Management of Ketones in Urinalysis for Children with Suspected DKA
The management of a child with ketones in their urine who is suspected of having diabetic ketoacidosis (DKA) requires immediate assessment and treatment with intravenous fluids, insulin therapy, and close monitoring of blood glucose and ketone levels to prevent morbidity and mortality.
Initial Assessment and Diagnosis
Diagnostic criteria for DKA 1:
- Blood glucose >250 mg/dL
- Venous pH <7.3
- Bicarbonate <15 mEq/L
- Moderate ketonuria or ketonemia
Key laboratory tests 1:
- Blood glucose
- Venous blood gases
- Electrolytes (particularly potassium)
- Blood urea nitrogen (BUN)
- Creatinine
- Calcium and phosphorous
- Urinalysis
Ketone measurement considerations 1, 2:
- Blood β-hydroxybutyrate (βOHB) measurement is preferred over urine ketones for diagnosis and monitoring
- Urine ketones are highly sensitive for DKA with high negative predictive value
- Urine tests primarily detect acetoacetate using nitroprusside reaction but miss βOHB (the predominant ketone in DKA)
Treatment Algorithm
1. Fluid Resuscitation
- Initial fluid therapy 1:
- For pediatric patients: 1.5 times the 24-hour maintenance requirement (approximately 5 mL/kg/hr)
- Do not exceed twice the maintenance requirement to avoid cerebral edema
- The potassium in solution should be 1/3 KPO₄ and 2/3 KCl or K-acetate (once urine output is established and K <5.5 mEq/L)
2. Insulin Therapy
For moderate to severe DKA 1:
- Avoid initial insulin bolus in pediatric patients
- When plasma glucose reaches 250 mg/dL, start continuous insulin infusion at 0.1 unit/kg/hr
- This typically decreases plasma glucose at 50-75 mg/dL/hr
For mild DKA 1:
- "Priming" dose of regular insulin (0.4-0.6 units/kg)
- Half as IV bolus and half as subcutaneous/intramuscular injection
- Follow with 0.1 unit/kg/hr subcutaneously or intramuscularly
3. Monitoring and Adjustment
Glucose monitoring 1:
- If plasma glucose doesn't fall by 50 mg/dL in first hour, check hydration status
- If hydration is acceptable, double insulin infusion hourly until steady glucose decline of 50-75 mg/hr is achieved
- When glucose reaches 200 mg/dL, add 5-10% dextrose to IV fluids while continuing insulin
Ketone monitoring 1:
- Blood βOHB measurement is the preferred method for monitoring DKA
- Do not use nitroprusside method (urine ketones) to monitor treatment response
- During therapy, βOHB converts to acetoacetate, which may falsely suggest worsening ketosis when using nitroprusside method
Electrolyte monitoring 1:
- Check electrolytes, glucose, BUN, creatinine, osmolality, and venous pH every 2-4 hours
- Monitor potassium closely and maintain between 4-5 mEq/L
4. Resolution Criteria and Transition
DKA resolution criteria 1:
- Glucose <200 mg/dL
- Serum bicarbonate ≥18 mEq/L
- Venous pH ≥7.3
- Anion gap <12 mEq/L
Transition to subcutaneous insulin 1:
- Once DKA is resolved and patient can eat, transition to multiple-dose insulin regimen
- Continue IV insulin for 1-2 hours after starting subcutaneous insulin to ensure adequate plasma insulin levels
Special Considerations and Pitfalls
Cerebral edema prevention 1, 3:
- Most serious complication of DKA treatment in children
- Avoid excessive or too-rapid fluid administration
- Monitor neurological status closely
Potassium management 1:
- Despite total-body potassium depletion, mild to moderate hyperkalemia is common initially
- Begin potassium replacement when levels fall below 5.5 mEq/L (assuming adequate urine output)
- If significant hypokalemia is present at diagnosis, delay insulin until potassium is restored to >3.3 mEq/L
- Relying solely on urine ketones to monitor treatment response
- Abrupt discontinuation of IV insulin before subcutaneous insulin takes effect
- Failure to recognize that ketonemia takes longer to clear than hyperglycemia
By following this structured approach to the management of ketones in children with suspected DKA, clinicians can effectively treat this medical emergency while minimizing the risk of complications.