Metabolic acidosis

Formula

• PCO2 = (1.5 x [HCO3–] + 8) ± 2
• In acute setting PCO2 falls by 1 mmHg for every 1 mEq fall in HCO3

DDX

Gap

1. Lactic acidosis
2. Renal failure
3. Ketoacidosis
   1. DM
   2. ETOH
   3. Starvation
   4. High fat diet
4. Tox ingestion
   1. Inc osm gap
      1. Methanol
      2. Ethylene glycol
   2. Nl osm gap
      1. Salicylate
      2. Paraldehyde
      3. Cyanide

Non-gap

1. Hyperkalemia
   1. Resolving DKA
   2. Early uremic acidosis
   3. Early obstructive
   4. RTA Type IV
   5. Hypoaldo
   6. K-sparing diuretics
2. Hypokalemia
   1. RTA Type I
   2. RTA Type II
   3. Acetazolamide
   4. Acute diarrhea
      1. (May be assoc with gap if hypoperfusion -> lactic acidosis)

Treatment

Treat source

Bicarbonate Indications

1. Bicarb <4
2. pH <7.10 + Sx shock/myocardial irritability
3. Severe hyperchloremic acidemia + Sx shock/myocardial irritability

Source

2/21/06 DONALDSON (adapted from Tintinalli)