EFFECTS OF FENTANYL, DROPERIDOL, AND INNOVAR ON CANINE CEREBRAL METABOLISM AND BLOOD FLOW

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Abstract
The effects of droperidol and fentanyl given individually and in combination (Innovar) on the rate of cerebral oxygen consumption (CMRo,) and cerebral blood flow (c.b.f.) were studied in dogs anaesthetized with nitrous oxide (70 percent) and oxygen. Fentanyl (0.006 mg/kg) decreased both the CMRo, and the c.b.f. (mean decreases at 15 minutes were 18 per cent and 47 percent, respectively). The duration of effect was approximately 30 minutes. Droperidol (0.3 mg/kg) produced a decrease of 40 per cent in c.b.f. due primarily to a 30-40 per cent increase in cerebrovascular resistance, and this effect persisted for the period of observation (60 minutes). No significant change in CMRo, occurred after droperidol was administered. With the combination drug (Innovar), the effects were partially additive. After 15 minutes, CMRo, had decreased 23 per cent; c.b.f. had decreased 50 per cent; and cerebral vascular resistance had increased 85 per cent. After 30 minutes, the effects of Innovar were indistinguishable from those of droperidol alone. No significant changes occurred in the rate of cerebral glucose consumption or the oxygen-glucose index. The effect of increased and decreased Paooj on c.bi. after Innovar was compared widi that observed during halothane anaesthesia. With halothane, hypercapnia (Pacoi=60 tnm Hg) increased c.b.f. 40 per cent and hypocapnia (Pace = 20 mm Hg) decreased c.b.f. 40 per cent. Innovar at normocapnia reduced the c.b.f. 65 per cent. With hypercapnia, the c.bi. doubled, but with hypocapnia, little further reduction in c.b.f. occurred. It is concluded that droperidol is a potent cerebral vasoconstrictor, that this effect dominates when it is given in combination with fentanyl, that hypocapnia causes little further reduction in c.b.f., and that the reduction in c.bi. produced by Innovar is not accompanied by alterations in normal cerebral metabolic pathways

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