[Cardiac and peripheral vascular effects of the volatile inhalational anaesthetic enflurane in chronically instrumented dogs (author's transl)].

While enflurane is generally held to induce arterial hypotension, its overall effects on left ventricular (LV) performance are less clear. Accordingly, mongrel dogs were chronically instrumented with miniature LV pressure transducers, with aortic and left atrial catheters and with electromagnetic flow probes and hydraulic cuff occluders on a common iliac artery. A pair of ultrasonic transducers was implanted on opposing endocardial surfaces to measure LV internal minor axis diameter. Experiments were performed 2 to 9 weeks after surgery when the animals were resting quietly without premedication. Enflurane (2 and 4 vol.-%) decreased mean arterial pressure by 27% and 36% and led to a progressive, dose-dependent decrease in myocardial contractility and induced striking peripheral vasodilatation, i.e. LV-dP/dtmax was reduced by 32% and 54% and iliac conductance rose by 101% and 163%. However, the decrease in contractility was not associated with an increase in LV preload, i.e. LV-end-diastolic diameter was decreased by 2 vol.-%, while it was not significantly different from control values with 4 vol.-%. Thus, in intact chronically instrumented dogs the direct negative inotropic effect of enflurane is modified by a synchronous decrease in myocardial loading conditions.