2 Metabolic and Respiratory Acid–Base Disorders Free Online FlashCards

What are the typical adult ABG reference ranges?

Typical adult ranges are pH $7.35\text{–}7.45$, PaCO₂ $35\text{–}45\,\mathrm{mm\,Hg}$, and HCO₃⁻ $22\text{–}26\,\mathrm{mEq/L}$; local ranges may vary.

How do pH values identify acidemia and alkalemia?

A pH below $7.35$ is acidemia; a pH above $7.45$ is alkalemia.

How do HCO₃⁻ and PaCO₂ point to a primary disorder?

HCO₃⁻ indicates a primary metabolic process, while PaCO₂ indicates a primary respiratory process. In metabolic disorders, pH and HCO₃⁻ move together; in respiratory disorders, pH and PaCO₂ move oppositely.

What is the typical compensation for metabolic acidosis?

Metabolic acidosis lowers HCO₃⁻; compensation usually lowers PaCO₂ through increased ventilation.

What is the typical compensation for metabolic alkalosis?

Metabolic alkalosis raises HCO₃⁻; compensation usually raises PaCO₂ through decreased ventilation.

How do the kidneys compensate for respiratory acidosis?

Respiratory acidosis raises PaCO₂. The kidneys compensate by retaining HCO₃⁻, with greater compensation developing over days.

How do the kidneys compensate for respiratory alkalosis?

Respiratory alkalosis lowers PaCO₂. The kidneys compensate by excreting HCO₃⁻, with greater compensation developing over days.

What formula estimates expected PaCO₂ in metabolic acidosis?

Use Winter’s formula: $\mathrm{PaCO_2}=(1.5\times\mathrm{HCO_3^-})+8\pm2\,\mathrm{mm\,Hg}$. A measured value outside the predicted range suggests an additional respiratory disorder.

What are common causes of metabolic acidosis?

Common causes include increased acid production, such as lactic acidosis or ketoacidosis; reduced renal acid excretion; and bicarbonate loss, such as with diarrhea.

What are common causes of metabolic alkalosis?

Common causes include acid loss from vomiting or gastric suction, diuretic use, and excess bicarbonate.

What kinds of problems can cause respiratory acidosis?

Inadequate ventilation can cause respiratory acidosis, including from airway or lung disease, sedatives or opioids, and neuromuscular weakness.

What causes should be considered with respiratory alkalosis?

Excessive ventilation may be associated with pain, fever, hypoxemia, pulmonary embolism, pregnancy, or sepsis. Investigate the cause rather than assuming anxiety.