[Is adrenaline in a 2% lidocaine solution after enoral injection hemodynamically effective?]

Adrenaline in local anesthetic solutions is thought to be the causative factor of acute exacerbations of preexisting cardiac diseases during dental anesthesia. This assumption presupposes the systemic effectiveness of adrenaline when coinjected with a local anesthetic drug. To test the above assumption, cardiovascular effects (PS, PD, dP/dTmax LVEP, CO, HR, EGG) and arterial drug concentrations were measured before and after injection of 1.0 ml/kg b.w. of a 0.9% NaCl, 1:300,000/1:100,000 adrenaline-HCl or 2% lidocaine-HCl alone and in combination into the mucobuccal fold of adrenalectomized rats. The transient increase in the cardiovascular parameters by adrenaline was abolished by lidocaine coinjection. The cardiodepressant effect of plain lidocaine was only reversed by the higher adrenaline dose, which however induced a small fall in PD, R and PM. Lidocaine increased the bioavailability of adrenaline from the intraoral depot. Inhibition of COMT activity by lidocaine may contribute to this effect. These findings demonstrate no cardiac response to adrenaline, up to 1:100,000 in a 2% lidocaine solution. In agreement with clinical findings the 1:100,000 adrenaline containing solution can be safely used in compromised cardiovascular patients. However, an interaction between a vasoactive comedication and lidocaine/adrenaline on the vascular system has to be taken into consideration.