Respiratory alkalosis: renal compensation

Respiratory alkalosis is due to increased alveolar ventilation relative to carbon dioxide production. Acute hypocapnia causes a reduction of serum levels of potassium and phosphate secondary to increased cellular uptake of these ions. Often, calcium is decreased secondary to increased binding to albumin. During prolonged respiratory alkalosis, bicarbonate ions are actively transported out of CSF, which causes central chemoreceptors to reset to a lower PaCO₂.

The expected change in serum bicarbonate is:

• Acute – [HCO₃-] falls 1-2 mEq/L for each 10 mm Hg decrease in the PaCO₂
• Chronic – [HCO₃-] falls 4-5 mEq/L for each 10 mm Hg decrease in the PaCO₂

Treatment of chronic respiratory alkalosis is aimed at correcting the underlying disorder. More acute respiratory alkalosis can be corrected during anesthesia by decreasingminute ventilation.