EMPIRIC ABG EQUATIONS ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ The basic (most important) equations for analyzing compensation for acid-base disorder should be memorized: ÉÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ» º For metabolic alkalosis or acidosis, with respiratory compensation: º º pCO2 = last 2 digits of the pH = [HCO3-] + 15 º º (for [HCO3-] from 8 to 35) º ÌÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ͹ º For respiratory acidosis, every increase in pCO2 has an expected º º decrease in pH: º º pCO2 10 = pH .08 (acute) º º pCO2 10 = pH .03 (later, with metabolic compensation) º ÌÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ͹ º For respiratory alkalosis, each decrease in pCO2 has an expected º º decrease in bicarbonate: º º pCO2 10 = [HCO3] 2 (acute) º º pCO2 10 = [HCO3] 5 (chronic/compensated) º ÈÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍͼ Many other empiric equations are available to those who enjoy memorizing equations.