<![CDATA[<b>Effects of diazepam, midazolam, propofol and etomidate in myocardial contractility and coronary blood flow</b>: <b>comparative analysis in isolated rat's hearts</b>]]>

Abstract

Objective: The effects on myocardial contractility (dT/dt max) and coronary blood flow of common drugs used in clinical practice (diazepam, midazolam, propofol and etomidate) were studied. Method: Fifty Wistar rat hearts were divided into five groups of ten and perfused using the Langendorff method with Krebs-Henseleit solution (K-H), with the perfusion pressure stable at 90 cm H 2 O and the temperature at 37.0 ± 0.5 °C. With the exception of Group I (control), they were submitted to single one-minute infusions of diazepam (50 micrograms)-Group II; midazolam (25 micrograms)-Group III; propofol (25 and 50 micrograms)-Group IV and etomidate (25 micrograms)-Group V. The drugs were diluted in 0.1 mL of K-H solution and the coronary blood flow rate and perfusion pressure controlled during infusion. The heart rate (beats per minute), myocardial tension (grams) and coronary blood flow (millimeters per minute) were measured at 1, 3, 5, 10, 15, 20, 25 and 30 minutes. The myocardial contractility was obtained by calculating the first derived tension/time (dT/dt max), at each time interval. Results: The heart rate showed variations in Groups I, III and IV. A variation in the myocardial tension was seen in all groups except Group I and alterations in the coronary blood flow were seen in all groups except Group IV during the experiment. The myocardial contractility decreased in all groups, except for Group I. Conclusion: The assayed drugs diminished the myocardial contractility (p<0.05); the variations of the coronary blood flow were not directly correlated to those that occurred with the myocardial contractility.