JW, Matzke GR. Acid–Base Disorders. In: DiPiro, JT, Talbert
RL, Yee GC, Matzke GR, Wells BG, Posey LM. Pharmacotherapy: A Pathophysiologic
Approach. 8th ed. http://accesspharmacy.com/content.aspx?aid=7984321.
Accessed August 7, 2012.
- Acid–base disorder characterized by decreased
pH and serum bicarbonate (HCO3–) concentrations.
- Decreased HCO3– results from many clinical situations
1. Common Causes of Metabolic Acidosis ||Download (.pdf)
1. Common Causes of Metabolic Acidosis
Increased Serum Anion Gap
Normal Serum Anion Gap/Hyperchloremic
GI bicarbonate loss
Renal failure (acute or chronic)
External pancreatic or small bowel drainage (fistula)
Ethylene glycol ingestion
Cholestyramine (bile acid diarrhea)
Magnesium sulfate (diarrhea)
Calcium chloride (acidifying agent)
Renal tubular acidosis
Proximal renal tubular acidosis (type II)
Distal renal tubular acidosis (type I)
Carbonic anhydrase inhibitors (e.g., acetazolamide)
Generalized distal nephron dysfunction (type IV)
Mineralocorticoid deficiency or resistance
Potassium-sparing diuretics (amiloride, spironolactone,
Angiotensin-converting enzyme inhibitors and receptor blockers
Nonsteroidal antiinflammatory drugs
Acid ingestion (ammonium chloride, hydrochloric acid, hyperalimentation)
Expansion acidosis (rapid saline administration)
- Metabolic acid–base disorders caused by changes in (HCO3–).
- Metabolic acidosis characterized by decreased pH and serum HCO3– concentrations resulting from:
- Addition of organic acid to extracellular fluid (e.g., lactic acid and ketoacids)
- Loss of HCO3– stores (e.g., diarrhea)
- Accumulation of endogenous acids due to impaired renal function (e.g., phosphates and sulfates).
- Serum anion gap (SAG) can be used to elucidate cause of metabolic
acidosis (Table 1), calculated as
- SAG = [Na+] – [Cl–] – [HCO3–]
- Normal anion gap is ~9 mEq/L (9 mmol/L),
with range of 3–11 mEq/L (3–11 mmol/L).
- SAG relative rather than absolute indication of cause of metabolic acidosis.
- Primary compensatory mechanism: decrease Paco2 by
increasing respiratory rate.
- Common chronic diseases and use of medications (Table 1)
- Relatively asymptomatic if acidosis acute and mild.
- Cardiovascular, respiratory, and central nervous systems
can be affected with severe metabolic acidemia (pH <7.15–7.2).
- Loss of appetite
- Rapid heartbeat
- Wide pulse pressure
- Cerebral: obtundation or coma
- Hyperventilation with deep, rapid respirations with severe
- Chronic acidemia: bone demineralization with development of
rickets in children and osteomalacia and osteopenia in adults.
Means of Confirmation and Diagnosis
- Primary tools for determining cause of acid–base
disorders and designing therapy:
- Blood gases (Table 2)
- Serum electrolytes...