Arterial blood gases fail to reflect acid-base status during cardiopulmonary resuscitation: a preliminary report.

The American Heart Association's current standards for CPR indicate that acid-base therapy should be guided by measurements of arterial blood gases. However, we have discovered a striking discrepancy between arterial and venous blood gases during CPR: severe venous hypercarbia and acidosis may coexist with simultaneous arterial alkalosis. Arterial blood gases during CPR, therefore, may not accurately reflect the acid-base status of mixed venous blood and thus may fail to indicate systemic acid-base status.