ENDOTHELIN, ACTH, AND CORTISOL PLASMA-LEVELS IN PATIENTS UNDERGOING AORTOCORONARY BYPASS-GRAFTING

Study objective. To follow up endothelin (ET), adrenocorticotropic hormone (ACTH), and cortisol levels in patients undergoing aortocoronary bypass grafting (CABG) and to determine whether these are extracted from plasma by the pulmonary circulation. Design. Convenience sample trial. Setting. University hospital. Patients. Eight male routine CABG patients without appreciable concomitant disease. Interventions. Patients were given anaesthesia in a strictly standardised manner using etomidate, flunitrazepam, fentanyl, and pancuronium. Nitroglycerin was administered prior to cardiopulmonary bypass (CPB) at 2 mg/h and dopamine as the only catecholamine starting from CPB weaning until the end of sampling at 3.5-5 mug/kg.min. Samples were drawn in rapid sequence from cannulated radial and a distal pulmonary arteries (Swan-Ganz catheter) at eight sampling times starting after induction of anaesthesia and catheter placement and finishing 22 h after the end of operation. Measurements and Results. ET levels were determined by an ET-1, 2, 3-sensitive radioimmuno-assay (RIA), ACTH and cortisol by commercially available RIA kits. There was a significant (P = 0.032, linear regression analysis) correlation between ET and cortisol from pulmonary arterial samples. ET was significantly (P = 0.042, two-tailed Wilcoxon test) extracted by the pulmonary circulation after induction of anaesthesia. This pulmonary-systemic arterial difference nearly disappeared intraoperatively, but tended to be restored 22 h after the end of operation at an approximately twofold increased level. Conclusions. No interrelation between ET and the hypothalamic-pituitary-adrenal axis could be established by the ET, ACTH, and cortisol plasma levels. However, the significant correlation between perioperative ET and cortisol lends further support to the hypothesis of ET release by cortisol from vascular smooth-muscle cells. There is a net pulmonary clearance of ET in patients prior to CABG that is lost intra- and early postoperatively, but tends to be restored on the 1st day thereafter at an increased level.