Acidosis occurs in the main due to increased formation of acid or lack of
elimination of formed acid or both. Increased formation of acid is mainly
seen in the context of poor tissue perfusion with a switch to anaerobic
metabolism and the formation of lactic acid. Decreased elimination of acid is
mainly a feature of renal failure. Respiratory acidosis in the context of
hypoventilation is caused by the lack of elimination of carbon dioxide with
increased formation of HCO
.
Accumulation of lactic acid will cause lactic acidosis. The anion gap, see
equation 1 is increased. To compensate the body will use its
buffer systems to reduce the change in pH
, more carbon dioxide will be formed
due to the HCO
buffer system, see equation 4.
The proton concentration in the cerebrospinal fluid will rise and the
respiratory centre will be stimulated to increase the frequency and depth of
respiration. Consequent to the increased minute ventilation the paCO2
will
fall.
| Normal anion gap | |
| Bicarbonate loss | Diarrhoea
Bile/pancreatic fluid loss Ureterosigmoidostomy Long or obstructed ileal conduit Carbonic anhydrase inhibitors |
| Renal tubular dysfunction | Renal tubular acidosis
Tubulointestinal disease |
| Acid loading | Ammonium chloride
Parenteral feeding (Arginine and Lysine HCl) |
| Increased anion gap | |
| Overproduction of acid | Lactic acidosis
Ketoacidosis (diabetic, alcohol, starvation) Salicyclate Methanol Ethylene glycol Paraldehyde |
| Renal failure | Acute or Chronic |