What is a direct cause of metabolic acidosis?

Causes of Metabolic Acidosis

Uncontrolled diabetes (option A) is a direct cause of metabolic acidosis due to the development of diabetic ketoacidosis (DKA). 1, 2

Pathophysiology of Metabolic Acidosis in Different Conditions

Uncontrolled Diabetes (Correct Answer)

• In uncontrolled diabetes, insulin deficiency combined with elevated counterregulatory hormones (glucagon, catecholamines, cortisol, growth hormone) leads to: 1
  • Increased lipolysis (release of free fatty acids from adipose tissue)
  • Unrestrained hepatic fatty acid oxidation producing ketone bodies (β-hydroxybutyrate and acetoacetate)
  • Resulting ketonemia and metabolic acidosis
• This process creates diabetic ketoacidosis (DKA), a serious acute metabolic complication with 5% mortality even when properly managed 1

Incorrect Options Analysis:

B. Forced Hyperventilation

• Causes respiratory alkalosis (not acidosis) through excessive elimination of CO₂
• Hyperventilation is actually a compensatory mechanism for metabolic acidosis, not a cause 2
• The respiratory system responds to metabolic acidosis by increasing ventilation to eliminate excess CO₂ and raise blood pH

C. Loss of Gastric Acids

• Causes metabolic alkalosis (not acidosis) due to loss of hydrogen ions
• Vomiting removes acidic gastric contents, leading to relative alkalinity in the blood

D. Ingestion of Sodium Bicarbonate

• Causes metabolic alkalosis (not acidosis) as bicarbonate is a base
• Sodium bicarbonate is actually used therapeutically to treat metabolic acidosis when serum bicarbonate falls below 22 mmol/L 2

E. Emphysema

• Can cause respiratory acidosis (not metabolic acidosis) due to CO₂ retention
• Emphysema impairs gas exchange and can lead to CO₂ accumulation, but this is a respiratory, not metabolic, acid-base disturbance

Clinical Presentation of Metabolic Acidosis in Uncontrolled Diabetes

• Symptoms develop relatively quickly (typically within 24 hours) 1
• Classic presentation includes:
  • Polyuria, polydipsia, polyphagia
  • Weight loss, vomiting, abdominal pain
  • Dehydration, weakness
  • Kussmaul respirations (deep, rapid breathing - compensatory mechanism)
  • Altered mental status potentially progressing to coma 1

Laboratory Findings in Diabetic Ketoacidosis

• Decreased pH (<7.35)
• Decreased serum bicarbonate
• Elevated anion gap due to presence of ketone bodies (β-hydroxybutyrate, acetoacetate) 3
• Hyperglycemia
• Ketonemia and ketonuria

Treatment Approach for DKA

• IV insulin infusion (0.1 units/kg/hr)
• Electrolyte replacement (particularly potassium)
• Close monitoring of glucose levels 2
• Hydration with balanced crystalloid solutions
• Treatment should focus on correcting the underlying cause rather than just the acidosis 4