Background: The goal of this study was to examine the effects of coadministration of sildenafil and inhaled nitric oxide (iNO) in patients with out-of-proportion pulmonary hypertension who underwent cardiac valve replacement surgery.
Methods and results: Twenty consecutive cardiac surgery patients with out-of-proportion pulmonary hypertension were randomly assigned postoperatively into 2 groups: group A received 10 ppm of iNO followed by sildenafil (100 mg) orally 30 minutes later, and group B initially received sildenafil (100 mg) orally followed by 10 ppm of iNO 60 minutes later. Hemodynamic and gas exchange data were obtained at baseline, after administration of either iNO or sildenafil alone, and at 90 minutes from baseline. In group A, iNO resulted in a significant reduction in mean pulmonary artery pressure (MPAP) and pulmonary vascular resistance index (PVRI) (by 9.6% and 20.8%, respectively). In group B, sildenafil administration also resulted in a significant decrease in mean arterial pressure, MPAP, pulmonary artery occlusive pressure, PVRI, and systemic vascular resistance index but also in the PaO(2)/inspired fraction of oxygen ratio (by 18.7%, 22.0%, 15.7%, 31.6%, 21.3%, and 14%, respectively). In both groups, the coadministration of the 2 drugs resulted in a significant further reduction of mean arterial pressure, MPAP, pulmonary artery occlusive pressure, systemic vascular resistance index, and PVRI, whereas cardiac index and mixed venous oxygen saturation remained unchanged. The hypoxemia after sildenafil administration in group B improved after the coadministration of iNO, and thus PaO(2)/inspired fraction of oxygen returned to values near baseline.
Conclusion: In this study, the postoperative coadministration of iNO and oral sildenafil in patients with out-of-proportion pulmonary hypertension undergoing cardiac surgery is safe and results in an additive favorable effect on pulmonary arterial pressure and pulmonary vascular resistance, without systemic hypotension and ventilation/perfusion mismatch.