Influence of nimodipine and nifedipine on intrapulmonary shunting--a comparison to other vasoactive drugs.

This study was assigned to investigate the influence of calcium channel blockers (nimodipine and nifedipine) in comparison to other vasoactive drugs (nitroglycerin, dopamine) on pulmonary shunting (Qs/Qt). Fifty anesthetised patients scheduled for aortocoronary bypass operation were randomly allocated to 5 groups receiving one of the following drugs: nimodipine 1.0 microgram X kg-1 X min-1; nifedipine 0.7 microgram X kg-1 X min-1; nitroglycerin (TNG) 0.5 microgram X kg-1 X min-1; dopamine; micrograms X kg-1 X min-1; placebo (0.9% NaCl). Nimodipine as well as nifedipine led to a significant increase in cardiac output (+44%; +39%), pulmonary vascular resistance simultaneously decreased (-25%; -28%). PaO2 increased significantly (+16%; +13%), too, whereas Qs/Qt remained almost unchanged. In contrast, the increase in cardiac output induced by dopamine (+27%) was accompanied by a significant increase in shunting (+34%). TNG application did not alter Qs/Qt, but pulmonary artery pressure (PAP) decreased markedly (-19%).