Background: The purpose of this study was to assess the hemodynamic effects of low doses of inhaled nitric oxide in patients after orthotopic heart transplantation.
Methods: Two hours after the operation 10 adult patients who were still under anesthetic effects and undergoing mechanical ventilation inhaled, during 60 minutes, a mixture of nitrogen, oxygen, and nitric oxide (20 ppm). A standard profile of hemodynamic data was collected at baseline, at 30 minutes, at 30 more minutes of inhalation, and at the same points after nitric oxide suspension.
Results: A significant decrease was found from baseline to 60 minutes, immediately after nitric oxide inhalation in the following: systemic vascular resistance index 1268 +/- 409 to 1090 +/- 354 (p = 0.0161); pulmonary vascular resistance index 252 +/- 124 to 154 +/- 98 (p < 0.05); pulmonary vascular resistance index/systemic vascular resistance index ratio 0.21 +/- 0.09 to 0.14 +/- 0.08 (p = 0.0025); transpulmonary gradient 12 +/- 3 to 9 +/- 3 (p = 0.05). A significant increase was also found in cardiac index from 4.2 +/- 1.1 to 4.9 +/- 1.4 (p = 0.0007). Other parameters such as mean pulmonary, systemic, wedge and right atrial pressures, in addition to intrapulmonary shunting, heart rate, and oxygen extraction ratio, did not present any significant changes. The procedure was well tolerated by all patients, and no undesirable effects such as methemoglobin elevation or worsening of pulmonary hypertension after nitric oxide suspension were observed.
Conclusions: The beneficial effects observed by inhaled nitric oxide in the pulmonary vascular resistance index/systemic vascular resistance index ratio, transpulmonary gradient, and cardiac index suggest that nitric oxide acts mainly in pulmonary territory and could be a possible pulmonary vasodilator agent used to control central hemodynamics after heart transplantation.