Lidocaine reduces ischaemic but not reperfusion injury in isolated rat heart

The local anaesthetic lidocaine protects the myocardium in ischaemia-reperfusion situations. It is not known if this is the consequence of an anti-ischaemic effect or an effect on reperfusion injury. Therefore, we investigated the effect of two concentrations of lidocaine on myocardial ischaemia-reperfusion injury and on reperfusion injury alone. We used an isolated rat heart model where heart rate, ventricular volume and coronary flow were kept constant. Hearts underwent 45 min of low-flow ischaemia followed by 90 min reperfusion. Two groups received lidocaine 1.7 or 17 mug ml(-1) starting 5 min before the onset of reperfusion. In two additional groups, lidocaine infusion started 5 min before low-flow ischaemia. In all groups, lidocaine administration was stopped after 15 min of reperfusion. One group served as an untreated control (n=11 in each group). Left ventricular developed pressure (LVDP) and total creatine kinase release (CKR) were measured. Lidocaine administration during ischaemia and reperfusion led to an improved recovery of LVDP during reperfusion (1.7 mug ml(-1), 54 (SEM 10) mm Hg; 17 mug ml(-1). 71 (9) mm Hg at 30 min of reperfusion; both significantly different from control (21 (4) mm Hg) (P<0.05)) and a reduced CKR(1.7 <mu>g ml(-1), 79 (13) IU; 17 mug ml(-1), 52 (8) IU at 30 min of reperfusion; both significantly different from control (130 (8) IU (P <0.05)). Lidocaine given during early reperfusion only, affected neither LVDP during reperfusion (1.7 mug ml(-1), 19 (6) mm Hg (P= 1.0); 17 mug ml(-1), 36 (8) mm Hg (P=0.46)) nor CKR(156 (21) IU (P=0.50) and 106 (14) IU (P=0.57)). We conclude that lidocaine protects the myocardium against ischaemic but not against reperfusion injury in the isolated rat heart.