Brian Locke

Acid Base

Approach

  • Acidemia vs Alkalemia
  • Calculate anion gap: Na - (HCO+Cl)
  • Calculate the change in Anion Gap: AG - 12
  • Calculate the delta delta: Change in Anion Gap + HCO3 should equal 24. If < 22, concomitant NAGMA. If > 26, concomitant Met Alk
  • Assess if compensation is adequate.

##Compensation ###Metabolic Acidosis PCO2 = last 2 digits of pH PCO2 = 1.5*HCO3 + 8

###Metabolic Alkalosis PCO2 = 40 + .6 * (HCO3-24) aka the change in bicarbonate

###Respiratory Acidosis Acute: HCO3 = delta_PaCO2 / 10 OR pH change = 0.008 * CO2 change. (38 normal in SLC)

Chronic: HCO3 = (delta_PaCO2 / 10) * 3.5 or pH change = 0.003 * CO2 Change

###Respiratory Alkalosis Acute: HCO3 = delta PaCO2 / 10

Chronic: HCO3 = (delta_PaCO2 / 10) * 3.5

Stewart Approach

Strong ion approach -https://journals.lww.com/ccmjournal/Abstract/2007/11000/Disorders_of_acid_base_balance.23.aspx

" In Stewart’s paradigm, H+, OH-, HCO3-, and CO32- are relegated to the status of dependent variables, i.e. they can only be formed from the differential movements and exchanges of independent strong ions (Na+, K+, Cl-) that disturb electroneutrality, which is immediately corrected by the hydrolysis of water and reaction with carbon dioxide."

Base excess: = the amount of strong acid (complete dissociated from H+) needed to restore 1L of blood to pH of 7.4 at 40 mmHg. Used to isolate metabolic component from respiratory compensation.