Lidocaine reduces ischaemic but not reperfusion injury in isolated rat heart

The local anaesthetic lidocaine protects the myocardium in ischaemia-reperf usion situations. It is not known if this is the consequence of an anti-isc haemic effect or an effect on reperfusion injury. Therefore, we investigate d the effect of two concentrations of lidocaine on myocardial ischaemia-rep erfusion injury and on reperfusion injury alone. We used an isolated rat he art 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 in fusion started 5 min before low-flow ischaemia. In all groups, lidocaine ad ministration was stopped after 15 min of reperfusion. One group served as a n untreated control (n=11 in each group). Left ventricular developed pressu re (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 fro m 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 significant ly different from control (130 (8) IU (P <0.05)). Lidocaine given during ea rly 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(1 56 (21) IU (P=0.50) and 106 (14) IU (P=0.57)). We conclude that lidocaine p rotects the myocardium against ischaemic but not against reperfusion injury in the isolated rat heart.