variability (HRV). QT interval duration was measured with a computer-assisted technique and corrected for HR. In BD the LF component of HRV after an initial increase was slowly depressed with respect to AFB (p < 0.05). QT duration showed a significant (p < 0.01) hemodialysis-induced reduction. QT shortening was more pronounced (p < 0.05) in BD than in AFB (-31 vs. -10 ms), even after correction for HR (p < 0.05). Cardiac electrical activity is significantly affected by the hemodialysis technique. The decrease in the LF component of HRV and the QT shortening are coherent with the worse cardiovascular tolerance observed in BD and with the hypothesis of an enhanced production of endogenous nitric oxide.

Model-based study of the effects of the hemodialysis technique on the compensatory response to hypovolemia.

BACKGROUND: Hemodialysis technique (dialysate composition, filter, convection/diffusion ratio, etc.) can have an impact on the patient's tendency to acute hypotension. We have examined the hypothesis that the dialysis technique affects the hypotension risk by altering the cardiovascular compensatory response to hemodialysis-induced hypovolemia. METHODS: Twelve hypotension-prone subjects were studied during six sessions of conventional bicarbonate dialysis (BD) and six sessions of acetate-free biofiltration (AFB). Blood volume (BV) control system was used in AFB to provide a BV change equivalent to the BV change observed in BD. The efficacy of reflex compensatory mechanisms was assessed by a model-based computer analysis of the BD and AFB sessions. RESULTS: BD sessions were complicated by hypotension more frequently than the AFB ones (34/66 BD vs. 18/66 AFB). Hypotension arose about 60 minutes earlier in BD (123 +/- 41 minutes in BD vs. 183 +/- 25 minutes in AFB, P < 0.01), and after a smaller BV reduction (hypotension BV 7.9%+/- 2.0% in BD vs. 10.9%+/- 2.6% in AFB, P < 0.05). Model-based computer analysis of the sessions without hypotension revealed differences in peripheral resistance adaptation (9%+/- 9% BD vs. 19%+/- 7% AFB, P < 0.05) as well as in the stroke volume reduction (19%+/- 8% BD vs. 10%+/- 8% AFB, P < 0.001). Model analysis of sessions with hypotension indicated that compensatory mechanisms were almost inoperative in BD, whereas a residual capacity to control peripheral resistance and cardiac contractility was present in AFB. Model simulations demonstrated that hypotension occurred later in AFB since the residual compensatory capacity in AFB was able to sustain the arterial pressure for larger BV reductions (8.3% BD vs. 11.2% AFB). CONCLUSION: The increased risk of acute hypotension in BD compared to AFB is caused by a therapy-induced inhibition of reflex compensatory response to hypovolemia.