953-36 L-Arginine Administration Improves Left Ventricular Performance in Neonatal Lambs Following Cardiopulmonary Bypass and Two Hours of Global Hypothermic Ischemia

Abstract

Prior studies in isolated neonatal lamb hearts showed that the nitric oxide precursor L-Arginine (L-ARG), infused during reperfusion (rep) improved left ventricular (LV) function and coronary blood flow (CBF) after hypothermic ischemia. We evaluated the effects of L-ARG in an in situmodel of cardiopulmonary bypass (CPS) and hypothermic circulatory arrest (HCA) in 13 neonatal lambs with LV micromanometers and LV free wall sonomicrometry crystals. Before CPB, hemodynamics and LV regional preload recruitable stroke work (RPRSW) were recorded. Coronary blood flow (CBF) was determined with microspheres. Animals were cooled to 15°C prior to 2 hrs HCA. Group LARG (n = 6) received an infusion of L-ARG calculated to achieve a plasma concentration of 3 mM during the first 15 min of rep on CPS. Group CON (n = 7) received 0.2 mg/kg phentolamine at rep, according to the clinical protocol of this institution. Animals were weaned from CPB and data obtained for 3 hrs. No intergroup differences were seen in heart rate, systemic vascular resistance, cardiac output, or left atrial pressure at baseline or during rep. (p > 005) CBF at 1 and 2 hrs rep was not different between the two groups (p > 0.05). Rep RPRSW data are expressed as mean % recovery of baseline.Group1 hr2 hrs3 hrsCON65.563.552L-ARG80*81.7*84**p < 0.05 p < 0.05 Increased nitric oxide production during early rep improves recovery of the immature myocardium following CPS and HCA. Techniques such as this may have application in clinical cardiac surgery.