Metabolic Acidosis

What is Metabolic Acidosis ?

Metabolic acidosis-marked by excess acid accumulation and deficient base bicarbonate-is produced by an underlying disorder. Symptoms result from the body's attempts to correct the acidotic condition through compensatory mechanisms in the lungs, kidneys, and cells.

Metabolic acidosis is more prevalent among children, who are vulnerable to acid-base imbalance because their metabolic rates are faster and their ratios of water to total body weight are lower. Severe or untreated metabolic acidosis can be fatal.

Causes of Metabolic Acidosis

Metabolic acidosis usually results from excessive burning of fats in the absence of usable carbohydrates. Diabetic ketoacidosis, chronic alcoholism, malnutrition, or a low-carbohydrate, high-fat diet-all of which produce more keto acids than the metabolic process can handle-can cause this. Other causes include:

• anaerobic carbohydrate metabolism (lactic acidosis). A decrease in tissue oxygenation or perfusion (as occurs with pump failure after myocardial infarction or with pulmonary or hepatic disease, shock, or anemia) forces a shift from aerobic to anaerobic metabolism, causing a corresponding increase in lactic acid level.
• renal insufficiency and failure (renal acidosis). Underexcretion of metabolized acids or inability to conserve base bicarbonate results in excess acid accumulation or deficient base bicarbonate.
• diarrhea and intestinal malabsorption. Loss of sodium bicarbonate from the intestines causes the bicarbonate buffer system to shift to the acidic side.
• massive rhabdomyolysis. High quantities of organic acids added to the body with the breakdown of cells causes high anion gap acidosis.
• poisoning and drug toxicity. Common causative agents include salicylates, ethylene glycol, and methyl alcohol, which may produce acidbase imbalance.
• hypo aldosteronism and use of potassiumsparing diuretics. These conditions inhibit distal tubular secretion of acid and potassium.

Signs & Symptoms of Metabolic Acidosis

If metabolic acidosis becomes severe, the person may develop:

• Heart problems such as arrhythmias
• Weakness
• Shock

Exteme acidosis leads to neurological and cardiac complications:

• Neurological: lethargy, stupor, coma, seizures.
• Cardiac: arrhythmias, decreased response to epinephrine; both lead to hypotension

Diagnostic Tests

Arterial blood gas analysis reveals a pH less than 7.35 to confirm metabolic acidosis, decreased partial pressure of carbon dioxide as part of the compensatory mechanism, and bicarbonate levels less than 24 mEq/L in acute metabolic acidosis.

Urine pH is 4.5 in the absence of renal disease.

Serum potassium levels are usually elevated, as hydrogen ions move into the cells and potassium moves out of the cells to maintain lectroneutrality.

Blood glucose levels increase in diabetes. Serum ketone body levels increase in diabetes mellitus.

Plasma lactic acid levels are elevated in lactic acidosis.

Treatment

For acute metabolic acidosis, treatment may include I.V. administration of sodium bicarbonate (when arterial pH is less than 7.2) to neutralize blood acidity. For chronic metabolic acidosis, oral bicarbonate may be given. Other treatment measures include careful evaluation and correction of electrolyte imbalances and, ultimately, correction of the underlying cause. For example, diabetic ketoacidosis requires insulin administration and fluid replacement.

Prevention Tips

Keeping diabetes mellitus type I under control can avoid many cases of metabolic acidosis. Avoid ingesting toxic materials.