Sodium Tolerance in CKD with Metabolic Acidosis: Does the Anion Matter?

While patients with chronic kidney disease
(CKD) produce endogenous acids, they also experience a reduction in net acid
excretion, causing a primary decrease in serum bicarbonate concentration:
chronic metabolic acidosis. Results of prospective studies and retrospective
cohort analyses suggest an association between higher risk for progression of
CKD in the presence of untreated metabolic acidosis.

Sodium bicarbonate (NaHCO₃) or
sodium citrate are commonly used to normalize serum bicarbonate levels in
academic patients; both agents have been shown to slow CKD progression.
However, according to David A. Bushinsky, MD, the John J. Kuiper
Distinguished Professor of Medicine and of Pharmacology and Physiology,
University of Rochester School of Medicine and Dentistry, Rochester, New York,
studies using that approach have routinely excluded patients with common
sodium-sensitive comorbidities, including poorly controlled hypertension,
congestive heart failure, volume overload, or edema.

In the American Journal of Kidney Diseases,
Dr. Bushinsky reported on the effect of the anion that accompanies sodium
delivered with those therapies [2019;73(6):858-865]. In the report, he sought to
determine whether there is a difference in the negative effects on blood
pressure and sodium retention, measured by an increase in edema, weight gain,
and congestive heart failure, seen with oral administration of sodium chloride (NaCl)
when a similar amount of sodium is given with bicarbonate or citrate in
patients with CKD and metabolic acidosis.

Results of a literature review suggest that
neither blood pressure nor sodium retention are increased when NaHCO₃
is administered to patients with CKD and a concurrent severe NaCl dietary
restriction (~10 mEq/d). However, such severe NaCl restriction is feasible only
under control in clinical research environments. Conversely, when NaHCO₃ is
administered to patients without severe dietary NaCl restriction, there is an
increase in blood pressure and sodium retention.

“Thus, unless patients with CKD can tolerate a
diet virtually devoid of NaCl, additional sodium, regardless of the
accompanying anion, appears to increase blood pressure and sodium retention,”
Dr. Bushinsky said.