By Peter Laird, MD
Gary Peterson of RenalWeb listed an important confirmatory study from the Canadian Medical Association Journal on the timing of dialysis initiation and remaining residual renal function. This is the second major study looking at the issue of early initiation of dialysis that not only shows no benefit, but actual harm may occur with this strategy. The IDEAL study recently published in the NEJM revealed no benefit of early dialysis. The CMAJ article available in full .pdf delves into some of the putative reasons why those with preserved renal function at onset of dialysis may actually be at higher risk. Ultrafiltration practices may be at the center of this debate:
Association between estimated glomerular filtration rate at initiation of dialysis and mortality
A nonsignificant increase in cardiovascular deaths in the early-initiation group was observed in both this study and the IDEAL trial. Sudden cardiac death is the most common cause of death among patients undergoing hemodialysis,and some researchers have suggested that sudden cardiac death may be precipitated by the dialysis procedure itself. Patients with higher residual renal function have less intradialytic weight gain because clearance is preserved, and they may be at greater risk for hypotension because of ultrafiltration from the dialysis. The increased risk of hypotension with its attendant effect on cardiac ischemia, combined with myocardial stunning, could contribute to increased mortality among patients with initiation of dialysis at higher levels of estimated glomerular filtration rate. Consistent with this hypothesis, Termorshuizen and coworkers found that excess ultrafiltration in relation to intra-dialytic weight gain was associated with increased mortality.
Sadly, I have read on IHD several patients complaining that their dialysis techs and nurses ignore their complaints that the ultrafiltration rates are too excessive and instead simply brand them as difficult patients. Yet the evidence mounts that excessive ultrafiltration rates are deadly causing myocardial ischemia (lack of oxygen and blood flow to the heart) leading to scarring of the heart called fibrosis. The precise cause of the the increased mortality associated with early initiation remains unproven and the discussion above at this point is speculative. The take home message is that the clinical presentation is a stronger indicator of the need for dialysis initiation than simply an arbitrary GFR level.
The FHN defined optimal dialysis strategy as more frequent and longer duration, yet again, the mechanics of dialysis and ultrafiltration rates, potassium levels in dialysate, blood pump speed, ultra-pure dialysate, avoiding reuse all are areas of further research with much evidence to date that we need to modify our dialysis practices to avoid what appear to be iatrogenic complications of dialysis. It is time to enter into a period of reevaluating optimal dialysis practices and implementing the best survival strategies for the benefit of all needing this life saving renal replacement alternative.
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