In so-called anesthetic doses, all benzodiazepines decrease blood pressure and increase heart rate sec­ondary to a decrease in peripheral re­sistance. But exceptionally, with dia-zepam they are reported to be secondary to a decrease in left ven­tricular work and cardiac output. This study was conducted to determine the effect of diazepam in subanesthetic dose on the different phases of cardi­ac work; the rapid, reduced ejection phases of ventricular systole and on the arterial pressure decay after aortic vaive closure. These phases of cardi­ogram were recognized and analyzed using a computer system connected to two biopreamplifiers for arterial pressure and ECG monitoring simul­taneously. Single arterial pressure wave could be magnified for doing dif­ferent estimations for the different
phases of the arterial pressure wave. Two groups of rabbits, each of 6 animals were used to test the effect of diazepam (0.7 mg /rabbit i.v) and the blocking or reversing effects induced by flumazenil (0.02 mg /rabbit i.v.). Each animal served as a control for itself.
Diazepam and not flumazenil de­creased the ejection period as com­pared with that of control {0.56±0.09 Vs 1.00±0.09 msec). This effect was not accompanied by any change in heart rate and cardiac cycle period. Flumazenil blocked this diazepam ef­fect but insignificantly reversed it. In­creased ejection velocity by diazepam was indicated by an increase in the ascending limb slope of the arterial pressure wave (0.6060±0.0367 Vs 0.4845±0.0279) together with un­changed pulse pressure.