PROTECTIVE EFFECTS OF HALOTHANE BUT NOT ISOFLURANE AGAINST GLOBAL ISCHEMIC-INJURY IN THE ISOLATED WORKING RAT-HEART

The effects of equi-anaesthetic concentrations of halothane (HAL) and isoflurane (ISO) on myocardial performance, perfusion, oxygenation and lactate release were studied before, during and after a low-flow, glo bal ischaemic insult in isolated, paced rat left heart preparations. A n antegrade perfusion technique was used, where left atrial pressure ( LAP) and mean aortic pressure (MAP) could be altered independently of each other. Aortic flow, coronary flow (CF) and PO2 in venous coronary effluent were continuously recorded and stroke volume, myocardial oxy gen consumption (MVO(2)) and myocardial oxygen extraction as well as l actate release were calculated. The hearts were exposed for at least t en minutes to the perfusate without (control, n=10) or with HAL (n=10) or ISO (n=10) at a MAP of 80 mmHg (10.4 kPa) and a LAP of 7.5 mmHg (1 .0 kPa). After baseline measurements, MAP was reduced to 25 mmHg (3,2 kPa) for a total of nine minutes. Thereafter MAP was increased to 80 m mHg (10.4 kPa) for another nine minute period. During the whole experi mental procedure, LAP was maintained at 7.5 mmHg (1.0 kPa) and heart r ate at 325 beats per minute. In the pre-ischaemic control period, MVO( 2) was lower with HAL, compared to ISO (P<0.05) and control (P<0.05). Stroke volume was also lower with HAL compared to control (P<0.05). Du ring hypoperfusion, lactate release was twice as high in the control g roup (P<0.01) and with ISO (P<0.01) compared to HAL. This was accompan ied by a lower oxygen extraction with HAL compared to control (P<0.05) and ISO (P<0.05). Tn the post-ischaemic periods, MVO(2) and stroke vo lume were lower with HAL compared to ISO and control. There were no si gnificant differences in CF between the groups. We conclude that HAL, but not ISO, exerts a direct protective effect against a glycotic anae robic metabolism during low-flow global myocardial ischaemia.