From the Guidelines
The correct answer is: Decreased pH, decreased HCO3, decreased PaCO2, as this set of lab values is most consistent with a simple metabolic acidosis, where the body has either lost too much bicarbonate or has an excess of acid, and the respiratory system compensates by decreasing CO2 levels [ 1 ].
Characteristic Lab Findings
In simple metabolic acidosis, laboratory findings typically include:
- Decreased serum pH (<7.35)
- Reduced serum bicarbonate (<22 mEq/L)
- Normal or compensatory decrease in PCO2
- Normal anion gap (8-12 mEq/L)
- Hyperchloremia (>107 mEq/L)
- Often normal potassium levels, though hyperkalemia may occur
Management
Management primarily focuses on treating the underlying cause, such as:
- Diarrhea
- Renal tubular acidosis
- Medication effects Sodium bicarbonate therapy (typically 50-100 mEq IV or 650 mg PO tablets 1-4 times daily) is indicated when bicarbonate levels fall below 15-18 mEq/L or in symptomatic patients [ 1 ]. Potassium supplementation may be necessary as acidosis correction can lower serum potassium. Isotonic saline should be avoided as it can worsen hyperchloremic acidosis; instead, balanced crystalloids like lactated Ringer's are preferred for fluid resuscitation. Close monitoring of electrolytes, renal function, and acid-base status is essential during treatment [ 1 ].
Underlying Pathophysiology
The underlying pathophysiology involves either excessive bicarbonate loss (as in diarrhea) or impaired renal acid excretion (as in renal tubular acidosis), leading to accumulation of chloride ions and reduction in bicarbonate concentration while maintaining a normal anion gap [ 1 ].
Note: The most recent and highest quality study [ 1 ] supports the management and characteristic lab findings of simple metabolic acidosis.
From the Research
Characteristic Lab Findings of Simple Metabolic Acidosis
- Decreased pH, indicating acidosis 2, 3, 4, 5
- Decreased HCO3-, indicating a primary reduction in serum bicarbonate concentration 2, 3, 4, 5
- Decreased PaCO2, indicating a compensatory decrease in the arterial partial pressure of carbon dioxide 2, 3, 5
Management of Simple Metabolic Acidosis
- Treatment of the underlying cause of the acidosis 2, 3, 6, 4
- Correction of the acid-base disturbance, which may involve administration of sodium bicarbonate in certain cases 2, 6, 5
- Addressing any complications or associated conditions, such as renal dysfunction or respiratory issues 2, 3, 4