The role of alpha 1-adrenoceptors in adrenaline-induced hyperkalaemia.

The hyperkalaemic action of adrenaline was investigated in 44 anaesthetized domestic pigs. Plasma and epicardial concentrations of K+ were measured, in the latter case with an ion-selective electrode. Adrenaline 10 micrograms kg-1 caused a rapid increase in the plasma concentration of K+ from 4.2 to 5.9 mmol litre-1. The magnitude and the time course of epicardial concentration of K+ were similar. Alpha-adrenoceptor block with either phentolamine 5 mg kg-1 (non-selective block) or prazosin 0.1 mg kg-1 (selective alpha 1-adrenoceptor block) abolished the hyperkalaemic effect of adrenaline in the plasma and on the epicardium. The alpha 1-adrenoceptor agonist phenylephrine increased the K+ concentration, but the alpha 2-adrenoceptor agonist UK 14.304 did not cause any change in concentration. These results suggest that the hyperkalaemia induced by adrenaline occurs in the interstitial fluid of the myocardium and is mediated by alpha 1-adrenoceptors. These findings may be important in patients at risk of hyperkalaemia, with implications, for example, in the use of suxamethonium during induction of anaesthesia.