Halothane reduces reperfusion injury after regional ischaemia in the rabbit heart in vivo

In addition to having anti-ischaemic effects, halothane can protectisolated rat hearts and isolated cardiomyocytes against reperfusion injuryof the "oxygen paradox" type. The aim of this study was to investigate ifhalothane can also protect against myocardial reperfusion injury in vivo.Twenty-two rabbits anaesthetized with alpha- chloralose underwent 30 min ofocclusion of a major coronary artery and 2 h of subsequent reperfusion.Seven animals received 1 MAC of halothane for the first 15 min ofreperfusion (halothane group), and eight animals served as untreatedcontrols (controls group). In seven additional animals, the haemodynamiceffects of halothane were antagonized by an i.v. infusion of noradrenaline(halothane- noradrenaline group). We measured cardiac output (CO) by anultrasonic flow probe around the ascending aorta, left ventricular pressure(LVP) by a tip manometer and infarct size by triphenyltetrazolium staining.Baseline LVP was mean 92 (SEM 4) mm Hg and CO was 289 (16) ml min-1. Duringcoronary occlusion, LVP was reduced to 86 (4)% of baseline and CO to 84(4)% (similar in all groups). During halothane administration atreperfusion, LVP declined further to 55 (6)% of baseline and CO to 66 (9)%(P < 0.05 halothane group vs control group). Noradrenaline prevented thereduction in LVP (halothane-noradrenaline group 87 (5)% of baseline,control group 84 (6)% and reduction in CO (halothane- noradrenaline group89 (5)%, control group 83 (6)%. Infarct size was 49 (6)% of the area atrisk in controls and was reduced markedly by administration of halothane to32 (3)% in the halothane group (P < 0.05) and to 30 (3)% in thehalothane-noradrenaline group (P < 0.05). Treatment with halothaneduring the early reperfusion period after myocardial ischaemia protectedthe myocardium against infarction in vivo, independent of the haemodynamiceffect of halothane.