Effects of general anesthetics on the microcirculation.

The potent inhalation anesthetics (halothane, enflurane and isoflurane) have significant influences on the peripheral circulation. The changes in regional blood flows result from a combination of central circulatory effects on cardiac output and arterial pressure and from local microvascular changes in individual organs. The changes are drug-specific, organ-specific, and generally dose-related, so that no simple overall view is reliable and accurate. Some generalizations are possible, however. For example, each of the potent inhalation anesthetics reduces cerebral and cutaneous vascular resistance in a dose-related manner. Each reduces renal blood flow in humans in excess of the reduction in arterial pressure, implying that renal arteriolar constriction occurs with each drug. While the changes in organ blood flow do not result in tissue hypoxia when the circulation is normal, the anesthetics appear to have important microvascular influences during conditions of tissue ischemia such as coronary artery occlusion or hemorrhagic hypotension.