Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (622 page)

   In clinical setting of respiratory acidosis but with normal blood pH and/or HCO
₃
⁻
higher than predicted, complicating metabolic alkalosis may be present.

   Examples: chronic pulmonary disease with CO
₂
retention developing metabolic alkalosis due to administration of diuretics, severe vomiting, or sudden improvement in ventilation (“posthypercapnic” metabolic alkalosis).

   Metabolic Acidosis with Respiratory Alkalosis

   pH may be normal or decreased.

   Hypocapnia remains inappropriate to decreased HCO
₃
⁻
for several hours or more.

   Examples: Rapid correction of severe metabolic acidosis, salicylate intoxication, gram-negative septicemia, initial respiratory alkalosis with subsequent development of metabolic acidosis. Primary metabolic acidosis with primary respiratory alkalosis with an increased AG is characteristic of salicylate intoxication in the absence of uremia and DKA.

   Metabolic Alkalosis with Respiratory Alkalosis

   Marked alkalemia with decreased pCO
₂
and increased HCO
₃
⁻
is diagnostic.

   Examples: Hepatic insufficiency with hyperventilation plus administration of diuretics or severe vomiting; metabolic alkalosis with stimulation of ventilation (e.g., sepsis, pulmonary embolism, mechanical ventilation), which causes respiratory alkalosis.

   Acute and Chronic Respiratory Acidosis

   
⁻
May be suspected when HCO
₃
^‒
is in intermediate range between acute and chronic respiratory acidosis (similar findings in chronic respiratory acidosis with superimposed metabolic acidosis or acute respiratory acidosis with superimposed metabolic alkalosis)

   Examples: Chronic hypercapnia with acute deterioration of pulmonary function causing further rise of pCO
₂