Effects of lidocaine on myocardial function and on isoprenaline-induced circulatory changes in man.
14 non-cardiac patients aged 42 to 71 years (mean 49 years) were studied. Part I 1 mg/kg or 2 mg/kg of lidocaine were administered i.v. on two consecutive days and systolic time intervals (STI) were obtained at one minute intervals for 30 minutes. No change in STI was observed after lidocaine injection. In Part II, a bolus of 5 mug of isoprenaline was given i.v. before and after an injection of 2 mg/kg of lidocaine. Isoprenaline caused a highly significant increase in the heart rate, shortening of the total electromechanical systole, pre-ejection period, electromechanical delay, isovolumic contraction time as well as PEP/LVET and ICT/QS1, indices (in all cases p less than 0.001). 2 mg/kg lidocaine had no blocking or potentiating action on the catecholamine-induced circulatory changes. In Part III, after the isoprenaline challenge, a dose of 2 mg/kg of lidocaine was administered and the bolus injection was followed by an infusion of 30 mug/kg/min. Lidocaine per se caused no change in STI in the course of the infusion over 90 minutes, and there was no difference between isoprenaline-induced changes in STI before and during lidocaine infusion. These results suggest that lidocaine has no negative inotropic effect in the therapeutic dose range in man. Lidocaine caused no change in the systolic time intervals, it had no blocking or potentiating action on the isoprenaline-induced circulatory changes, and it had no negative inotropic effect in therapeutic doses in man.