In the early postoperative period after coronary artery bypass surgery, arterial hypertension commonly occurs which requires intravenous vasodilator therapy. Purine adenosine is a potent vasodilator and when exogenously administered it decreases systemic arterial blood pressure effectively. We evaluated the effects of adenosine on central hemodynamics and renal function when used to control postoperative hypertension after coronary artery bypass grafting (CABG). Two separate series of experiments were performed postoperatively in the Intensive Care Unit (ICU). In the first study (n = 10), postoperative hypertension was controlled in the rewarming phase, with sodium nitroprusside (SNP, 1.7 +/- 0.4 micrograms.kg-1 x min-1) or adenosine (147.2 +/- 38.9 micrograms.kg-1 x min-1) to keep mean arterial systolic pressure at approximately 80 mm Hg. In the second study on a separate group of patients (n = 9), low doses of adenosine (0, 30, 60, 90, and 0 micrograms.kg-1 x min-1) were infused when the patients were normotensive and rewarmed. Central hemodynamics, urine flow (UF), renal blood flow (RBF), glomerular filtration rate (GFR), and ECG were evaluated during periods of 30 min for each drug in the first study and during each dose of adenosine in the second study. RBF and GFR were determined using standard urinary clearance methods for 51Cr-ethylenediaminetetraacetic acid and p-aminohippuric acid. In the first study, adenosine infusion, compared to SNP, decreased (A - V)O2, increased central filling pressures and heart rate, and caused a more pronounced ST segment depression. During adenosine administration RBF (-44%), GFR (-52%), and UF (-76%) decreased, while renal vascular resistance and filtration fraction (FF) were unaltered compared to data obtained during SNP infusion.(ABSTRACT TRUNCATED AT 250 WORDS)