The Effect of Vasodilatation on Metabolic and Hemodynamic Parameters During and After Cardiopulmonary Bypass

Abstract

The effects of active vasodilatation with an infusion of trimetha-phan camphorsulfonate (2.3 +0.9 mg/kg) were studied in 4 dogs undergoing hypothermic (32[degree]C), constant flow (2.35 1/mVmincardiopulmon-ary bypass for 60 min. Four control dogs were treated identically, but were not actively vasodilated. Despite identical O2 consumption and PaC02 values, the treated animals showed a greater metabolic acidosis at the end of bypass. When compared to control animals, the treated group demonstrated a greater O2 consumption (115-119%, P < 0.05) and difference in arterio-venous O2 content (154-173%, P < 0.001); with a lesser cardiac index (70-75%, P < 0.01) during the post-bypass period (180 min.). This was accompanied by a greater urinary output and a more rapid correction of metabolic acidosis. However, the actively vasodilated animals showed grossly abnormal pulmonary ventilation-perfusion ratios (compared to control animals) as demonstrated by lower PaQ2 values (21-29%, P < 0.001) and higher PaCO2 values (142-187%, P < 0.05). This relative CO2 retention resulted in a consistently lower arterial pH despite the tendency towards correction of metabolic defects.