Abstract
The manner in which general anesthesia affects circulatory control was studied by examining the effects of commonly employed anesthetics on left ventricular function and distribution of cardiac output, and the extent to which responses to physiological and pharmacological stimuli are modified by general anesthesia. While commonly employed anesthetics affect almost every aspect of the circulatory system, the importance of general anesthesia on the circulation tends to be underestimated by considering only its direct effects. More important is the modification of the organism's integrative response to any perturbation. Major differences often directionally opposite, in responses of conscious and anesthetized animals were found for reflex control of the circulation, effects of hemorrhage and alterations in preload and after load. In addition, commonly employed pharmacologic agents, e.g., cardiac glycosdies, catecholamines, and morphine sulfate exerted differing actions in the conscious and anesthetized states. Thus, while it is generally held that the overall responses to complex physiological functions such as exercise or eating can be best described in the intact, conscious organism, the importance of conducting any experiment involving integrative control of the circulation in the conscious organism should also be recognized.