PaCO2 and the Pre-ejection Period: The PaCO2/Inotropy Response Curve

Permissive hypercapnia. How permissive should we be?

“…In these latter conditions, cardiac output did not augment in spite of a significant decrease in systemic vascular resistance and a slight increase in heart rate. This confirms previous data (44,45) suggesting that in the intact animal, the depressant effect of hypercapnia is offset by the stimulating action of CO 2 on the central and autonomic systems.…”

“…The hemodynamic response to inhalation of CO 2 or to acute alveolar hypoventilationin experimental animals and anesthetized human subjects is characterized by an increase in cardiac output, heart rate, and stroke volume, and a decrease in systemic vascular resistance (44,52). This response represents the balance between the depressant effects of CO 2 on mechanical performance and its indirect effects on peripheral chemoreceptors and vasomotor centers, which enhance bothsympathetic nervous activity and catecholamine secretion (16,17).…”

Optimizing the intraoperative management of carbon dioxide concentration

“…Myocardial contractility does not appear to be affected up to a PaCO 2 of 75 mmHg [14]. Hypercapnia directly depresses the myocardium [17,18]. Hypercapnia, however, also stimulates the myocardium indirectly through the sympathetic nervous system activation [18,19].…”

“…Hypercapnia directly depresses the myocardium [17,18]. Hypercapnia, however, also stimulates the myocardium indirectly through the sympathetic nervous system activation [18,19]. In the early 1970s, Blackburn et al [18,20] showed that CO 2 had inotropic effects through β-adrenergic receptors in dogs and human patients.…”

“…Hypercapnia, however, also stimulates the myocardium indirectly through the sympathetic nervous system activation [18,19]. In the early 1970s, Blackburn et al [18,20] showed that CO 2 had inotropic effects through β-adrenergic receptors in dogs and human patients. They concluded that the main effect of hypercapnia on the heart was β-adrenergic receptormediated inotropy, which has a threshold of between 70 and 100 mmHg PCO 2 (Table 1).…”