Unpleasant truths about salt restriction

Abstract

Most chronic dialysis patients are volume overloaded. This has two consequences. The first is hypertension. Even though the pathophysiologic mechanism causing this blood pressure (BP) elevation is well known, many patients are treated with antihypertensive drugs. These are often ineffective and, even if they lower BP, they do not eliminate its cause and the associated cardiac damage. But at least as harmful to the heart as the pressure load is the volume load. In the early phase of dialysis, this may lead to acute pulmonary edema, which is often erroneously referred to as "heart failure." Later, it causes dilatation of the heart compartments, stretching of their walls, and regurgitation through the valves. This dilated cardiomyopathy eventually leads to liver congestion, decreased ejection fraction, and low blood pressure. It is considered to be irreversible and incorrectly called "uremic" by many authors, but can be markedly improved and even cured by judicious ultrafiltration. This may take many months, since the heart muscle needs time to become "remodeled." All these unwanted effects could be prevented by strong dietary salt restriction. We tried to analyze why this and other "old truths" are being forgotten. While the reasons are clearly multifactorial, the unfortunate introduction of the Kt/V concept seems the most important one. The claim that adequacy of dialysis can be solely defined by urea removal, disregarding all other factors, above all salt retention, has diverted the nephrologist's attention from the most important issue, giving them the false conviction that the prescribed treatment is "adequate."