Acid/Base Overview

Regular pH of blood = 7.4

  • pH may decrease as a result of increased concentration of H+ ions
    • an increased concentration of H+ may occur as a result of an accumulation of acids and/or a loss of bases in the body
  • pH may increase as a result of decreased concentration of H+ ions
    • a decreased concentration of H+ may occur as a result of an accumulation of bases and/or a loss of acids in the body

Bicarbonate/carbonic acid buffer system   (Bicarbonate is the main buffer of pH in the blood)

  • CO2 « CO2 (dissolved) + H2O « H2CO3 « H+ + HCO3-
  • pH = pKa + log [base]/[acid]
  • pH = pKa + log HCO3-/H2CO3
    • If the [HCO3-] and pCO2 are increased or decreased proportionately the ratio remains fixed and the pH is not affected

Arterial blood gas (ABG) components: pH/PCO2/pO2/[HCO3-]

  • Normal Ranges in the human body:
    • pH = 7.35-7.45
    • pCO2 = 35-45 mm Hg
    • pO2= 80-100 mmg Hg
    • HCO3 = 22-26 mEq/L

Anion gap (AG) = [Na] – ([Cl-] + [HCO3-])

  • Normal AG range in the human body = 10-12 mEq/L

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