VASODILATION WITH ADENOSINE OR SODIUM-NITROPRUSSIDE AFTER CORONARY-ARTERY BYPASS-SURGERY - A COMPARATIVE-STUDY ON MYOCARDIAL BLOOD-FLOW ANDMETABOLISM

The effects of adenosine and sodium nitroprusside (SNP) on central hem odynamics and myocardial blood flow and metabolism were investigated p ostoperatively after elective coronary artery bypass (CABG) surgery in ten sedated and mechanically ventilated patients in the intensive car e unit. During three consecutive 15-min periods, SNP (0.8 +/- 0:1 mug. kg-1.min-1), adenosine (88.9 +/- 13.3 mug.kg-1.min-1), and then again SNP (0.7 +/- 0.1 mug.kg-1.min-1) were infused to control postoperative hypertension at a mean arterial pressure of approximately 80 mm Hg. S ystemic and pulmonary hemodynamics and global (coronary sinus flow, CS F) as well as regional (great cardiac vein flow, GCVF) myocardial bloo d flow and metabolic variables were measured. During adenosine infusio n, in comparison to SNP, heart rate was unchanged, stroke volume index and cardiac index increased (24% and 32%, respectively), and the syst emic vascular resistance index decreased (-26%). Mean pulmonary arteri al pressure (24%) as well as pulmonary capillary wedge pressure (27%) and central venous pressure (18%) were higher with adenosine compared to SNP. Adenosine also increased CSF and GCVF (108% and 103%, respecti vely) without altering the CSF/GCVF flow ratio compared to SNP. Furthe rmore, adenosine increased the coronary oxygen content (51%) and decre ased the arterio-great cardiac vein oxygen content difference (-48%) w ithout changing regional myocardial oxygen consumption, indicating a m ore pronounced hyperkinetic myocardial circulation compared to SNP. In addition, adenosine infusion decreased arterial PO2 (-11%) and increa sed the intrapulmonary shunt fraction (57%). The PR interval time of t he electrocardiogram was prolongated (12%) and the ST segment was more depressed during adenosine infusion compared to SNP. Neither regional myocardial lactate extraction nor regional myocardial lactate uptake was altered during adenosine administration compared to SNP infusion. In one patient, adenosine induced myocardial ischemia compared to SNP. We conclude that adenosine induces a more pronounced systemic and cor onary vasodilation with higher cardiac index, stroke volume index, and myocardial blood flow when used to control postcardiac surgical hyper tension compared to SNP.