It is often associated with poor prognosis, with a mortality rate as high as 57% if the pH remains untreated at 7.20. At lower pH levels, acute metabolic acidosis can lead to impaired circulation and end organ function. Chronic Metabolic Acidosis
Chronic metabolic acidosis commonly occurs in people with Chronic Kidney Disease with an eGFR of less than 45 ml/min/1.73m2, most often with mild to moderate severity; however, metabolic acidosis can manifest earlier on in the course of Chronic Kidney Disease. Multiple animal and human studies have shown that metabolic acidosis in Chronic Kidney Disease, given its chronic nature, has a profound adverse impact on cellular function, overall contributing to high morbidities in patients. The most adverse consequences of chronic metabolic acidosis in people with Chronic Kidney Disease and in particular, for those who have end-stage renal disease (ESRD), are detrimental changes to the bones and muscles. Acid buffering leads to loss of bone density, resulting in an increased risk of bone fractures, renal osteodystrophy, and bone disease; as well, increased protein catabolism leads to muscle wasting. Furthermore, metabolic acidosis in Chronic Kidney Disease is also associated with a reduction in eGFR; it is both a complication of Chronic Kidney Disease, as well as an underlying cause of Chronic Kidney Disease progression. Treatment
Treatment of metabolic acidosis depends on the underlying cause, and should target reversing the main process. When considering course of treatment, it is important to distinguish between acute versus chronic forms.
Acute Metabolic Acidosis
Bicarbonate therapy is generally administered In patients with severe acute acidemia (pH < 7.11), or with less severe acidemia (pH 7.1-7.2) who have severe acute kidney injury. Bicarbonate therapy is not recommended for people with less severe acidosis (pH ≥ 7.1), unless severe acute kidney injury is present. In the BICAR-ICU trial, bicarbonate therapy for maintaining a pH >7.3 had no overall effect on the composite outcome of all-cause mortality and the presence of at least one organ failure at day 7. However, amongst the sub-group of patients with severe acute kidney injury, bicarbonate therapy significantly decreased the primary composite outcome, and 28-day mortality, along with the need for dialysis. Chronic Metabolic Acidosis
For people with Chronic Kidney Disease, treating metabolic acidosis slows the progression of chronic kidney disease. Dietary interventions for treatment of chronic metabolic acidosis include base-inducing fruits and vegetables that assist with reducing the urine net acid excretion, and increase TCO2. Recent research has also suggested that dietary protein restriction, through ketoanalogue-supplemented vegetarian very low protein diets are also a nutritionally safe option for correction of metabolic acidosis in people with Chronic Kidney Disease.Currently, the most commonly used treatment for chronic metabolic acidosis is oral bicarbonate. The NKF/KDOQI guidelines recommend starting treatment when serum bicarbonate levels are <22 mEq/L, in order to maintain levels ≥ 22 mEq/L.