Hemodynamic dose-response curves and MAC, apneic and lethal concentrations for halothane were determined in two groups of dogs at a normal hematocrit (Hct) (39 ± 6), and during acute anemia (n = 4) and subacute anemia (n = 41, with a combined Hct of 18 ± 6. The ratio of subendocardial/subepicardial blood flow was determined by the injection of radioactive microspheres.
MAC, apneic, and lethal concentrations of halothane were not significantly different in anemic animals. There were also no differences in the halothane dose-response curves plotted for cardiac output, blood pressure, heart rate, left ventricular end-diastolic pressure, or arterial base excess. In 32 microsphere injections with Hct as low as 13, no dog had redistribution of myocardial blood flow suggestive of subendocardial ischemia. We conclude that halothane is a safe anesthetic during severe anemia.