ANESTHETIC-INDUCED PRECONDITIONING - PREVIOUS ADMINISTRATION OF ISOFLURANE DECREASES MYOCARDIAL INFARCT SIZE IN RABBITS

Background: Experimental evidence suggests that ATP-sensitive potassiu m channels are involved in myocardial ischemic preconditioning, Becaus e some pharmacologic effects of isoflurane are mediated by K-ATP chann els, the authors tested the hypothesis: Isoflurane administration, bef ore myocardial ischemia, can induce or mimic myocardial preconditionin g. Methods: Myocardial infarct size was measured in three groups of pr opofol-anesthetized rabbits, each subjected to 30 min of anterolateral coronary occlusion followed by 3 h of reperfusion. Groups differed iu their pretreatment: Group I (control, N = 13) no pretreatment, Group 2 (ischemic preconditioning, N = 8), 5 min of coronary occlusion and 1 5 min of reperfusion; Group 3 (isoflurane pretreatment; N = If), If mi n of isoflurane (1.1% end-tidal) and 15 min of washout. Hemodynamics w ere monitored serially. Myocardial infarct size and the area at risk w ere defined using triphenyltetrazolium chloride staining and fluoresce nt microspheres, respectively, and both were measured using computeriz ed planimetry. Results: Infarct size ex-pressed as a percentage of are a at risk was 23.4 +/- 8.5% (mean +/- SD in the isoflurane group compa red with 33.1 +/- 13.3% in controls, and 8.7 +/- 6.2% in the ischemia- preconditioned group. Analysis for coincidental regressions, followed by tests for equality of slope and elevation, showed that the linear r elationship between infarct size and area at risk was significantly CP < 0.05) different in all three groups because of differences in line elevation, Minor differences in hemodynamic variables were found betwe en groups, which were unlikely to account for the significant differen ces in infarct size, Conclusion: Preadministration of isoflurane, befo re myocardial ischemia, reduces myocardial infarct size, and mimics my ocardial preconditioning. (Rev words: Heart: ischemic preconditioning; myocardial infarction; myocardial ischemia. Anesthetics, volatile: is oflurane. Potassium channel: ATP-sensitive.)