Can vomiting lead to metabolic acidosis?

Vomiting and Metabolic Acidosis: Pathophysiology and Clinical Implications

Vomiting can lead to metabolic acidosis through several mechanisms, particularly when prolonged or severe, despite the common association of vomiting with metabolic alkalosis. 1

Mechanisms of Vomiting-Induced Metabolic Acidosis

Primary Mechanisms

1. Starvation Ketoacidosis

   • Prolonged vomiting leads to decreased food intake and fasting state
   • Triggers lipolysis and ketone body production (β-hydroxybutyrate, acetoacetate)
   • Results in high anion gap metabolic acidosis 2

2. Volume Depletion and Renal Effects

   • Severe dehydration from persistent vomiting
   • Reduced renal perfusion and glomerular filtration
   • Impaired acid excretion by kidneys 1

3. Paradoxical Acidosis

   • Despite loss of gastric acid (which typically causes alkalosis)
   • Occurs when other acidosis-inducing factors overwhelm the alkalinizing effect 3, 4

Special Populations at Risk

• Infants and Young Children

  • Higher body surface-to-weight ratio
  • Higher metabolic rate
  • Dependence on others for fluid intake 1
  • More susceptible to rapid dehydration and metabolic derangements

• Patients with Underlying Conditions

  • Neuromuscular disorders (e.g., spinal muscular atrophy)
  • Metabolic disorders
  • Food protein-induced enterocolitis syndrome (FPIES) 1, 5

Clinical Presentation

Signs and Symptoms

• Repetitive vomiting
• Lethargy and altered mental status
• Dehydration (dry mucous membranes, decreased skin turgor)
• Tachypnea (compensatory respiratory response to acidosis)
• Hypotension in severe cases 1

Laboratory Findings

• Decreased serum pH and bicarbonate
• Elevated anion gap (in ketoacidosis)
• Possible normal anion gap in certain conditions 6
• Electrolyte abnormalities (may include hyponatremia, hypokalemia)
• Elevated ketones in blood and/or urine 4
• Possible leukocytosis with left shift in inflammatory conditions 1, 5

Differential Diagnosis of Vomiting with Acidosis

1. Starvation Ketoacidosis

   • Prolonged vomiting leading to fasting state
   • Positive urine ketones, elevated β-hydroxybutyrate 2

2. Food Protein-Induced Enterocolitis Syndrome (FPIES)

   • Non-IgE-mediated food allergy
   • Repetitive vomiting 1-4 hours after food ingestion
   • Can lead to dehydration and metabolic acidosis 1, 5, 7

3. Organic Acidemias

   • Metabolic disorders with toxic encephalopathy
   • Vomiting, poor feeding, neurologic symptoms
   • Recurrent ketoacidosis 1

4. Adrenal Insufficiency

   • Vomiting with hyponatremia
   • May present with hypotension
   • Metabolic acidosis in severe cases 1

Management Approach

Immediate Interventions

1. Fluid Resuscitation

   • Intravenous crystalloid fluids
   • Correct volume depletion
   • Include glucose in solution to suppress ketogenesis 4

2. Electrolyte Correction

   • Replace deficits based on laboratory values
   • Monitor potassium, sodium, chloride levels

3. Bicarbonate Therapy

   • Consider in severe acidosis (pH < 7.1)
   • Use cautiously and monitor response 4

Addressing Underlying Cause

1. For FPIES or Food Allergies

   • Identify and eliminate trigger foods
   • Consider extensively hydrolyzed formula in infants 7

2. For Mechanical Obstruction

   • Surgical intervention if indicated (e.g., pyloric stenosis, band slippage) 2, 6

3. For Metabolic Disorders

   • Specialized management with metabolic team
   • May require specific dietary interventions 1

Prevention and Follow-up

• Identify patients at high risk for metabolic derangements
• Early intervention for persistent vomiting
• Close monitoring of fluid status and electrolytes
• Education regarding warning signs requiring medical attention

Special Considerations

• Patients with neuromuscular disorders may be particularly susceptible to ketoacidosis even after mild vomiting episodes 4
• Children with metabolic disorders require careful planning for procedures requiring fasting 1
• Patients with chronic conditions may need individualized emergency protocols

Vomiting-induced metabolic acidosis represents an important clinical entity that requires prompt recognition and management to prevent serious complications including severe dehydration, electrolyte imbalances, and potential cardiovascular compromise.