Should chronic metabolic acidosis be treated in older people with chronic kidney disease?

Metabolic acidosis is common in advanced chronic kidney disease, and has been associated with a range of physiological derangements of importance to the health of older people. These include associations with skeletal muscle weakness, cardiovascular risk factors, and bone and mineral disorders that may lead to fragility fractures. Although metabolic acidosis is associated with accelerated decline in kidney function, end stage renal failure is a much less common outcome in older, frail patients than cardiovascular death. Correction of metabolic acidosis using bicarbonate therapy is commonly employed, but the existing evidence is insufficient to know whether such therapy is of net benefit to older people. Bicarbonate is bulky and awkward to take, may impose additional sodium load with effects on fluid retention and blood pressure, and may cause gastrointestinal side effects. Trial data to date suggests potential benefits of bicarbonate therapy on progression of renal disease and nutrition, but trials have not as yet been published examining the effect of bicarbonate therapy across a range of domains relevant to the health of older people. Fortunately, a number of trials are now underway that should allow us to ascertain whether bicarbonate therapy can improve physical function, quality of life, vascular, bone and kidney health in older people, and hence decide whether any benefits seen outweigh adverse effects and additional treatment burden in this vulnerable group of patients.