Bicarbonate concentration have been
used to estimate pH and pCO2.
E.g. if HCO3-
= 10 mmol/L
Then for pH determination,
10 + 15 = 25, Thus pH = 7.25
For estimating pCO2 (mm
Hg), following formula is used:
pCO2 ± 2 = 1.5 (cHCO3-) + 8
1.5 (10) + 8 or 23 ± 2 is pCO2.
Electrolytes are also altered
depending upon the cause of metabolic acidosis. Eg. in diabetic ketoacidosis (DKA),
the increase in organic acids caused by increased ketone bodies is reflected by
decrease in plasma bicarbonate and sometimes chloride. Plasma sodium and
potassium are also decreased due to polyuria and coexcretion with acetoacetate
and beta hydroxy butyrate. Fruthermore, because of high glucose, there is
dilutional effect as a result of osmotically induced increase in vascular
volume. When glucose concentration decreases following insulin treatment, water
leaves the vascular compartment and sodium concentration increases.
Chronic metabolic acidosis enhances
mobilization of calcium from bones; the decrease in plasma pH increases
dissociation of plasma proteins bound calcium so that more calcium is filtered
through the glomerulus and less is reabsorbed.
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