A mechanically ventilated ICU patient has ABG: pH 7.52, PaCO2 28 mmHg, HCO3- 22 mEq/L. What is the primary disorder and is compensation appropriate?

• A Primary respiratory alkalosis; renal compensation appropriate (expected HCO3- 20–21 mEq/L for acute) ✓
• B Primary metabolic alkalosis with respiratory compensation
• C Mixed respiratory alkalosis and metabolic alkalosis
• D Primary respiratory alkalosis with inadequate renal compensation

Explanation

pH 7.52 (alkalosis), PaCO2 28 mmHg (low — respiratory alkalosis is the primary disorder). For acute respiratory alkalosis, expected fall in HCO3-: 2 mEq/L per 10 mmHg fall in PaCO2. PaCO2 fell by 12 mmHg → expected HCO3- ≈ 24 − 2.4 ≈ 21.6 mEq/L. Measured HCO3- is 22 — consistent with acute respiratory alkalosis with appropriate acute compensation. No additional metabolic component is present.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.