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 unclear whether the metabolic changes produced by prolonged exposure to hypoxemia 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 anastomosis to produce incremental changes in the level of cyanosis. Complete 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 the study. Conclusions. In this acute preparation, stable hemodynamic conditions were maintained despite substantial variations in systemic levels of oxygenation. Most important, this model allows reversal of cyanosis with the return of normal oxygenation. Application of this experimental design in a chronic model may help to determine whether the metabolic effects of prolonged hypoxemia are potentially reversible. (Ann Thorac Surg 1997;63:456–8)