What does an increased anion gap of 30 mmol/L indicate?

Interpretation of an Anion Gap of 30 mmol/L

An anion gap of 30 mmol/L is significantly elevated and indicates severe metabolic acidosis, most likely due to a serious underlying condition such as toxic alcohol ingestion (particularly ethylene glycol), diabetic ketoacidosis, or severe lactic acidosis that requires immediate intervention. 1

Understanding Anion Gap Values

• Normal range: The modern reference range for anion gap is 5-12 mmol/L 1, 2
• Mildly elevated: 13-20 mmol/L 2
• Moderately elevated: 20-24 mmol/L 3
• Severely elevated: >24 mmol/L (rare and clinically significant) 2
• Critical level: >28 mmol/L (indicates late ethylene glycol poisoning when in that context) 4, 1

Clinical Significance of an Anion Gap of 30 mmol/L

An anion gap of 30 mmol/L is extremely elevated and warrants immediate attention. According to the Metabolic Acidosis Guideline, an anion gap >20 mmol/L almost always signifies significant metabolic acidosis 1. Values exceeding 30 mmol/L are uncommon and may indicate either severe acidosis or laboratory error 5.

Common Causes of Severely Elevated Anion Gap (>28 mmol/L)

1. Toxic alcohol ingestion:

   • Ethylene glycol poisoning (especially with glycolate concentration >12 mmol/L) 4
   • Methanol poisoning 6

2. Severe diabetic ketoacidosis 1, 3

3. Severe lactic acidosis (shock, severe hypoxemia) 3

4. Advanced uremia (end-stage renal disease) 3

5. Salicylate poisoning (severe cases) 3

Immediate Actions for a Patient with Anion Gap of 30 mmol/L

1. Confirm the result - Consider laboratory error, especially if clinical presentation doesn't match 5, 2

2. Obtain additional laboratory tests:

   • Arterial blood gases
   • Serum lactate
   • Serum ketones
   • Blood glucose
   • Renal function tests
   • Toxicology screen (especially for toxic alcohols)
   • Osmolal gap calculation 1, 6

3. Consider toxic alcohol ingestion:

   • If ethylene glycol poisoning is suspected with an anion gap >28 mmol/L, this represents "late poisoning" and requires immediate extracorporeal treatment (ECTR) 4
   • Administer fomepizole or ethanol to block metabolism of toxic alcohols 1

4. Treat underlying cause:

   • For DKA: IV insulin infusion, fluid resuscitation, electrolyte replacement 1
   • For lactic acidosis: Improve tissue perfusion and oxygenation 1
   • For toxic alcohol ingestion: Fomepizole/ethanol and consider hemodialysis 4, 1

Important Considerations

• Mortality risk: An anion gap >28 mmol/L in ethylene glycol poisoning correlates with plasma glycolate concentration >12 mmol/L and significantly increased mortality 4

• Potential laboratory errors: Always confirm severely elevated anion gap values, as they can occasionally represent laboratory error 5, 2

• Albumin correction: Hypoalbuminemia can mask an elevated anion gap; consider albumin-corrected anion gap for accurate assessment 1, 7

• Delta ratio: Consider calculating the ΔAG/ΔHCO3 ratio to detect coexisting acid-base disorders 7

• Monitor closely: Patients with severely elevated anion gap require intensive monitoring of electrolytes, acid-base status, and organ function 1

An anion gap of 30 mmol/L represents a medical emergency requiring prompt diagnosis and intervention to address the underlying cause and prevent further morbidity and mortality.