Approach to acid-base problems in the critically ill and injured.

The use of the Henderson-Hasselbalch equation and the relationships between bicarbonate levels and the pCO2 or carbonic acid concentration in evaluating acid-base abnormalities are explained. The etiology, pathophysiology, diagnosis and treatment of respiratory alkalosis and acidosis and metabolic alkalosis and acidosis are discussed. The results of laboratory tests should be examined in relation to the patient's condition and consistency with other laboratory tests. Therapy is directed at correcting the underlying problems and, secondarily, at correcting the numbers. Patients respond primarily to rate of change and not absolute numbers. Therefore, problems should be corrected at approximately the rate they develop. Treatment should be guided by continued patient observation and serial laboratory studies.