Effect of halothane and pentobarbital anesthesia on the dispersion of indicator particles passing through the central circulation of the dog

To investigate the effect of different anesthetics on the flow properties of the central circulation, curves were obtained by the multiple indocyanine-green indicator-dilution technic from 7 dogs anesthetized with halothane or pentobarbital. The width of the curve provided a measure of the dispersion of indicator particles during passage through the central circulation. The vascular resistance of the animals was altered by the administration of methoxamine and sodium nitroprusside. The authors found that dispersion in the central circulation is linearly related to the total peripheral resistance (TPR). For any value of TPR, the amount of dispersion of indicator particles passing through the central circulation was greater with halothane plus pentobarbital anesthesia than with pentobarbital only. The study indicates that the type of anesthesia influences the dispersion of indicator particles passing through the central circulation. A better under standing of this process will be helpful in interpreting the results of indicator-dilution cardiac-output determinations performed in persons under general anesthesia.