Can a patient with type 1 diabetes and elevated beta hydroxybutyrate (BHB) be in diabetic ketoacidosis (DKA) with a normal Venous Blood Gas (VBG) pH and slightly elevated anion gap (AG)?

Beta Hydroxybutyrate Elevation with Normal pH in Type 1 Diabetes

Yes, a patient with type 1 diabetes can have an elevated beta hydroxybutyrate (BHB) of 3.83 mmol/L and be in diabetic ketoacidosis (DKA) despite having a normal venous pH of 7.41 and slightly elevated anion gap of 21. 1, 2

Diagnosis of DKA with Atypical Presentation

Key Diagnostic Considerations

• According to the American Diabetes Association guidelines, the diagnosis of DKA requires:

  1. Hyperglycemia
  2. Elevated blood ketone bodies (specifically BHB)
  3. Acidosis with increased anion gap 3

• However, atypical presentations exist:

  • BHB levels ≥3.0 mmol/L in children and ≥3.8 mmol/L in adults are diagnostic thresholds for DKA when uncontrolled diabetes is present, even when other parameters are atypical 4
  • The patient's BHB of 3.83 mmol/L meets the adult diagnostic threshold

Diabetic Ketoalkalosis: A Relevant Variant

• Diabetic ketoalkalosis (DKAlk) is characterized by:

  • Hyperglycemia (>250 mg/dL)
  • Elevated anion gap (>15 mEq/L)
  • Elevated BHB (>1.2 mmol/L)
  • Normal or elevated pH/bicarbonate 2

• This condition is more common than previously reported and often occurs in patients with vomiting and hypovolemia 2

Physiological Explanation

Mechanisms for Normal pH Despite Ketosis

1. Volume depletion and vomiting: Common in DKA patients, leading to metabolic alkalosis that can partially or completely offset the metabolic acidosis 2

2. Variable relationship between BHB and bicarbonate: The correlation between BHB and bicarbonate levels shows marked variability due to concurrent acid-base disturbances, especially hyperchloremic non-anion gap acidosis 4

3. Mixed acid-base disorders: DKA patients may have concurrent respiratory alkalosis (from hyperventilation) or metabolic alkalosis (from vomiting) 1

Clinical Implications

Management Considerations

• Despite normal pH, treatment should follow standard DKA protocols:

  • Fluid resuscitation with isotonic saline (15-20 ml/kg/hour initially)
  • Insulin therapy (0.1 U/kg/hour continuous IV infusion)
  • Electrolyte monitoring and replacement
  • Addressing underlying precipitating factors 1

• BHB monitoring is crucial:

  • Resolution of DKA is defined as BHB <1.5 mmol/L, along with traditional criteria (pH >7.3, bicarbonate ≥15 mEq/L, anion gap ≤14) 5
  • Specific BHB measurement should be used for diagnosis and monitoring rather than nitroprusside-based ketone tests 3

Common Pitfalls to Avoid

1. Relying solely on pH or bicarbonate: A normal pH does not exclude DKA, especially in mixed acid-base disorders 6

2. Using nitroprusside reaction tests: These do not measure BHB (the predominant ketone in DKA) and should not be used for diagnosis or monitoring 3

3. Depending only on venous blood gas electrolytes: VBG chloride may be falsely elevated, resulting in underestimation of anion gap and missed diagnosis of DKA 2

4. Overlooking BHB levels: BHB is the most reliable indicator of ketosis and should be measured directly 3, 5

Conclusion

The presence of significantly elevated BHB (3.83 mmol/L) in a type 1 diabetes patient is diagnostic of DKA despite normal pH and only moderately elevated anion gap. This represents an atypical presentation that requires standard DKA treatment while monitoring BHB levels to assess resolution.