Cardiovascular stability during haemodialysis, haemofiltration and haemodiafiltration (original) (raw)

2000, Nephrology Dialysis Transplantation

Several comparative studies have claimed frequent acute complication occurring during haemothat procedures based substantially or exclusively on dialysis (HD) treatment. The importance of this compressure-driven water-solute transport, such as haemoplication cannot be overemphasized, because it can diafiltration or haemofiltration, afford better protecmarkedly impair patients' well-being in both the shorttion of the cardiovascular tolerance to fluid removal and long-term, and eventually impact strongly on than conventional haemodialysis. survival. Thus, it is quite understandable that many During each depurative modality, several factors are people working in the dialysis field have been, and still set in motion that might impact, each in its own right, are, deeply engaged in preventing this fearful complicaupon the haemodynamic response to fluid withdrawal. tion. As has happened often in the history of medical To explore the haemodynamic effect of each of them progress, it was a serendipitious observation that led singularly, one needs to keep all other components to the discovery that blood ultrafiltration, when separunvaried. However, this is very difficult to accomplish. ated in time from blood dialysis, affords better protec-For instance, to confirm the alleged greater protection tion of haemodynamic stability than when the two of cardiovascular stability by pure convection vs procedures, as per routine practice, are carried out diffusion, one needs to keep unvaried all the other simultaneously [1]. Several studies, carried out subfactors potentially affecting haemodynamic tolerance, sequently, reinforced the belief that procedures based i.e. the rate of body fluid removal, the membrane, the on convective transport are superior to those based buffer, the blood temperature in the extracorporeal mainly on diffusive transport in protecting the stability circuit, depuration efficiency, the sodium balance, the of blood pressure and heart rate [2-6 ]. This belief fluid sterility and so on. Such studies are still awaited. helped persuade many doctors, at least in several However, clinical trials published to date have not western European countries, to adopt haemofiltration resolved the question of whether haemofiltration and (HF) or haemodiafiltration (HDF) as procedures of haemodiafiltration provide a better haemodynamic tolfirst choice in the treatment of patients at risk for erance to fluid removal. If we limit our consideration recurrent dialysis hypotension. Strong support in to controlled trials only, most prospective studies have favour of the new depurative technique came from a adopted a cross-over design implemented on very small series of haemodynamic studies showing that, for equal patient samples and for very short periods. Such an amounts of fluid removed, HF elicited an appropriate approach is liable to generate misleading results because the incidence of dialysis hypotension often increase in peripheral vascular resistance, whereas fluctuates from time to time. Owing to such fluctustandard HD failed to do so [7]. The better tolerance ations, results can be strongly affected by the 'order to HF than to HD was apparently not related to effect' of the cross-over from one technique to the differences in sodium balance, type of buffer used in other. The negative results provided by parallel comthe dialysate or infusate, rate of solute removal or parisons of procedures should be taken with caution membrane type [8,9]. Having ruled out all these elebecause patients samples did not include a suitable ments as vascular destabilizers, Shaldon et al. hypoproportion of unstable patients. thized that the dialysate itself must be 'the' vascular destabilizer. Actually, they worked out the interleukin hypothesis, in an attempt to elaborate a series of