Cardiohaemodynamic and plasma level responses to intraoral submucosal injection of adrenaline

Since knowledge of the bioavailability of adrenaline from the intraoral submucosal depot is a prerequisite for its safe use in dentistry, the time-dependent effects of adrenaline on the plasma adrenaline level and cardiohaemodynamic parameters were studied with invasive methods in adrenalectomized, anaesthetized rats after injection of adrenaline (4.0 micrograms/kg body wt) into the mucobuccal fold lateral to the upper right incisor. The absolute bioavailability of adrenaline from this intraoral submucosal depot was 16.8 per cent. Peak values for arterial plasma adrenaline and arterial blood pressure, maximal rate of rise of pressure in the left ventricle and heart rate were measured as early as 5 s after an injection period of 10 s. The different velocities at which the individual parameters returned to the basal state showed that the measurement of heart rate is an insensitive indicator of systemic adrenaline. Due to the absorption kinetics of adrenaline from intraoral tissue it may be concluded that the method of injection has a decisive influence on arterial adrenaline concentration and thus on cardiovascular response.