What is the treatment for a 2-year-old with vomiting and high anion gap metabolic acidosis?

Treatment of a 2-Year-Old with Vomiting and High Anion Gap Metabolic Acidosis

Immediately initiate fluid resuscitation with 20 mL/kg boluses of 0.9% normal saline or 4.5% albumin, obtain comprehensive laboratory testing to identify the underlying cause (glucose, lactate, ketones, toxicology screen), and treat the specific etiology while avoiding routine bicarbonate therapy unless pH is critically low or specific indications exist. 1, 2

Immediate Resuscitation and Stabilization

Fluid Management

• Administer 20 mL/kg boluses of isotonic saline (0.9% NaCl) or 4.5% albumin solution immediately to restore intravascular volume and tissue perfusion 1, 2
• Repeat fluid boluses up to 40 mL/kg total if shock persists, monitoring clinical response closely 1
• For children in coma with shock, 4.5% albumin may be preferred over crystalloid 1
• If shock persists despite 40 mL/kg fluid resuscitation, consider central venous pressure monitoring to guide further management 1

Essential Laboratory Testing

Obtain immediately: 2

• Plasma glucose (to identify diabetic ketoacidosis)
• Serum lactate (lactic acidosis carries high mortality)
• Serum and urine ketones
• Complete metabolic panel with calculated anion gap
• Arterial or venous blood gas
• BUN/creatinine (uremic acidosis)
• Toxicology screen including salicylate, methanol, ethylene glycol levels
• Complete blood count
• Serum osmolality

Differential Diagnosis Based on Anion Gap 21

Most Likely Causes in a 2-Year-Old with Vomiting

Diabetic Ketoacidosis (if glucose >250 mg/dL): 3, 2

• Characterized by glucose >250 mg/dL, pH <7.3, bicarbonate <15 mEq/L, positive ketones
• Initiate insulin therapy immediately (0.1 U/kg/hr IV infusion after initial bolus)
• Continue fluid resuscitation at 1.5 times maintenance requirements (approximately 5 mL/kg/hr)
• Add dextrose (D10%) to IV fluids when glucose reaches 250 mg/dL 3

Lactic Acidosis (most common in pediatric shock/sepsis): 2, 4

• Elevated lactate typically >4 mmol/L
• Associated with hypoxia, sepsis, tissue hypoperfusion, or mesenteric ischemia
• Treatment focuses on addressing underlying cause (oxygen delivery, treating sepsis, restoring perfusion)
• Administer broad-spectrum antibiotics immediately if infection suspected 2

Toxic Ingestion (salicylates, methanol, ethylene glycol): 2, 4

• Check toxicology screen and osmolar gap
• Specific antidotes required based on toxin identified

Inborn Errors of Metabolism (less common but important in this age group): 5

• Consider if no obvious cause identified
• May present with vomiting, failure to thrive, and severe acidosis

Bicarbonate Therapy: When and How

Generally NOT Recommended

• Avoid routine bicarbonate use in DKA - has not been shown to improve resolution of acidosis or time to discharge 1
• Avoid routine bicarbonate in lactic acidosis - may worsen intracellular acidosis without improving outcomes 1
• Bicarbonate generates CO2, which can worsen outcome in many cases 4

Specific Indications for Bicarbonate

Consider bicarbonate only if: 6

• Severe acidosis with life-threatening hemodynamic instability
• pH critically low with cardiovascular compromise
• Specific toxins (salicylates, tricyclic antidepressants)

Dosing if indicated: 6

• Initial dose: 1-2 mEq/kg IV over 4-8 hours
• Monitor arterial blood gases, electrolytes (especially potassium), and clinical response
• Aim for bicarbonate ~18-20 mEq/L initially, not full correction in first 24 hours
• Rapid correction risks overshoot alkalosis due to delayed ventilatory adjustment

Monitoring During Treatment

Assess every 1-2 hours initially: 2

• Arterial or venous blood gas (venous pH typically 0.03 lower than arterial)
• Electrolytes with calculated anion gap
• Glucose and lactate levels
• Clinical perfusion status (capillary refill, mental status, urine output >1 mL/kg/hr)

Critical electrolyte management: 1

• Monitor potassium closely - acidosis correction can cause life-threatening hypokalemia
• Correct hyperkalemia immediately if present, especially if bowel infarction suspected

Treatment Goals

Target endpoints: 3

• Normal perfusion with capillary refill ≤2 seconds
• Urine output >1 mL/kg/hr
• Normal mental status
• Resolution of anion gap and lactate elevation
• Bicarbonate >18 mEq/L (not necessarily normal in first 24 hours)

Common Pitfalls

• Do not attempt full correction of acidosis in first 24 hours - risks overshoot alkalosis with delayed ventilatory compensation 6
• Do not use bicarbonate reflexively - identify and treat underlying cause first 1
• Do not overlook toxic ingestions - always obtain toxicology screen in unexplained high anion gap acidosis 2
• Do not forget to correct sodium for hyperglycemia - add 1.6 mEq for each 100 mg/dL glucose >100 mg/dL 3, 2
• In vomiting with severe acidosis, consider cow milk protein allergy - can cause severe dehydration and high anion gap acidosis in infants 7