ADRENALINE, CYCLIC-AMP AND POTASSIUM DURING GENERAL-ANESTHESIA WITH AND WITHOUT EPIDURAL ANALGESIA

Twenty patients undergoing abdominal surgery under general anaesthesia were studied to determine whether beta(2)-adrenergic receptor sensiti vity and adrenaline-induced hypokalaemia are related to preceding adre nergic stress. Half of the patients were given epidural analgesia with bupivacaine-adrenaline before starting surgery and then a booster dos e after 60 min of surgery. The others were given only the epidural dos e of bupivacaine-adrenaline at 60 min. Despite marked increases in the plasma adrenaline concentration after the intra-operative epidural do se, there was no decrease in the serum potassium concentration in eith er group. In the patients who received only the 60 min dose, the plasm a adrenaline concentrations increased more, but the plasma level of cy clic AMP (a marker for beta 2-stimulation) increased similarly, which suggests that beta(2)-adrenoceptor responsiveness was somewhat reduced . After the intraoperative bupivacaine-adrenaline, the T wave amplitud e decreased, but neither U waves nor tachycardia developed. In conclus ion, adrenergic stimulation during surgery does not decrease the serum potassium concentration, regardless of whether the surgical stress re sponse has been modified by epidural analgesia. This lack of a hypokal aemic effect might be partly due to reduced responsiveness of beta(2)- adrenoceptors to adrenaline.