Sodium fluid relationship hemodialysis

sodium fluid relationship hemodialysis

Fluid shifts during hemodialysis involve changes in both extracellular and intracellular volumes. This study aimed to determine the effect of intradialytic sodium. Inability to excrete salt with consequent expansion of extracellular fluid volume is . Most sodium removal with both dialysis modalities is convective through .. Relations between malnutrition-inflammation-atherosclerosis and volume status. The primary role of maintenance hemodialysis (HD) is the extracellular fluid volume . In another, a relationship was found between the Na+ gradient and the .

Sodium Balance in Maintenance Hemodialysis

It is very difficult indeed for a conscious patient to ignore thirst, and severe thirst will drive a patient to find fluid wherever they can—for example, drinking the water from the flower vase. Using hypertonic saline infusions, Argent et al.

It follows that no dialysis patient whose sodium intake exceeds sodium output will be able to resist the stimulus to drink to maintain serum osmolality within the normal range, unless first rendered unconscious! Two things follow from this simple argument. 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, because they are being made to feel guilty and inadequate at being unable to restrict their fluid intake—and is a waste of time.

However, this may not be the whole story: Hypovolaemia can also stimulate thirst, of course, so inappropriately low target weights might cause thirst as well as increased appetite for salt. This is probably less much common as a cause for thirst than salt overload. What is the impact of dialysate sodium? Regression of left ventricular hypertrophy has also been reported [ 26 ]. Such a policy would reduce unnecessary thirst, weight gain, and hypertension caused by dialysing sodium into patients.

In peritoneal dialysis too, low sodium dialysate results in reduction in blood pressure [ 28 ]. Sodium profiling during dialysis has been promoted as a way of improving cardiovascular stability during dialysis without causing net sodium gain.

sodium fluid relationship hemodialysis

However, this assumption has never been tested adequately. It is quite possible, for instance, that high extracellular fluid sodium concentration results in flux of water from cells.

This results in intracellular dehydration, which might then cause rebound hypernatraemia after completion of dialysis, which might explain why some sodium profiled patients appear to become more thirsty, resulting in a vicious cycle of increasing fluid gains and increasing symptoms during rapid volume removal on dialysis.

How else may sodium overload influence blood pressure? One of the intriguing observations in patients undergoing long slow dialysis at Tassin, where blood pressure is nearly universally controlled with salt restriction and fluid removal on dialysis [ 30 ], is that compared with patients undergoing standard dialysis, peripheral vascular resistance is low—whereas one might expect a higher peripheral vascular resistance as a result of vasoconstriction in response to relative extracellular volume depletion [ 31 ].

The cause of this paradoxical vasodilatation is not certain. It may relate to a more efficient removal during long slow dialysis of vasconstrictor substances, although these have not been identified. Water ingested without sodium will distribute throughout total body water, and will, therefore, have much less impact on extracellular volume. The water load would cause a small drop in extracellular sodium concentration. This would result in a greater osmotic gradient between dialysate and plasma during dialysis, favouring rapid removal of the extra water.

Sodium Balance in Maintenance Hemodialysis

Theoretically, a high water load could result in hyponatraemia, and the increased cell volume caused by water entering cells could cause cerebral oedema. Some advice to avoid excessive water intake would, therefore, remain necessary. One small prospective randomized controlled trial has examined this strategy: During the low sodium diet, weight gains were significantly lower, despite free fluid intake, than on the standard diet [ 34 ].

Where is the catch?

Chronic Kidney Disease (CKD) Pathophysiology

The drawback to this argument is the practical difficulty of persuading patients to limit dietary sodium intake. The skin is a highly vascularized organs and consists mainly of extracellular matrix of high glycosaminoglycan GAG content.

In rats, a high salt diet was found to lead to increased skin GAG content 9 and pronounced skin GAG sulfation 8which resulted in an increase in negative GAG charge density. First, it contributes to the persistence of hypertension. Within the few days following isotonic saline infusion, ECV, blood volume, and cardiac output decreased, but total peripheral resistance increased and BP remained elevated Second, the third compartment seems to be related to delayed decreases in BP after ECV normalization the lag phenomenon.

The preliminary results showed a trend of predialysis weight and blood pressure reduction In Keen et al, the historic value was computed from monthly routine laboratory data for every patient over an observation period ranging from 9 to 16 months These historic value had a coefficient of variation of only 1.

Similarly, Rainmann et al. Additional technical and physiological aspects should also be considered. The most commonly used method is indirect ionometry, which involves diluting plasma by 1: Mathematically, this is done as follows 24 Adjusted Serum Sodium The adjustment proposed by Gotch et al 26 does not consider the lipid contribution to void volume. Thus, in the presence of hyperlipidemia, the algorithm by Waugh 27 may be more precise.

Katz proposed a correction factor of Furthermore, a linear approach in chronic maintenance HD patients suggested a correction factor of Yet more questions regarding how to align incident HD patients immediately after initiating dialysis, the effects of seasonality, and the effects of comorbidities remain to be answered.

Footnotes The author has nothing to disclose.

Fluid dynamics during hemodialysis in relationship to sodium gradient between dialysate and plasma.

Sodium balance in maintenance hemodialysis. Dialysis unphysiology and sodium balance. Fluid balance, dry weight, and blood pressure in dialysis. Sodium, hypertension, and an explanation of the "lag phenomenon" in hemodialysis patients.

sodium fluid relationship hemodialysis

Hypertension in end-stage renal disease. N Engl J Med.

Am J Physiol Renal Physiol. Internal sodium balance in DOCA-salt rats: Kidneys and fluids in pressure regulation. Small volume but large pressure changes.

Fluid dynamics during hemodialysis in relationship to sodium gradient between dialysate and plasma.

Penne EL, Sergeyeva O. Sodium flux and dialysate sodium in hemodialysis. Petitclerc T, Jacobs C. What is optimal and can it be individualized?

The association of the sodium 'setpoint' to interdialytic weight gain and blood pressure in hemodialysis patients.