Arterial blood gases

Approach to Arterial Blood Gases

Classify the acid-base disturbance based on pH.

Increased anion gap in metabolic acidosis; decreased in hypoalbuminemia, paraproteinemia, halide ingestion, lab error)

anion gap = Na⁺ = Cl^- - HCO₃ ; normal is <8-12

Δ in HCO₃ should equal the Δ in anion gap

Δ in HCO₃ should equal Δ in PCO₂ x correction factor of xxx

If PCO₂ is not available, can calculate by

If over 10% error, then one of the values is wrong

pH = -log[H+]

ie pH 7.4 = 10^-7.4 mol/L H+ = 40

For a pH range of 7.25-7.55

drop the 7.

subtract from 80

ie pH 7.38 = 42

x 0.8 for every increase of 0.1 in pH

/ 0.8 for every decrease of 0.1 in pH

pH 7.00 = 100 nM H+

ph 7.4 = 40 nM H+

arterial blood gas sampling (Dalhousie University Common Common Currency)