Effects of nitric oxide inhalation after pulmonary thromboendarterectomy for chronic pulmonary thromboembolism

STUDY OBJECTIVES: To examine the hypothesis that nitric oxide (NO) inhalation improves hemodynamics and gas exchange in patients with chronic pulmonary thromboembolism after pulmonary thromboendarterectomy. DESIGN: Prospective crossover clinical study. SETTING:: Surgical ICU in a national education and research hospital. PATIENTS:: Seven patients (mean age +/- SD, 54 +/- 11 years) who underwent elective pulmonary thromboendarterectomy for chronic pulmonary thromboembolism. INTERVENTIONS: Patients breathed 20 parts per million of NO gas for 30 min at 12-h intervals until extubation of the trachea. MEASUREMENTS AND RESULTS: Hemodynamics and arterial blood gas levels were analyzed before, during, and after NO inhalation. Waveform of pulmonary artery pressure (PAP) was evaluated using fractional pulse pressure (PPf): (systolic PAP - diastolic PAP)/mean PAP. After surgery, pulmonary vascular resistance decreased, PPf decreased, and cardiac index increased significantly. At the first trial, NO inhalation resulted in a slight improvement in arterial oxygen tension (from 173 +/- 33 to 196 +/- 44 mm Hg; p < 0.05), while hemodynamics did not change significantly. Twelve hours later, NO inhalation decreased pulmonary vascular resistance index (from 312 +/- 98 to 277 +/- 93 dyne.s. cm(-5)/m(2); p < 0.01), while the change in oxygenation was not significant. CONCLUSIONS: Immediately after pulmonary thromboendarterectomy for chronic pulmonary thromboembolism, NO inhalation improved oxygenation; at 12 h after surgery, NO inhalation resulted in decreased pulmonary vascular resistance, although both changes were small.