Advice From The Kidney Doctor

In this article of Be Healthy, Be Happy, I’d like to discuss an issue that comes up every day in the dialysis center: fluid restriction. There is no doubt that fluid intake is the most important determinant of weight gain between one session of hemodialysis and the next, particularly in patients with minimal urine output. However, we must be careful not to neglect the importance of dietary sodium intake as well. Patients drink for one of two reasons: thirst, and because they ‘feel like a drink’ – for example, social drinking. It is very difficult for a conscious patient to ignore thirst, and severe thirst will drive a patient to find fluid wherever they can. When patients do this, it is not because they are ‘mad’, ‘totally non-compliant’ or ‘too stupid to understand the importance of fluid restriction’ – it is because it is nearly impossible to ignore such a strong physiological stimulus. The over-riding stimulus to thirst is sodium concentration. Thus, we should concentrate on advising and helping dialysis patients to limit their salt intake, which will help limit thirst. Advising dialysis patients to restrict fluid intake when they have not had advice on how to limit their salt intake is inhumane, and is a waste of time. What other factors may impact thirst and fluid gains? A certain amount of sodium is delivered to each patient during each dialysis session. This may be prescribed by your nephrologist to help keep your blood pressure from dropping. If you’re caught in a vicious cycle of increasing fluid gains and increasing symptoms during rapid fluid removal on dialysis, talk to your nephrologist about your ‘sodium profile’ and how this can be changed to promote less thirst. There’s also some evidence that ACE inhibitors, a certain class of blood pressure medication, can reduce thirst and weight gain in dialysis patients with habitually high inter-dialytic weight gain and fluid overload.

In summary, a low sodium diet with advice to drink only when thirsty has been shown in clinical trials to significantly limit weight gains. The hard part then becomes the practical difficulty of persuading patients to limit dietary sodium intake. The high sodium content of many processed foods means that simply avoiding salt at the table and in cooking will not be enough to achieve these effects. However, any reduction in salt intake is likely to have a beneficial effect in the right direction. Talk to your dietician about the possible sources of sodium in your diet, and ways to lower it. And then maybe you won’t raise as many eyebrows when you get on the scale!

Dr. Christopher Caputo
Queens Nassau Nephrology Services