What is metabolic acidosis?

From the Guidelines

Metabolic acidosis is a condition where the body has too much acid in the bloodstream, characterized by a blood pH below 7.35 and low bicarbonate levels, and should be treated with pharmacologic agents when bicarbonate < 18 mmol/l or if there is a clear indication to do so, with a goal to increase bicarbonate levels toward but not greater than the normal range with sodium bicarbonate or other agents 1.

Definition and Causes

Metabolic acidosis occurs when the body produces excessive acid, fails to eliminate acid properly, or loses too much bicarbonate. Common causes include kidney disease, diabetic ketoacidosis, severe diarrhea, alcohol consumption, and certain medications or toxins.

Symptoms and Treatment

Symptoms may include rapid breathing, fatigue, confusion, headache, and in severe cases, shock or coma. Treatment depends on the underlying cause but often involves addressing the primary condition, administering intravenous fluids, and sometimes providing bicarbonate supplements to neutralize excess acid. In diabetic ketoacidosis, insulin therapy is essential.

Importance of Prompt Medical Attention

The body normally maintains acid-base balance through several mechanisms including the lungs, kidneys, and buffer systems, but when these mechanisms are overwhelmed or impaired, metabolic acidosis develops. Prompt medical attention is important as severe or prolonged acidosis can damage organs and be life-threatening, and some studies suggest that correction of acidemia due to metabolic acidosis can have several benefits, including increased serum albumin, decreased protein degradation rates, and increased plasma concentrations of branched chain amino acids 1.

Key Considerations

Some key considerations in the management of metabolic acidosis include monitoring serum bicarbonate levels regularly, and using oral supplementation with bicarbonate salts or higher concentrations of bicarbonate in hemodialysate to increase predialysis serum bicarbonate concentrations 1. However, the most recent and highest quality study suggests that acidosis in adults should only be treated with pharmacologic agents when bicarbonate < 18 mmol/l or if there is a clear indication to do so 1.

• Common causes of metabolic acidosis:

• Kidney disease
• Diabetic ketoacidosis
• Severe diarrhea
• Alcohol consumption
• Certain medications or toxins

• Symptoms of metabolic acidosis:

• Rapid breathing
• Fatigue
• Confusion
• Headache
• Shock or coma (in severe cases)

• Treatment of metabolic acidosis:

• Addressing the primary condition
• Administering intravenous fluids
• Providing bicarbonate supplements to neutralize excess acid
• Insulin therapy (in diabetic ketoacidosis)

From the FDA Drug Label

Sodium Bicarbonate Injection, USP is indicated in the treatment of metabolic acidosis which may occur in severe renal disease, uncontrolled diabetes, circulatory insufficiency due to shock or severe dehydration, extracorporeal circulation of blood, cardiac arrest and severe primary lactic acidosis Treatment of metabolic acidosis should, if possible, be superimposed on measures designed to control the basic cause of the acidosis In cardiac arrest, a rapid intravenous dose of one to two 50 mL vials (44.6 to 100 mEq) may be given initially and continued at a rate of 50 mL (44. 6 to 50 mEq) every 5 to 10 minutes if necessary (as indicated by arterial pH and blood gas monitoring) to reverse the acidosis.

Metabolic acidosis is a condition that may occur in severe renal disease, uncontrolled diabetes, circulatory insufficiency due to shock or severe dehydration, extracorporeal circulation of blood, cardiac arrest, and severe primary lactic acidosis.

• It is characterized by a low total CO2 content, blood pH, and clinical condition of the patient.
• The treatment of metabolic acidosis should be superimposed on measures designed to control the basic cause of the acidosis.
• Sodium bicarbonate therapy is indicated to minimize risks inherent to the acidosis itself 2.
• The amount of bicarbonate to be given to older children and adults over a four-to-eight-hour period is approximately 2 to 5 mEq/kg of body weight - depending upon the severity of the acidosis as judged by the lowering of total CO2 content, blood pH and clinical condition of the patient 2.

From the Research

Definition of Metabolic Acidosis

• Metabolic acidosis occurs when a relative accumulation of plasma anions in excess of cations reduces plasma pH 3.
• It is characterized by a primary reduction in serum bicarbonate (HCO(3)(-)) concentration, a secondary decrease in the arterial partial pressure of carbon dioxide (PaCO(2)), and a reduction in blood pH 4.

Causes of Metabolic Acidosis

• Metabolic acidosis can occur as a result of either the accumulation of endogenous acids that consumes bicarbonate (high anion gap metabolic acidosis) or loss of bicarbonate from the gastrointestinal tract or the kidney (hyperchloremic or normal anion gap metabolic acidosis) 5.
• The cause of high anion gap metabolic acidosis includes lactic acidosis, ketoacidosis, renal failure, and intoxication with ethylene glycol, methanol, salicylate, and less commonly with pyroglutamic acid (5-oxoproline), propylene glycole, or djenkol bean (gjenkolism) 5.
• The most common causes of hyperchloremic metabolic acidosis are gastrointestinal bicarbonate loss, renal tubular acidosis, drugs-induced hyperkalemia, early renal failure, and administration of acids 5.

Diagnosis of Metabolic Acidosis

• The calculation of the serum anion gap, calculated as [Na(+)] - ([HCO(3)(-)] + [Cl(-)]), aids diagnosis by classifying the disorders into categories of normal (hyperchloremic) anion gap or elevated anion gap 4.
• Metabolic acidosis is noted in the majority of patients with chronic kidney disease (CKD) when glomerular filtration rate (GFR) decreases to less than 20% to 25% of normal 6.

Treatment of Metabolic Acidosis

• The appropriate treatment of acute metabolic acidosis, in particular organic form of acidosis such as lactic acidosis, has been very controversial 5.
• The only effective treatment for organic acidosis is cessation of acid production via improvement of tissue oxygenation 5.
• Treatment of acute organic acidosis with sodium bicarbonate failed to reduce the morbidity and mortality despite improvement in acid-base parameters 5.
• Administration of base aimed at normalization of plasma bicarbonate concentration might be associated with certain complications, such as volume overload, exacerbation of hypertension, and facilitation of vascular calcifications 6.

Adverse Effects of Metabolic Acidosis

• Adverse effects of acute metabolic acidosis primarily include decreased cardiac output, arterial dilatation with hypotension, altered oxygen delivery, decreased ATP production, predisposition to arrhythmias, and impairment of the immune response 4.
• The main adverse effects of chronic metabolic acidosis are increased muscle degradation and abnormal bone metabolism 4.
• Several adverse consequences have been associated with metabolic acidosis, including muscle wasting, bone disease, impaired growth, abnormalities in growth hormone and thyroid hormone secretion, impaired insulin sensitivity, progression of renal failure, and exacerbation of beta 2 -microglobulin accumulation 6.