From the Research
A decreased anion gap (AGap) is typically caused by hypoalbuminemia, paraproteinemia, lithium toxicity, or multiple myeloma, and addressing the underlying cause is crucial to prevent morbidity and mortality. To address this, first identify and treat the underlying cause. For hypoalbuminemia, focus on nutritional support with protein-rich diets and possibly albumin infusions (25% albumin, 50-100ml) for severe cases 1. For paraproteinemia or multiple myeloma, consult hematology for specific treatment protocols. If lithium toxicity is suspected, discontinue lithium and provide supportive care with IV fluids. Monitor electrolytes regularly, particularly sodium, potassium, chloride, and bicarbonate, to track the anion gap. Remember that for every 1 g/dL decrease in albumin, the anion gap decreases by approximately 2.5 mEq/L.
Key Considerations
- A decreased anion gap itself is not typically dangerous but serves as an important diagnostic clue to underlying conditions that may require treatment.
- Always consider the clinical context when interpreting a decreased anion gap, as it may be a laboratory artifact in some cases.
- The normal range of the anion gap has decreased over time due to changes in measurement methodology, and a new definition for a low anion gap is in order, with an anion gap value of < 3 mEq/L considered low 1.
- Other conditions such as distal renal tubular acidosis and severe hypokalemia can also present with a decreased anion gap, and careful evaluation is necessary to prevent adverse complications 2.
- The literature on this topic highlights the importance of considering the clinical context and laboratory parameters, including urinary sodium and chloride excretion, to make an accurate diagnosis and treatment plan for patients with chronic normotensive hypokalemia 3.
Treatment Approach
- Identify and treat the underlying cause of the decreased anion gap.
- Monitor electrolytes regularly to track the anion gap.
- Consider nutritional support, albumin infusions, and consultation with hematology for specific treatment protocols as needed.
- Discontinue lithium and provide supportive care with IV fluids if lithium toxicity is suspected.
- Be aware of the potential for laboratory artifacts and consider the clinical context when interpreting a decreased anion gap.