The article “Assessing Tissue Oxygenation” (June 2002:22–40) contains a comprehensive overview of arterial blood gas analysis, which will prove to be a valuable resource for nurses and other healthcare professionals in the intensive care environment. The steps outlined are useful in determining an acid-base imbalance involving either the metabolic or respiratory systems and the effectiveness of attempted compensation. However, severely ill patients who develop multiple organ failure frequently present with several acid-base abnormalities occurring simultaneously. Therefore, I routinely add an additional step in the analysis of arterial blood gases to determine if another primary acid-base process is present.
The purpose of the additional step is to determine the expected compensation for the primary disorder. If the actual compensation falls within the calculated range, then a second disorder does not coexist. If the calculated value does not match the measured value, then a mixed disorder is present or compensation has not...