Metabolic Acidosis

Increased anion gap metabolic acidosis

  • Anion Gap Metabolic acidosis  (gap > 10-12 mEq/L)
    • Signs/symptoms:  hyperventilation, N/V, hyperkalemia, hypotension, cardiac arrhythmias, lethargy, coma
    • Causes:  renal failure, ketoacidosis (diabetes, alcoholism, starvation), lactic acidosis (anemia, CO poisoning, shock), drug intoxication (methanol, ethylene glycol, salicylates, paraldehyde)
      • Methanol
      • Uremia
      • Diabetic ketoacidosis/starvation or EtOH ketoacidosis
      • Poisoning
      • Isoniazid/Intoxication/Infection
      • Lactic acidosis
      • Ethylene glycol/EtOH
      • Salicylates/Sepsis
    • Therapy:
      • Treat underlying cause (ex. diabetes for diabetic ketoacidosis, oxygen delivery for lactic acidosis)
      • IV sodium bicarbonate  (if pH < 7.10 or if hemodynamically compromised)
        • Determine bicarb deficit –> = (desired – current) x 0.5 x weight (kg)
          • Stop when bicarb = 7.2
      • Tromethamine
        • IV buffer alternative for patients with fluid overload (can’t handle any more Na)
        • Doesn’t generate excess CO2
        • IV: 1-5 mmol/kg/hr   (don’t admin for more than 24h)
        • Contraindicated in acute renal failure
      • Sub acetate or lactate salts for chloride salts in the TPNs
      • Dialysis
      • Oral therapy (usually for patients w/ chronic acidosis (renal failure))
        • Sodium bicarb tablets
        • Sodium citrate & citric acid (Shohl’s solution)
        • Potassium citrate/citric acid (Polycitra-K)

b.    Normal anion gap metabolic acidosis

  • Non-Anion Metabolic acidosis (gap < 10-12 mEq/L)
    • Ureteral diversion
    • Saline infusions
    • Exogenous acid
    • Diarrhea
    • Carbonic anhydrase inhibitors (acetazolamide)
    • Adrenal insufficiency
    • Renal tubular acidosis
  • Response:  pCO2 decreases [from a normal value of 40] by 1.0 – 1.4 mmHg for every 1 mEq drop in HCO3-
    • Can’t do this for an unlimited amount of time
  • Therapy:
    • Treat underlying cause (ex. diabetes for diabetic ketoacidosis, oxygen delivery for lactic acidosis)
    • IV sodium bicarbonate  (if pH < 7.10 or if hemodynamically compromised)
      • Determine bicarb deficit –> = (desired – current) x 0.5 x weight (kg)
        • Stop when bicarb = 7.2
    • Tromethamine
      • IV inert amino alcohol buffer alternative for patients with fluid overload (can’t handle any more Na)
      • Doesn’t generate excess CO2
      • IV: 1-5 mmol/kg/hr   (don’t admin for more than 24h)
      • Contraindicated in acute renal failure
    • Sub acetate or lactate salts for chloride salts in the TPNs
    • Dialysis
    • Oral therapy (usually for patients w/ chronic acidosis (renal failure))
      • Sodium bicarb tablets
      • Sodium citrate & citric acid (Shohl’s solution)
      • Potassium citrate/citric acid (Polycitra-K)

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