From the Guidelines
Metabolic acidosis, a common acid-base disorder, should be managed by maintaining serum bicarbonate at or above 22 mmol/L through oral supplementation with bicarbonate salts, such as sodium bicarbonate, typically 2 to 4 g/d or 25 to 50 mEq/d, to reduce morbidity and mortality. Acid-base disorders involve abnormalities in the body's pH balance, which can lead to serious health complications if left untreated. The primary categories of acid-base disorders include metabolic acidosis, metabolic alkalosis, respiratory acidosis, and respiratory alkalosis.
Causes and Consequences
Metabolic acidosis is associated with increased oxidation of branched chain amino acids, protein degradation, and decreased albumin synthesis, as noted in a study by the National Kidney Foundation 1. This condition can be particularly problematic in individuals with chronic renal failure (CRF) or those undergoing dialysis, as it can lead to further complications such as malnutrition and increased hospitalization rates.
Diagnosis and Treatment
Diagnosis of acid-base disorders involves measuring arterial blood pH and gases, as well as assessing serum bicarbonate levels and electrolytes. Treatment depends on identifying the underlying cause and correcting the primary disorder. For metabolic acidosis, oral sodium bicarbonate supplementation is recommended to increase serum bicarbonate concentrations, with a goal of maintaining serum bicarbonate at or above 22 mmol/L 1. Higher concentrations of bicarbonate in hemodialysate (38 mmol/L) have also been shown to safely increase predialysis serum bicarbonate concentrations.
Benefits of Treatment
Correction of acidemia due to metabolic acidosis has been associated with several benefits, including increased serum albumin, decreased protein degradation rates, and increased plasma concentrations of branched chain amino acids and total essential amino acids 1. Additionally, raising serum bicarbonate levels has been linked to improved outcomes, such as fewer hospital stays and increased body weight gain.
Key Considerations
When managing acid-base disorders, it is essential to regularly monitor serum bicarbonate levels, typically at monthly intervals, and adjust treatment as needed to maintain optimal levels. By prioritizing the management of metabolic acidosis and maintaining serum bicarbonate at or above 22 mmol/L, healthcare providers can help reduce morbidity and mortality associated with acid-base disorders.
From the Research
Types of Acid-Base Disorders
- Metabolic acidosis: a condition characterized by an increase in acid or a loss of bicarbonate in the body 2, 3, 4, 5
- Metabolic alkalosis: a condition often caused by aggressive therapeutic interventions, such as volume overload, severe coagulopathy, and respiratory failure 2, 4
- Respiratory acidosis: a condition caused by decreased minute ventilation, often resulting from chronic lung disease or neuromuscular dysfunction 2, 6
- Respiratory alkalosis: a condition caused by increased minute ventilation, often resulting from sepsis, chronic liver disease, or acute pulmonary embolism 2, 4, 6
Diagnosis of Acid-Base Disorders
- The Henderson-Hasselbalch equation can be used to represent the pH of blood: pH = pK + log [HCO3-]/PCO2 3
- Measurement of the anion gap can help diagnose the cause of metabolic acidosis: (Na+ + K+) - (Cl- + HCO3-) 3, 4
- Urine anion gap calculation can be used to evaluate non-anion gap metabolic acidosis 4
- Urine chloride levels can be measured to determine the cause of metabolic alkalosis 4
Treatment of Acid-Base Disorders
- Treatment of acid-base disorders should be aimed at correcting the underlying disease process 2, 3, 4, 5
- Sodium bicarbonate may be used to treat severe metabolic acidosis, but blood pH and gases should be monitored closely to avoid overshoot alkalosis 3, 5
- Volume resuscitation and repletion of potassium deficits can be used to treat metabolic alkalosis 2
- Extracorporeal therapies may be considered in extreme cases to remove CO2 2