DIRECT CARDIAC EFFECTS IN ISOLATED-PERFUSED RAT HEARTS MEASURED AT INCREASING CONCENTRATIONS OF MORPHINE, ALFENTANIL, FENTANYL, KETAMINE, ETOMIDATE, THIOPENTONE, MIDAZOLAM AND PROPOFOL

The direct cardiac effects of morphine, alfentanil, ketamine, etomidat e, thiopentone, midazolam and propofol were measured in isolated Wista r rat hearts. Experiments were performed using a multiple columnar Lan gendorff apparatus and the hearts were perfused with a modified Tyrode solution under constant pressure. Each drug was applied from a differ ent column in rising concentrations at 5-min intervals. Dose ranges we re chosen to compare effects at subclinical, clinically relevant and m ore than clinical concentrations. Six rat hearts were chosen at random for each drug. Only thiopentone reduced contractile force at a clinic ally relevant concentration: measured as g contractility per g heart w eight(-1) (mean+/-standard deviation), base-line contractility was 8.8 +/-2.4, and contractility at 10(-4) mol litre(-1) thiopentone was 7.1/-1.5 (P<0.01). Alfentanil was the only drug to have no significant ef fect on the isolated heart at any concentration. Propofol was not card iodepressant at clinically relevant concentrations, but had a lower th erapeutic range than the other drugs.