Negative inotropic effects of halothane, enflurane, and isoflurane in papillary muscles from diabetic rats

Myocardial contractile responses to halothane, enflurane, and isoflurane were studied in papillary muscles isolated from streptozotocin-induced diabetic rats and in those from age-matched control rats. The developed tension in diabetic papillary muscles electrically paced at a constant rate was not different from that in control muscles, but both the time to peak tension and the relaxation time of the isometric contraction were significantly prolonged in diabetic muscles. Halothane, enflurane, and isoflurane all produced negative inotropic effects in both diabetic and control muscles. However, the negative inotropic effects were significantly less in the muscles from diabetic rats than in the muscles from control rats throughout the range of concentrations. In muscles from both the diabetic and control rats, the negative inotropic effects of these anesthetics were accompanied by decreases in the time to peak tension and in relaxation time. The results suggest that the myocardium from the diabetic rat is less sensitive to the negative inotropic action of volatile anesthetics than is the myocardium of normal hearts.