What is the role of blood ketones, specifically beta-hydroxybutyrate (BHB), in managing diabetic ketoacidosis (DKA)?

Role of Blood Ketones in Managing Diabetic Ketoacidosis (DKA)

Blood ketone measurement, specifically beta-hydroxybutyrate (BHB), is superior to urine ketone testing for both diagnosis and monitoring of DKA and should be the preferred method when available. 1

Diagnostic Value of Blood Ketones

• BHB is the predominant ketone body in DKA and provides the most accurate assessment of ketosis severity 1

• Diagnostic criteria for DKA include:

  • Blood glucose >250 mg/dL
  • Arterial pH <7.3
  • Bicarbonate <15 mEq/L
  • Moderate ketonemia or ketonuria 2

• Severity classification based on BHB levels:

  • Normal: <0.5 mmol/L
  • Elevated: >0.5 mmol/L (indicates need for intervention in at-risk patients)
  • DKA: Typically >3.0 mmol/L 1

Advantages of BHB Testing Over Urine Ketone Testing

1. More accurate reflection of ketosis: BHB is the strongest and most prevalent acid in DKA 1
2. Better correlation with clinical status: BHB correlates well with bicarbonate (r=-0.24139; P=0.0161) and pH (r=-0.56419; P<0.0001) 3
3. Earlier normalization: BHB normalizes earlier than ketonuria during treatment (15.5-37.3 hours vs. 18.8-41.7 hours, P<0.01) 3
4. Avoids false interpretation during treatment: Nitroprusside method only measures acetoacetic acid and acetone, not BHB 1

Monitoring DKA Treatment with BHB

• Recommendation: Specific measurement of BHB in blood should be used for diagnosis of DKA and for monitoring during treatment (Evidence level: B, moderate) 1

• Warning: Blood ketone determinations that rely on the nitroprusside reaction should NOT be used to monitor treatment of DKA (Evidence level: B, low) 1

• During DKA treatment, BHB converts to acetoacetic acid, which can make nitroprusside-based tests falsely suggest worsening ketosis 1

• Direct BHB measurement allows for more accurate assessment of treatment response and can guide insulin therapy adjustments 1

Clinical Applications and Benefits

• Reduced hospitalization time: Patients monitored with blood BHB left intensive care 6.5 ± 1.5 hours earlier than those monitored with urine ketones 4
• Cost savings: One study showed 2940 euros saved through reduced laboratory tests (29.8%) and clinical assessment time (70.2%) 4
• Earlier detection of ketosis: Allows for earlier intervention in at-risk patients (those with type 1 diabetes, history of DKA, or on SGLT2 inhibitors) 1
• Patient satisfaction: Greater satisfaction reported with blood ketone testing compared to urine testing 5

Practical Implementation

• For diagnosis: Use blood BHB measurement alongside glucose, pH, and bicarbonate levels
• For monitoring treatment:
  • Check BHB every 2-4 hours along with electrolytes, glucose, and venous pH 1
  • DKA resolution criteria: glucose <200 mg/dL, serum bicarbonate ≥18 mEq/L, venous pH >7.3, and normalized BHB levels (<0.5 mmol/L) 2

Patient Education and Home Monitoring

• Recommendation: Individuals prone to ketosis (type 1 diabetes, history of DKA, or on SGLT2 inhibitors) should measure ketones in urine or blood if they have unexplained hyperglycemia or symptoms of ketosis (Evidence level: B, moderate) 1
• Sick day management: Patients should check blood ketones during illness, implement sick day rules, and seek medical advice if ketone levels are elevated 1
• Blood ketone testing during illness has been shown to reduce emergency department visits and hospitalizations by almost 50% in children with type 1 diabetes 1

Common Pitfalls to Avoid

1. Relying on urine ketones during treatment: May falsely suggest worsening ketosis as BHB converts to acetoacetate
2. Using nitroprusside-based blood tests for monitoring: These don't measure BHB and can be misleading
3. Stopping treatment too early: About 10% of patients still have ketonuria when blood ketone levels have normalized 3
4. Overlooking BHB in euglycemic DKA: Particularly important in patients on SGLT2 inhibitors who may develop DKA without significant hyperglycemia 1