INHIBITION OF PLATELET-AGGREGATION BY INHALED NITRIC-OXIDE IN PATIENTS WITH ACUTE RESPIRATORY-DISTRESS SYNDROME

Background: Nitric oxide inhibits platelet adhesion and aggregation in vitro. The aim of this prospective study was to assess the platelet a ntiaggregating activity of nitric oxide administered to patients with acute respiratory distress syndrome CARDS) at increasing concentration s. Methods: In six critically ill patients (mean age 37 +/- 16 yr) wit h ARDS (lung injury severity score greater than or equal to 2.2), the lungs were mechanically ventilated with inhaled nitric oxide (1, 3, 10 , 30, and 100 ppm) randomly administered, Patients with cardiac dysrhy thmias, septic shock, an underlying hemostasis disorder (constitutive or acquired), a platelet count less than 100 Giga/l, or a decreased pl atelet aggregation and those treated with antiplatelet or anticoagulan t agents were excluded, Platelet aggregation was measured without nitr ic oxide and at each nitric oxide concentration in platelet-rich plasm a issued from radial artery. Ivy bleeding time using a horizontal inci sion was simultaneously performed. Results: After nitric oxide, a non- dose-dependent but statistically significant decrease in ex vivo plate let aggregation induced by three aggregating agents was observed: aden osine diphosphate = -56 +/- 18%, collagen = -37 +/- 18%, and ristoceti n = -45 +/- 18% Cp < 0.05), In each individual, Ivy bleeding time rema ined within normal values measured in healthy volunteers, and variatio ns after nitric oxide did not correlate with changes in platelet aggre gation. Simultaneously, arterial oxygenation improved significantly an d pulmonary artery pressure decreased significantly. Conclusions In pa tients with ARDS and without preexisting coagulation disorders, the be neficial effects of inhaled nitric oxide on arterial oxygenation and p ulmonary circulation are associated with a significant inhibition of p latelet aggregation, This antithrombotic effect is not associated with a significant prolongation of the bleeding time.