HALOTHANE REDUCES REPERFUSION INJURY AFTER REGIONAL ISCHEMIA IN THE RABBIT HEART IN-VIVO

In addition to having anti-ischaemic effects, halothane can protect is olated rat hearts and isolated cardiomyocytes against reperfusion inju ry of the ''oxygen paradox'' type. The aim of this study was to invest igate if halothane can also protect against myocardial reperfusion inj ury in vivo. Twenty-two rabbits anaesthetized with alpha-chloralose un derwent 30 min of occlusion of a major coronary artery and 2 h of subs equent reperfusion. Seven animals received 1 MAC of halothane for the first 15 min of reperfusion (halothane group), and eight animals serve d as untreated controls (control group). In seven additional animals, the haemodynamic effects of halothane were antagonized by an i.v., inf usion of noradrenaline (halothane- noradrenaline group). We measured c ardiac output (GO) by an ultrasonic flow probe around the ascending ao rta, left ventricular pressure (LVP) by a tip manometer and infarct si ze by triphenyltetrazolium staining. Baseline LVP was mean 92 (SEM 4) mm Hg and CO was 289 (16) ml min(-1). During coronary occlusion, LVP w as 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 gr oup vs control group). Noradrenaline prevented the reduction in LVP (h alothane-noradrenaline group 87 (5) % of baseline, control group 84 (6 ) %) and reduction in CO (halothane-noradrenaline group 89 (5) %, cont rol 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 ear ly reperfusion period after myocardial ischaemia protected the myocard ium against infarction in vivo, independent of the haemodynamic effect s of halothane.