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

In addition to having anti-ischaemic effects, halothane can protect isolated rat hearts and isolated cardiomyocytes against reperfusion injury of the ''oxygen paradox'' type. The aim of this study was to investigate if halothane can also protect against myocardial reperfusion injury in vivo. Twenty-two rabbits anaesthetized with alpha-chloralose underwent 30 min of occlusion of a major coronary artery and 2 h of subsequent reperfusion. Seven animals received 1 MAC of halothane for the first 15 min of reperfusion (halothane group), and eight animals served as untreated controls (control group). In seven additional animals, the haemodynamic effects of halothane were antagonized by an i.v., infusion of noradrenaline (halothane- noradrenaline group). We measured cardiac output (GO) by an ultrasonic 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). During coronary occlusion, LVP was reduced to 86 (4) % of baseline and CO to 84 (4) % (similar in all groups). During halothane administration at reperfusion, LVP declined further to 55 (6) % of baseline and CO to 66 (9)% (P<0.05 halothane group vs control group). Noradrenaline prevented the reduction in LVP (halothane-noradrenaline group 87 (5) % of baseline, control group 84 (6) %) and reduction in CO (halothane-noradrenaline group 89 (5) %, control group 83 (6) %). Infarct size was 49 (6) % of the area at risk in controls and was reduced markedly by administration of halothane to 32 (3) % in the halothane group (P<0.05) and to 30 (3)% in the halothane-noradrenaline group (P<0.05). Treatment with halothane during the early reperfusion period after myocardial ischaemia protected the myocardium against infarction in vivo, independent of the haemodynamic effects of halothane.