Laboratory Monitoring for Pediatric Starvation Ketosis
For pediatric patients with starvation ketosis due to vomiting and poor oral intake, blood β-hydroxybutyrate (bOHB) measurement is the preferred monitoring method, with testing every 2-4 hours during acute management until clinical improvement occurs. 1
Initial Laboratory Assessment
- Obtain blood glucose, venous blood gases, electrolytes (with calculated anion gap), blood urea nitrogen, creatinine, and serum ketones (specifically β-hydroxybutyrate) as the initial laboratory panel 2
- Measure venous pH and serum bicarbonate to differentiate starvation ketosis from diabetic ketoacidosis (DKA) 2
- Calculate the anion gap to assess the severity of the metabolic derangement 1
- Assess hydration status through blood urea nitrogen/creatinine ratio and electrolyte concentrations 2
Differential Diagnosis: Starvation Ketosis vs. DKA
- Starvation ketosis typically presents with mildly elevated glucose (rarely >250 mg/dl) or even hypoglycemia, unlike DKA 2
- Serum bicarbonate in starvation ketosis is usually not lower than 18 mEq/L, whereas DKA shows bicarbonate <15 mEq/L 2
- β-hydroxybutyrate is elevated in both conditions, but typically lower in starvation ketosis than in DKA 1
- Anion gap may be elevated but is typically less pronounced in starvation ketosis compared to DKA 2
Recommended Laboratory Monitoring Schedule
- During acute management: Check blood glucose, electrolytes, venous pH, and β-hydroxybutyrate every 2-4 hours until clinical improvement 2, 1
- After initial stabilization: Monitor electrolytes and β-hydroxybutyrate every 4-6 hours until resolution 2
- For ongoing monitoring after improvement: Daily β-hydroxybutyrate until normalized and adequate oral intake is established 1
Specific β-hydroxybutyrate Monitoring
- Blood β-hydroxybutyrate is the preferred method for monitoring ketosis as it is the predominant ketone body in starvation states 2, 1
- Direct measurement of β-hydroxybutyrate is superior to urine ketone testing, which only measures acetoacetate and acetone 2, 1
- Target β-hydroxybutyrate levels <1.0 mmol/L indicate resolution of ketosis 3
- If blood β-hydroxybutyrate testing is unavailable, urine ketones can be used as an alternative but are less reliable 2
Monitoring Fluid and Electrolyte Status
- Check serum sodium, potassium, chloride, and bicarbonate with each blood draw 2
- Monitor for development of hypoglycemia, which can occur during rehydration 2
- Assess hydration status clinically and through laboratory parameters (BUN/creatinine ratio) 2
- Calculate corrected sodium for any hyperglycemia present (add 1.6 mEq to sodium value for each 100 mg/dL glucose >100 mg/dL) 2
Resolution Criteria
- Blood glucose within normal range for age 2
- Venous pH >7.3 1
- Serum bicarbonate ≥18 mEq/L 1
- Blood β-hydroxybutyrate <1.0 mmol/L 3
- Anion gap normalized (≤12 mEq/L) 1
- Adequate oral intake established 2
Important Considerations
- Starvation ketosis can be exacerbated by concurrent illness, especially with vomiting and poor oral intake 2
- In pediatric patients, monitoring should be more frequent than in adults due to their higher risk of rapid decompensation 4
- Avoid overaggressive fluid replacement, which can lead to cerebral edema, especially in younger children 4
- Consider monitoring for hypoglycemia, which can occur during rehydration therapy 2
Pitfalls to Avoid
- Do not rely solely on urine ketone testing, as it may underestimate total ketone body concentration by missing β-hydroxybutyrate 2, 1
- Avoid misdiagnosing starvation ketosis as DKA, which would lead to unnecessary insulin administration 2
- Remember that nitroprusside-based ketone tests (urine dipsticks) do not measure β-hydroxybutyrate and may provide misleading clinical information 2
- Be aware that during recovery, β-hydroxybutyrate converts to acetoacetate, which may make urine ketones appear to worsen while the patient is actually improving 2