In group B, fewer hypotensive episodes were recorded (24 out of 72 in group B vs. 59 out of 72 in group A). Saline infusion was required in 57 cases in group A and 15 cases in group B. Urea Kt/V was 1.34 +/- 0.08 in group A and was 1.26 +/- 0.06 in group B; eKt/V was much higher in group B (1.12 +/- 0.05) than in group A (1.03 +/- 008). A significantly higher rebound was observed in group A (14.2 +/- 2.7%) compared with group B (6.4 +/- 2.3%). Discussion. A greater solute sequestration seems to occur during hemodialysis with hypotension. This results in lower eKt/V, enhanced postdialytic rebound, and lower solute removal. Higher efficiency can be observed when dialysis is carried out smoothly and cardiovascular stability is maintained. We conclude that new systems for blood volume monitoring and automatic biofeedback may not only reduce the number of hypotensive episodes during dialysis, but may also contribute to significantly increase the efficacy of the treatment.
Ultrafiltration and pressure profiles in hollow fiber dialyzers with different hydraulic permeabilities have been investigated with a new scintigraphic method. Radiolabelled albumin macroaggregates, used as a nondiffusible marker molecule, were added to the blood in an in vitro circuit and circulated through cuprophan and polysulphon dialyzers. Since the marker molecule was too big to cross the dialysis membrane, its changes in concentration were assumed to occur in response to the variation of the blood water content (filtration or back-filtration). These changes in concentration, recorded by a gamma camera, were evaluated to establish the cumulative values of filtration and back-filtration and their relevant profiles along the length of the dialyzer. The achieved data were compared with the experimental values of ultrafiltration empirically measured and with the theoretical values predicted by a classic linear method. Two conditions were analyzed: A) the minimal filtration rate necessary to avoid back-filtration (critical filtration); and B) the condition of zero net filtration in which filtration equals back-filtration. The nuclear method proved to be extremely precise in predicting the ultrafiltration values and significantly more precise than the linear method, especially for the highly permeable dialyzer. The reason for that probably depends on the non-linear pressure and ultrafiltration profile observed with the scintigraphic pattern of the dialyzer. Viscosity changes and local variations in blood flow may in fact interfere with the pressure drop inside the hollow fibers and result in such a complex behavior. The other interesting aspect of this method is the possibility of accurate measurement of the amount of back-filtration that wouldn't be possible with simple calculations. In conclusion, the complex nature of the phenomena regulating the water fluxes in hollow fiber dialyzers requires more complex calculation than a simple linear model to achieve an accurate range of predictability.
The epidemiology of acute renal failure (ARF) has recently displayed an increasing shift of cases from the renal ward to the intensive care unit (ICU). Accordingly, two groups of physicians are now highly involved focus on speci®c aspects such as cytokine removal and physiological response to continuous versus intermittent therapies. We hope that little by little these studies will contribute towards piecing together the overall picture.
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