From the Guidelines
Metabolic acidosis is the primary acid-base disturbance expected in a patient with chronic kidney disease (CKD), severe hypercreatininemia, hyperkalemia, tachypnea, vomiting, and uremic breath odor.
Key Findings
- Low serum bicarbonate concentrations in a patient with CKD almost always indicate metabolic acidosis 1
- Metabolic acidosis is associated with increased oxidation of branched chain amino acids, increased protein degradation, and decreased albumin synthesis 1
- Correction of metabolic acidemia by maintaining serum bicarbonate at or above 22 mmol/L should be a goal of the management of individuals with CKD 1
Management
- Normalization of the predialysis or stabilized serum bicarbonate concentration can be achieved by higher dialysate and/or by oral supplementation with bicarbonate salts, such as sodium bicarbonate, usually about 2 to 4 g/d or 25 to 50 mEq/d 1
- Higher concentrations of bicarbonate in hemodialysate (38 mmol/L) have been shown to safely increase predialysis serum bicarbonate concentrations 1
Clinical Implications
- Correction of metabolic acidosis has been associated with increased serum albumin, decreased protein degradation rates, and increased plasma concentrations of branched chain amino acids and total essential amino acids 1
- Raising the serum bicarbonate level has been associated with fewer hospital stays in patients with CKD 1
From the Research
Primary Acid-Base Disturbance in CKD
The primary acid-base disturbance expected in a patient with chronic kidney disease (CKD), severe hypercreatininemia, hyperkalemia, tachypnea, vomiting, and uremic breath odor is metabolic acidosis.
- Metabolic acidosis is a common complication in patients with CKD, particularly when the glomerular filtration rate (GFR) decreases to less than 20% to 25% of normal 2.
- The acidosis can be of the high-anion-gap variety, although the anion gap can be normal or only moderately increased even with stage 4 to 5 CKD 2, 3.
- The degree of acidosis approximately correlates with the severity of renal failure and is usually more severe at a lower GFR 2.
- Hyperkalemia, a common finding in CKD, can also contribute to the development of metabolic acidosis 4.
Clinical Characteristics
Clinical characteristics of metabolic acidosis in CKD include:
- Plasma bicarbonate concentrations ranging from 12 to 22 mEq/L (mmol/L) 2
- A high-anion-gap metabolic acidosis, which is associated with a higher risk of CKD progression 5
- Tachypnea, which can be a compensatory mechanism for the metabolic acidosis
- Uremic symptoms, such as fatigue, anorexia, and nausea, which are associated with alterations in circulating substances 6
Diagnosis and Treatment
Diagnosis and treatment of metabolic acidosis in CKD should take into account the patient's blood pH and serum anion gap 5.