The biological activity of adrenaline after injection through an intravenous cannula containing alkaline buffer

Abstract

Since it is known that alkaline pH inactivates adrenaline it has been recommended that this drug not be administered in the same i.v. line as alkaline buffer solutions during cardiopulmonary resuscitation. In order to test the validity of this statement a simulation model of the clinical situation was designed where the biological activity of adrenaline was measured in anesthetized rats after having been mixed with alkaline buffer solution contained in a standard i.v. cannula. The biological activity of adrenaline was measured by comparing the blood pressure response after repeated administration of a test (adrenaline + alkaline buffer) and control (adrenaline + normal saline) solution to a rat which had previously received a ganglion-blocking agent. Two alkaline buffer solutions, sodium bicarbonate and Tris buffer mixture were tested. These resulted in a decrease of the biological effect of adrenaline to 77 +/- 6 and 82 +/- 9% of control values, respectively. If however, adrenaline mixed with Tris buffer mixture was injected into a recipient of phosphate buffer (pH 7.40 and buffer capacity equal to human blood) as much as 94 +/- 17% of its activity remained. The results lead us to suggest that, in the cardiopulmonary resuscitation situation, adrenaline may well be given via a cannula containing alkaline buffer solution without significant interference with its effect.