The influence of isoflurane on systemic vascular resistances was studied during total cardiopulmonary bypass with membrane oxygenator, low rate of 2.4 L/min/㎡ and moderate hypothermia. Data were obtained from 40 adult patients undergoing
corrective
surgery for congenital or aquired heart disease. The materials were randomly divided in two groups with 20 and 20 patients, respectively, Before cadiopulmonary bypass, the same anesthetic technique was applied to 2 groups.
During cardiopulmonary bypass, isoflurane was given into oxygenator at 0.5-1.5% concentration in group I . In group II, no isoflurane was given but 0.2 mg/kg midazolam was supplied into the oxygenator at the beginning of bypass. To both groups
small
amounts of fentanyl were given during bypass.
There were no significant differences in mean cardiopulmonary bypass time and pump flow between the groups. In group I , systemic vascular resistance did not increase until 60 minutes, whereas in group II systemic vascular resistance increased
significantly after 30 minutes and maximal increase was noticed at 60 minutes. Data for base excess demonstrated that significant fall after 40 minutes of perfusion in group II, but not changes in group I.
It is concluded that isoflurane exerts a beneficial vasodilatory action during cardiopulmonary bypass and hypothermia. And the harzards of local reduction in organic blood flow are eliminated, because an adequate perfusion pressure and flow are
maintained by the heart lung machine.
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