Management of Metabolic Acidosis in a 3-Year-Old with Nausea, Vomiting, and Impaired Renal Function
This child requires immediate IV fluid resuscitation with 5% dextrose solution to correct metabolic acidosis and prevent further kidney injury, while addressing the underlying cause of persistent vomiting.
Initial Assessment and Stabilization
Laboratory Interpretation
- CO2 of 17 mmol/L indicates metabolic acidosis
- BUN of 24 mg/dL suggests pre-renal azotemia/dehydration
- Bilirubin of 1.4 mg/dL may indicate mild liver dysfunction or hemolysis
- These findings, combined with 4-day history of vomiting, point to dehydration with metabolic acidosis and impaired renal function
Immediate Management
IV Fluid Resuscitation
Electrolyte Correction
- Monitor serum electrolytes (Na, K, Cl, HCO3) every 4-6 hours
- Add potassium supplementation once urine output is established
- Consider bicarbonate therapy only if pH < 7.2 or bicarbonate < 18 mmol/L 2
Antiemetic Therapy
- Ondansetron 0.1 mg/kg IV (for a child weighing ≤40 kg) 3
- Administer over at least 30 seconds
Diagnostic Workup
Essential Laboratory Tests
- Complete blood count
- Comprehensive metabolic panel (already started)
- Urinalysis (specific gravity, pH, ketones)
- Urine electrolytes and osmolality
- Blood gas analysis to determine severity of acidosis
- Calculate anion gap: [Na+] - ([HCO3-] + [Cl-]) 4
Imaging
- Renal ultrasound to assess kidney size and structure
- Consider abdominal ultrasound to evaluate for pyloric stenosis or other obstructive pathology
Differential Diagnosis and Specific Management
1. Renal Tubular Acidosis (RTA)
- Consider if anion gap is normal with persistent acidosis
- Evaluate urine pH and fractional excretion of bicarbonate
- Management:
- Bicarbonate supplementation if chronic
- Potassium supplementation if hypokalemic
2. Bartter Syndrome
- Consider if hypochloremic, hypokalemic metabolic alkalosis develops after rehydration
- Check urinary calcium excretion and renin/aldosterone levels
- Management:
- NSAIDs (indomethacin 1-4 mg/kg/day divided in 3-4 doses) 1
- Potassium supplementation
- Salt supplementation
3. Diabetic Ketoacidosis
- Check blood glucose and urine/serum ketones
- Management:
- Insulin therapy if confirmed
- Careful fluid management
4. Pyloric Stenosis or Gastric Outlet Obstruction
- Consider if persistent vomiting without diarrhea
- Typically presents with metabolic alkalosis, but can present with paradoxical acidosis 5
- Management:
- Surgical consultation if confirmed
Monitoring and Follow-up
Short-term Monitoring
- Vital signs including blood pressure every 1-2 hours initially
- Strict input and output monitoring
- Daily weight measurements
- Repeat electrolytes every 4-6 hours until stable
Long-term Follow-up
- For children with persistent renal issues, follow-up every 3-6 months 1
- Monitor:
- Growth and development
- Serum electrolytes
- Renal function
- Acid-base status
Special Considerations
Pitfalls to Avoid
- Don't use normal saline for fluid resuscitation - can worsen acidosis and increase renal solute load 1
- Don't administer bicarbonate routinely - focus on treating underlying cause and use bicarbonate only for severe acidosis (pH < 7.2) 2
- Don't forget to monitor potassium - both hypokalemia and hyperkalemia can occur during treatment
- Don't overlook the possibility of paradoxical acidosis - children with neuromuscular disorders or severe malnutrition can develop metabolic acidosis after vomiting instead of the expected alkalosis 6
Nutritional Support
- Once vomiting subsides, begin oral rehydration with appropriate electrolyte solutions
- Progress to age-appropriate diet with adequate calories (130 kcal/kg/day) and protein (4 g/kg/day) 1
- Consider enteral tube feeding if oral intake remains poor