From the Guidelines
Metabolic alkalosis with elevated lactic acid levels is primarily caused by the body's compensatory mechanisms to alkalosis, including increased cellular glycolysis, decreased tissue oxygen delivery, and impaired liver lactate clearance, as supported by the underlying pathophysiological principles 1.
Pathophysiological Mechanisms
- Metabolic alkalosis leads to a compensatory increase in cellular glycolysis to generate more hydrogen ions, resulting in increased lactic acid production.
- The alkalotic state causes a leftward shift of the oxyhemoglobin dissociation curve, leading to decreased tissue oxygen delivery and subsequent tissue hypoxia, which promotes anaerobic metabolism and lactic acid production.
- Alkalosis also impairs the liver's ability to clear lactate effectively, further contributing to elevated lactic acid levels.
Management Strategies
- Treating the underlying cause of metabolic alkalosis is crucial, which may involve volume repletion with normal saline for chloride-responsive cases, discontinuing offending medications, and correcting electrolyte imbalances, particularly potassium and chloride deficiencies.
- In severe cases, administration of acetazolamide may help increase renal bicarbonate excretion, while spironolactone may be beneficial for alkalosis due to excessive mineralocorticoid activity.
- Monitoring arterial blood gases, electrolytes, and lactate levels during treatment is essential to normalize pH, which will subsequently help reduce lactic acid levels by improving tissue oxygenation and hepatic lactate clearance, as implied by the principles of acid-base balance and lactate metabolism 1.
From the Research
Metabolic Alkalosis with Elevated Lactic Acid Levels
- Metabolic alkalosis is characterized by the primary elevation of serum bicarbonate and arterial pH, along with a compensatory increase in Pco2 consequent to adaptive hypoventilation 2.
- The pathogenesis of metabolic alkalosis involves either a loss of fixed acid or a net accumulation of bicarbonate within the extracellular fluid 2.
- Elevated lactic acid levels can be caused by various factors, including tissue hypoxia, alkalosis, catecholamine, and alanine transamination to pyruvate 3.
- Lactic acidosis can be classified into two types: type A, which occurs when the body must regenerate ATP without oxygen, and type B, which occurs when there is an underlying disorder that leads to lactate overproduction or underutilization 4, 5.
Causes of Metabolic Alkalosis with Elevated Lactic Acid Levels
- Metabolic alkalosis can be caused by various factors, including vomiting, aldosterone or cortisol excess, licorice ingestion, chloruretic diuretics, excess calcium alkali ingestion, and genetic diseases such as Bartter syndrome, Gitelman syndrome, and cystic fibrosis 2.
- Elevated lactic acid levels can be caused by underlying diseases such as malignancy, organ failure, cardiovascular disease, and diabetes mellitus 3.
- In some cases, metabolic alkalosis and lactic acidosis can coexist, particularly in critically ill patients 6.
Treatment and Prognosis
- Treatment of metabolic alkalosis and lactic acidosis should be aimed at the underlying source 6.
- The prognosis of patients with metabolic alkalosis and lactic acidosis is generally poor, particularly in cases with underlying organ failure or malignancy 3.
- Various treatments have been proposed for lactic acidosis, including alkalization by sodium bicarbonate, insulin-glucose-infusion, dichloroacetate therapy, and bicarbonate-buffered peritoneal dialysis 5, 3.