INFLUENCE OF HEMODYNAMICS ON THE PERFORMANCES OF INTRAVASCULAR GAS EXCHANGERS

Background. The intravascular gas exchanger is a lung assist device fo r augmentation of gas exchange in critically ill patients with severe acute respiratory failure. These patients often require inotropic supp ort therapy due to the cardiovascular instability that almost inevitab ly accompanies severe respiratory failure. Methods. We investigated th e interaction of vasoactive medication (dopamine, nitroglycerin, and n oradrenaline) with the gas exchange performances of the intravascular gas exchanger in a bovine experimental model. Results. Dopamine admini stration highly increased cardiac output, caval now rates, and diamete r of vena cava inferior. These effects resulted in a significant incre ase in oxygen transfer (baseline, 35 +/- 6 mL/min versus 153 +/- 27 mL /min at 20 mu g . kg(-1) . min(-1) of dopamine, p < 0.001) and carbon dioxide elimination (baseline, 35 +/- 2 mL/min versus 47 +/- 4 mL/min at 20 mu g . kg(-1) . min(-1) of dopamine, p < 0.001). Administration of nitroglycerin did not cause significant changes of the hemodynamic parameters nor did it affect the oxygen transfer or carbon dioxide eli mination. Noradrenaline caused a moderate increase in cardiac output a nd caval now, but no changes of caval diameter. Hemodynamic changes we re accompanied by an increase in oxygen transfer from 38 +/- 5 mL/min to 68 +/- 7 mL/min (p < 0.01) and carbon dioxide elimination from 33 /- 1 mL/min to 40 +/- 1 mL/min (p = 0.03). The multiple regression ana lysis showed significant influence of changes in cardiac output on oxy gen transfer (p < 0.001) and carbon dioxide elimination (p = 0.004). T he administration of vasoactive drugs induced slight changes in caval diameter that did not significantly affect the gas transfer. Conclusio ns. The results from our study reveal the major influence of cardiac o utput on efficiency of gas transfer of the intravascular oxygenator.