ARRHYTHMIAS, HEMODYNAMIC-CHANGES AND EXTENT OF MYOCARDIAL DAMAGE DURING CORONARY LIGATION IN RABBITS ANESTHETIZED WITH HALOTHANE, ALPHA CHLORALOSE OR PENTOBARBITAL

We investigated the incidence of ventricular arrhythmias, extent of myocardial infarction and alteration in haemodynamic parameters during 30 minutes of coronary arterial occlusion in rabbits anaesthetized with halothane, alpha chloralose and pentobarbitone. Ventricular tachycardia and fibrillation occurred in 10 of 15 given halothane and in 11 of 15 animals given alpha chloralose while of 15 animals given pentobarbitone, 5 developed tachycardia and 8 had fibrillation. Following ligation, blood pressure promptly fell in each group to 71-76% of control values at 1 minute and remained low throughout the occlusion period. This was most marked in the group receiving halothane which had significantly lower pressures at 30 minutes than those anaesthetized with alpha chloralose or pentobarbitone (P < 0.01 in each case). Those receiving halothane also recovered less on reperfusion. Heart rate remained stable with pentobarbitone anaesthesia during coronary occlusion and reperfusion, but promptly declined in the first minute of occlusion in the groups given halothane and alpha-chloralose and then remained low throughout occlusion, especially in the group given alpha-chloralose (P < 0.001 vs pentobarbitone and P < 0.01 vs halothane). The extent of myocardial damage was measured from nitroblue tetrazolium-stained sections and expressed as a percentage of the zone at risk, which was obtained in five hearts following 90 minutes coronary ligation. Values were 44.0% with pentobarbitone, 54.0% with alpha chloralose (P < 0.01 vs pentobarbitone) and 62.1% with halothane (P < 0.001 vs pentobarbitone). Thus, the choice of anaesthetic employed during experimental myocardial ischaemia may have significant effects on the incidence of ventricular tachycardia, haemodynamic changes and extent of necrosis observed. These findings have important implications for the design of experimental models of myocardial ischaemia.