USE OF AN ADJUSTABLE TOURNIQUET TO REVERSE CYANOSIS IN THE NEWBORN PIG

Background. previous surgical models of cyanosis have been permanent. Because normal oxygenation was not restored in these models, it is unc lear whether the metabolic changes produced by prolonged exposure to h yperemia are irreversible. We therefore designed an experimental model of cyanosis that is reversible.Methods. The left atrial appendage was anastomosed directly to the main pulmonary artery in 8 piglets, aged 2 to 4 weeks. Results. The oxygen saturation fell from 95.3% +/- 0.8% to 72.4% +/- 3.9% (p < 0.001). A tourniquet was placed around the anas tomosis to produce incremental changes in the level of cyanosis. Compl ete tourniquet occlusion resulted in obliteration of the right to left shunt, with return of systemic oxygen saturation to baseline levels. Systemic, left atrial, and pulmonary pressures did not change during t he study. Conclusions. In this acute preparation, stable hemodynamic c onditions were maintained despite substantial variations in systemic l evels of oxygenation. Most important, this model allows reversal of cy anosis with the return of normal oxygenation. Application of this expe rimental design in a chronic model may help to determine whether the m etabolic effects of prolonged hypoxemia are potentially reversible. (C ) 1997 by The Society of Thoracic Surgeons.