NOREPINEPHRINE INFUSION FOLLOWING CARDIOPULMONARY BYPASS - EFFECT OF INFUSION SITE

The placement of left atrial catheters following cardiopulmonary bypas s (CPB) allows accurate monitoring of left ventricular filling pressur es, as well as access for the infusion of vasoactive drugs. While the left atrial administration of norepinephrine (NE) is thought to provid e higher systemic arterial NE levels while minimizing any pulmonary va soconstriction, no study critically compares central venous and left a trial NE infusion following cardiopulmonary bypass. A canine model was used to compare central venous and left atrial NE infusion at three d osages (0.2, 0.4, and 0.6 mu g/kg/min) both prior to CPB and following 2 hr of hypothermic CPB at 27 degrees C. Prior to CPB, there was no d ifference in the hemodynamic efficacy of central venous and left atria l NE infusion at any dosage. The pulmonary circulation metabolized 16- 29% of circulating NE. Only at the 0.2 mu g/kg/min dose was there a di fference in the arterial NE level between central venous (3474 +/- 486 pg/ml) and left atrial (5504 +/- 751 pg/ml, P = 0.019) NE administrat ion. Above this dose, no difference in the arterial NE level was ident ified. Following 2 hr of CPB, the pulmonary endothelium metabolized a significantly higher percentage of circulating NE (35-42%). Despite th is increased extent of pulmonary metabolism, there was no difference i n the hemodynamic efficacy or the resulting arterial NE level of centr al venous and left atrial NE infusion at a given dose. In conclusion, the results demonstrate: (1) increased pulmonary NE uptake following C PB, and (2) no difference in hemodynamic efficacy between central veno us and left atrial NE infusion over a wide range of three doses in a m odel with normal lungs. (C) 1995 Academic Press, Inc.