Effects of acute hypercapnia and hypocapnia on plasma and red cell potassium, blood lactate and base excess in man during anesthesia.

In order to test the relationship between changes in plasma potassium concentration and pH changes of respiratory origin, we produced hypercapnia (mean PaCO2 71 mmHg = 9.5 kPa) in a group of 17 patients and hypocapnia (mean PaCO2 21 mmHg = 2.8 kPa) in another 20 patients during neurolept analgesia and intraabdominal operations. A control group of 19 patients was studied under normocapnia but otherwise identical conditions. During hypercapnia, serum potassium rose, deltaK/deltapH amounting to -0.82, -1.05 and -1.34 after 30, 60 and 90 min, respectively. During hypocapnia, serum potassium decreased, deltaK/deltapH being a little more negative than during hypercapnia (mean values -1.62, -2.44 and -1.60). Red cell potassium concentration decreased in all three groups to a similar extent. Blood lactate levels during hypercapnia decreased to 75% of control and during hypocapnia rose to a maximum of 186% of control. In order to obtain reasonable values for base excess in primarily respiratory acid-base disorders, it is necessary to use nomograms based on in vivo ECF-CO2-titration curves. With this premise, hypercapnia or hypocapnia in our patients was not associated with significant changes in base excess.