Is it reasonable to check lactic acid levels when assessing a diabetic patient for diabetic ketoacidosis (DKA)?

Lactic Acid Testing in Diabetic Ketoacidosis Assessment

Yes, it is reasonable to check lactic acid levels when assessing a diabetic patient for DKA, as lactic acidosis can coexist with or mimic DKA, contributing to the anion gap metabolic acidosis. 1, 2

Rationale for Lactic Acid Testing in DKA

Lactic acid measurement is justified for several key reasons:

1. Differential diagnosis of high anion gap metabolic acidosis:

   • DKA must be distinguished from other causes of high anion gap metabolic acidosis, including lactic acidosis 1
   • Blood lactate measurement helps differentiate between various causes of metabolic acidosis

2. Coexisting conditions:

   • Lactic acidosis can occur simultaneously with DKA, especially in critically ill patients
   • Lactic acid may contribute to metabolic acidosis in patients with true diabetic ketoacidosis 3

3. Treatment complications:

   • In some patients, ketoacidosis can be replaced by lactic acidosis during treatment 3
   • This transition is often associated with serious underlying disorders and poor prognosis

Clinical Scenarios Where Lactic Acid Testing is Particularly Important

• Patients with severe DKA (pH <7.00) 2
• Cases with disproportionate anion gap compared to ketone levels
• Patients with risk factors for lactic acidosis:
  • Shock or hypoperfusion states
  • Liver disease
  • Metformin use
  • Severe infection/sepsis
  • Hypoxemia

Diagnostic Framework for DKA

The American Diabetes Association defines DKA by the following criteria 1, 2:

• Blood glucose >250 mg/dL (though euglycemic DKA can occur)
• Arterial pH <7.3
• Serum bicarbonate <15 mEq/L
• Moderate ketonemia or ketonuria

When evaluating a patient with suspected DKA, the following laboratory tests should be obtained:

• Electrolytes, BUN, creatinine
• Venous or arterial pH
• Serum ketones (preferred) or urine ketones
• Blood glucose
• Lactic acid to evaluate for concurrent lactic acidosis 1
• Complete blood count
• Urinalysis

Clinical Pitfalls to Avoid

1. Missing euglycemic DKA:

   • Patients can present with normal blood glucose levels (<200 mg/dL) but still have DKA 4, 5
   • SGLT2 inhibitors increase risk of euglycemic DKA 2, 4
   • Lactic acid testing helps evaluate the cause of acidosis in these cases

2. Attributing all acidosis to ketones:

   • Failure to measure lactate may lead to overlooking mixed acid-base disorders
   • Up to 25% of DKA patients have emesis, which may worsen acidosis 1

3. Overlooking treatment-related lactic acidosis:

   • Transient increases in blood lactate can occur during DKA treatment 3
   • Monitoring lactate helps distinguish persistent DKA from treatment-related lactic acidosis

Conclusion

Checking lactic acid levels is a reasonable and important component of the laboratory evaluation when assessing diabetic patients for DKA. It helps identify mixed acid-base disorders, guides appropriate management, and assists in determining the true cause of metabolic acidosis, especially in complex cases or when the clinical picture doesn't align with laboratory findings.