| Abstract | Most anesthetic agents affect the coronary circulation indirectly by their effects upon systemic hemodynamics and by their effect on inotropy. Since almost every anesthetic decreases inotropy in a dose-dependent fashion, oxygen requirements and hence myocardial blood flow can be expected to decrease in parallel to the administered dose. The coronary circulation is autoregtilated within a wide range of perfusion pressures. This range may be altered by significant coronary stenoses which restrict vasodilator reserve and by increases in coronary back pressure. In the presence of maintained autoregulation, alterations in myocardial oxygen requirements are, met by changes in coronary blood flow. Hence, myocardial oxygen extraction remains unaltered. Myocardial oxygen extraction may increase to compensate for an insufficient coronary flow response to a rise in energy demands. Conversely, a decline in myocardial oxygen extraction indicates flow in excess of demand, e.g. coronary vasodilatation. Recent data indicate that some anesthetics interfere with normal coronary autoregulation. It is also evident that surgical stimulation and other noxious stimuli may override normal autoregulation. This abstract presents a summary of the effects of common anesthetic agents upon the coronary circulation andmyocardial metabolism. |
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