A. High-Anion Gap Metabolic Acidosis

• Lactic acidosis
• Ketoacidosis
  • Diabetic
  • Alcoholic
  • Starvation
• Toxins
  • Ethylene glycol
  • Methanol
  • Salicylates
  • Propylene glycol
  • Pyroglutamic acid (5-oxoproline)
• Renal failure (acute and chronic)

B. Normal-Anion Gap Metabolic Acidosis

1. Gastrointestinal bicarbonate loss
   1. Diarrhea
   2. Pancreatic/small-bowel drainage
   3. Ureterosigmoidostomy, jejunal/ileal loop
   4. Drugs
      1. Calcium chloride
      2. Magnesium sulfate
      3. Cholestyramine
2. Renal acidosis
   1. Hypokalemia
      1. Proximal RTA (type 2, drugs: acetazolamide, topiramate)
      2. Distal RTA (type 1, drugs: amphotericin B, ifosfamide)
   2. Hyperkalemia
      1. Type 4 RTA – Aldosterone deficiency/resistance, PHA, CKD
      2. Tubulointerstitial disease
   3. Normokalemia – CKD
3. Drug-induced hyperkalemia
   1. K-sparing diuretics
   2. Trimethoprim
   3. Pentamidine
   4. ACEIs, ARBs
   5. NSAIDs
   6. Calcineurin inhibitors
   7. Heparin
4. Other
   1. Acid loads (NH₄Cl, TPN)
   2. Loss of potential HCO₃⁻ (ketone excretion)
   3. Expansion acidosis (saline infusion)
   4. Hippurate

1. Exogenous HCO₃⁻ loads
   1. Acute alkali administration
   2. Milk-alkali syndrome
2. ECFV contraction + K⁺ deficiency
   1. GI origin
      1. Vomiting
      2. Gastric aspiration
      3. Congenital chloridorrhea
      4. Villous adenoma
   2. Renal origin
      1. Diuretics
      2. Posthypercapnia
      3. Hypercalcemia/hypoparathyroidism
      4. Recovery from acidosis
      5. Nonreabsorbable anions (penicillin, carbenicillin)
      6. Mg²⁺ deficiency
      7. K⁺ depletion
      8. Bartter’s syndrome
      9. Gitelman’s syndrome
3. ECFV expansion + mineralocorticoid excess
   1. High renin
      1. Renal artery stenosis
      2. Accelerated hypertension
      3. Renin-secreting tumor
      4. Estrogen therapy
   2. Low renin
      1. Primary aldosteronism
         1. Adenoma
         2. Hyperplasia
         3. Carcinoma
      2. Adrenal enzyme defects
         1. 11β-Hydroxylase deficiency
         2. 17α-Hydroxylase deficiency
      3. Cushing’s syndrome or disease
      4. Other
         1. Licorice
         2. Carbenoxolone
         3. Chewer’s tobacco
4. Liddle’s syndrome

1. Central
   1. Drugs (anesthetics, morphine, sedatives)
   2. Stroke
   3. Infection
2. Airway
   1. Obstruction
   2. Asthma
3. Parenchyma
   1. Emphysema
   2. Pneumoconiosis
   3. Bronchitis
   4. ARDS
   5. Barotrauma
4. Neuromuscular
   1. Poliomyelitis
   2. Kyphoscoliosis
   3. Myasthenia
   4. Muscular dystrophies
5. Miscellaneous
   1. Obesity
   2. Hypoventilation
   3. Permissive hypercapnia

1. CNS stimulation
   1. Pain
   2. Anxiety, psychosis
   3. Fever
   4. CVA
   5. Meningitis, encephalitis
   6. Tumor
   7. Trauma
2. Hypoxemia
   1. High altitude
   2. Pneumonia, pulmonary edema
   3. Aspiration
   4. Severe anemia
3. Drugs/Hormones
   1. Pregnancy (progesterone)
   2. Salicylates
   3. Cardiac failure
4. Chest receptor stimulation
   1. Hemothorax
   2. Flail chest
   3. Cardiac failure
   4. Pulmonary embolism
5. Miscellaneous
   1. Septicemia
   2. Hepatic failure
   3. Mechanical hyperventilation
   4. Heat exposure
   5. Recovery from metabolic acidosis