The influence of lidocaine and verapamil on haemodynamic parameters after intravenous administration of midazolam in rabbits.

Cardiac arrhythmia can be a serious complication during general anaesthesia of patients suffering from cardiac arrhythmias and using antiarrhythmic drugs. The aim of the present experiments was to establish the way in which lidocaine and verapamil influence haemodynamic parameters of rabbits after midazolam anaesthesia. The experiments were performed on rabbits. Heart rate was counted according to ECG. Blood pressure was measured directly in the carotid artery. Cardiac output, stroke volume, and total peripheral resistance were estimated using the method of human 125J albumin dilution. Midazolam caused a gradual fall of arterial blood pressure till 30 min of the experiment. The decrease of blood pressure in the first 45 min of the experiment might be a result of decreasing peripheral resistance, and after 60 min should be rather attributed to a decrease of cardiac output and stroke volume. Lidocaine did not change the influence of midazolam on the blood pressure and heart rate. The consequence was a decrease of blood pressure after midazolam and lidocaine administration. Combined administration of midazolam and lidocaine decreased the influence of both midazolam and lidocaine on the total peripheral resistance. An injection of midazolam with verapamil resulted in a significant decrease of blood pressure. Combined administration of midazolam and verapamil caused a significant decrease of heart rate as compared with the initial value and administration of midazolam alone.