Interaction between calcium channel blockers and volatile anaesthetics in the rat heart-lung preparation

We have studied the effects of the calcium channel blockers verapamil, diltiazem and nifedipine and the volatile anaesthetics halothane, enflurane and isoflurane on myocardial metabolism after postischaemic reperfusion in the rat isolated heart-lung preparation. In the presence of the volatile anaesthetics, the preparations were perfused for 10 min, made globally ischaemic for 8 min, and then reperfused for 10 min. Each of the calcium blockers was administered 5 min before ischaemia. Three hearts in the halothane-verapamil group (n = 10) failed to recover from the ischaemia and the recovery time in the same group was significantly longer than in the enflurane-verapamil or isoflurane-verapamil groups. Although there was no significant difference in myocardial lactate concentrations among the groups, ATP and glycogen contents in the halothane-verapamil group were significantly less than those in the other groups. The results suggest that the combination of halothane and verapamil causes significant myocardial depression during recovery from ischaemia and subsequent metabolic deterioration.