Effects of hypocapnia on hemodynamics and myocardial metabolism in anesthetized dogs
Toriumi, S.; Sakata, S.; Matsumoto, Y.; Saito, T.
Masui. Japanese Journal of Anesthesiology 40(4): 544-551
1991
ISSN/ISBN: 0021-4892 PMID: 1904956 Document Number: 375324
The authors previously reported that hypocapnia increased myocardial oxygen demand under droperidol-fentanyl (D-F) anesthesia. In this study we observed myocardial oxygen tension, hemodynamics, and coronary arterial-venous blood content differences of oxygen and lactate before and after hyperventilation in dogs with and without a narrowed coronary artery under halothane anesthesia. We studied the functional and metabolic responses of the heart to hypocapnia under halothane in comparison with D-F anesthesia. In the intact heart, heart rate, LV dp/dt max and myocardial energy demand (heart rate .times. systolic aortic pressure .times. LV dp/dt max), which increased during hypocapnia under D-F anesthesia, were unchanged during hypocapnia under halothane anesthesia. Aortic pressure and coronary flow were unchanged under both types of anesthesia. Though subendocardial oxygen tension decreased significantly, myocardial lactate extraction was unchanged under both types of anesthesia. In the heart with a constricted coronary artery, subendocardial oxygen tension and lactate extraction ratio decreased significantly during hypocapnia under both types of anesthesia. Myocardial lactate production was observed in six of eleven dogs in which myocardial energy demand increased under D-F anesthesia. Myocardial lactate production was observed in one dog under halothane anesthesia. Coronary arterial-venous blood oxygen content difference increased under D-F anesthesia, but not under halothane anesthesia. In summary, hypocapnia increased myocardial oxygen demand under D-F anesthesia but not under halothane anesthesia. In the intact heart under both types of anesthesia, hypocapnia deteriorated myocardial oxygen supply-demand relations, but the evidence of myocardial anaerobic metabolism was not observed. When hypocapnia increases myocardial oxygen demand, there is a possibility that hypocapnia induces myocardial ischemia in the heart with a stenotic coronary artery. It is probable that the adverse effect of hypocapnia on the heart with a stenotic coronary artery is less under halothane anesthesia than under D-F anethesia.