Acid Base Disturbances

Posted by e-Medical PPT
Acid-base disorders are changes in arterial Pco2, serum HCO3 −, and serum pH.
    *Acidemia is serum pH < 7.35.
    *Alkalemia is serum pH > 7.45.
    *Acidosis refers to physiologic processes that cause acid accumulation or alkali loss.
    *Alkalosis refers to physiologic processes that cause alkali accumulation or acid loss.
Actual changes in pH depend on the degree of physiologic compensation and whether multiple processes are present.

Classification
Primary acid-base disturbances are defined as metabolic or respiratory based on clinical context and whether the primary change in pH is due to an alteration in serum HCO3 − or in Pco2.
Metabolic acidosis is serum HCO3 − < 24 mEq/L. Causes are
    *Increased acid production
    *Acid ingestion
    *Decreased renal acid excretion
    *GI or renal HCO3 − loss

Metabolic alkalosis is serum HCO3 − > 24 mEq/L. Causes are
    *Acid loss
    *HCO3 − retention

Respiratory acidosis is Pco2 > 40 mm Hg (hypercapnia). Cause is
    *Decrease in minute ventilation (hypoventilation)

Respiratory alkalosis is Pco2 < 40 mm Hg (hypocapnia). Cause is
    *Increase in minute ventilation (hyperventilation)


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