One MAC of sevoflurane provides protection against reperfusion injury in the rat heart in vivo

Volatile anaesthetics protect the heart against reperfusion injury. We inve stigated whether the cardioprotection induced by sevoflurane against myocar dial reperfusion injury was concentration-dependent. Fifty-eight alpha -chl oralose anaesthetized rats were subjected to 25 min of coronary artery occl usion followed by 90 min of reperfusion. Sevoflurane was administered for t he first IS min of reperfusion at concentrations corresponding to 0.75 (n=1 1), 1.0 (n=11), 1.5 (n=13), or 2.0 MAC (n=12). Eleven rats served as untrea ted controls. Left ventricular peak systolic pressure (LVPSP, tipmanometer) and cardiac output (CO, flowprobe) was measured. Infarct size (IS, triphen yltetrazolium staining) was determined as percentage of the area at risk. B aseline LVPSP was 131 (126-135) mm Hg (mean (95% confidence interval)) and CO 33 (31-36) ml min(-1), similar in all groups. During early reperfusion, sevoflurane reduced LVPSP in a concentration-dependent manner to 78 (67-89) % of baseline at 0.75 MAC (not significant VS controls 99 (86-112)%), 71 (6 2-80)% at I MAC (P<0.05), 66 (49-83)% at 1.5 MAC (P<0.05) and 56 (47-65)% a t 2 MAC (P<0.05). CO remained constant. While 0.75 MAC of sevoflurane had n o effect on IS (34 (27-41)% of the area at risk) compared with controls (38 (31-45)%, P=0.83), 1.0 MAC reduced IS markedly to 23 (17-30)% (P<0.05). In creasing the concentration to 1.5 MAC (23 (17-30)%) and 2 MAC (23 (13-32)%, both P<0.05 vs controls) had no additional protective effect. One MAC sevo flurane protected against myocardial reperfusion injury. Increasing the sev oflurane concentration above I MAC resulted in no further protection.