From the Guidelines
The blood gas values (pH 7.24, pCO2 30, pO2 87, HCO3 12) indicate a mixed acidosis with both metabolic and respiratory components, as the pH is below the normal range of 7.35-7.45, and the bicarbonate level is low (1). The low pH and low bicarbonate level suggest a metabolic acidosis, while the low pCO2 suggests a respiratory alkalosis or compensation for the metabolic acidosis. However, given the low pH, it is more likely that there is a primary metabolic acidosis with a partial respiratory compensation.
- The normal pH range of the blood in humans is between 7.35 and 7.45 units, and acidosis is defined as a pH<7.35 (1).
- The body is attempting to normalize the pH by increasing ventilation to blow off CO2, which explains the low pCO2.
- The underlying cause of the metabolic acidosis could be conditions such as diarrhea, renal tubular acidosis, or early kidney injury, which would result in a normal anion gap metabolic acidosis, or it could be due to high anion gap causes such as diabetic ketoacidosis, lactic acidosis, uremia, or toxin ingestion (methanol, ethylene glycol) (1).
- Management should focus on identifying and treating the underlying cause while monitoring electrolytes and acid-base status, and severe acidosis may require sodium bicarbonate administration, but this should be done cautiously and only when the pH is dangerously low or the patient is symptomatic.
From the FDA Drug Label
Plasma concentration is regulated by the kidney through acidification of the urine when there is a deficit or by alkalinization of the urine when there is an excess. Bicarbonate anion is considered "labile" since at a proper concentration of hydrogen ion (H+) it may be converted to carbonic acid (H2CO3) and thence to its volatile form, carbon dioxide (CO2) excreted by the lung Normally a ratio of 1 :20 (carbonic acid: bicarbonate) is present in the extracellular fluid.
The given values of pH 7.24, PCO2 30, PO2 87, and bicarb 12 indicate a state of metabolic acidosis with some respiratory compensation, as the bicarbonate level is low and the PCO2 is also low, which may suggest that the body is trying to compensate for the acidosis by increasing ventilation to blow off CO2 2.
- The low bicarbonate level (12 mEq/L) is below the normal range of 24 to 31 mEq/L, indicating a metabolic acidosis.
- The pH is slightly acidic, which is consistent with the diagnosis of metabolic acidosis.
- The PCO2 is low, which may indicate some respiratory compensation for the metabolic acidosis.
It is essential to identify and treat the underlying cause of the metabolic acidosis, such as severe renal disease, uncontrolled diabetes, or circulatory insufficiency 2.
From the Research
Acid-Base Disturbance
The given values of pH 7.24, PCO2 30, PO2 87, and bicarb 12 indicate an underlying acid-base disturbance.
- The low bicarbonate level (12 mmol/L) suggests a metabolic acidosis component.
- The low PCO2 level (30 mmHg) suggests a respiratory alkalosis component.
- The pH level (7.24) is slightly acidic, which could be due to the metabolic acidosis component.
Possible Diagnosis
Based on the given values, the possible diagnosis could be a mixed acid-base disturbance, specifically a combination of metabolic acidosis and respiratory alkalosis 3.
- Metabolic acidosis is characterized by a primary reduction in serum bicarbonate concentration, which is seen in this case (bicarb 12 mmol/L) 4.
- Respiratory alkalosis is characterized by a primary decrease in PCO2, which is also seen in this case (PCO2 30 mmHg) 5.
Clinical Significance
It is essential to evaluate the clinical history and laboratory values to determine the underlying cause of the acid-base disturbance.