EFFICACY OF INHALED NITRIC-OXIDE IN PATIENTS WITH SEVERE ARDS

Study objective: To investigate the initial and long-term effect of ni tric oxide (NO) inhalation in patients with severe acute respiratory d istress syndrome (ARDS). Design: Retrospective, clinical study. Settin g: University surgical ICU. Patients: Eighty-seven patients with sever e ARDS. Interventions and measurements: Thirty of 87 patients with ARD S inhaled low concentrations of NO for more than 48 h in addition to t he standard treatment. Initial and long-term effects of NO inhalation on hemodynamics, gas exchange, and methemoglobin formation were determ ined. Survival of patients treated with inhaled NO was compared with s urvival in similar patients without NO inhalation. Results: In 83% of the patients, NO increased the ratio of arterial Po-2 to the fraction of inspired O-2 (PaO2/FIo(2)) by greater than or equal to 10 mm Hg; in 87%, NO reduced venous admixture (QVA/QT) by greater than or equal to 10%, and in 63%, NO decreased mean pulmonary artery pressure (PAP) by greater than or equal to 3 mm Hg. Daily short interruption of continu ous inhalation of NO for a duration of 17+/-2.4 days was consistently associated with a decrease in PaO2/FIo(2) by 81+/-4 mm Hg (p<0.001). Q VA/QT increased by 8.3+/-0.4% (p<0.001) and PAP by 5.3+/-0.3 mm Hg (p< 0.001). Over time, we observed neither tachyphylaxis nor a more pronou nced effect of inhaled NO. Methemoglobin increased from 0.74+/-0.56% t o 0.98+/-0.02% (p<0.001). Survival rates in patients treated with NO d id not differ from survival rates in patients not treated with NO. Con clusion: Beneficial effects of NO inhalation can be observed in most p atients with severe ARDS; in some cases,however, it may fail to improv e pulmonary gas exchange or to reduce pulmonary hypertension without o bvious explanation. To demonstrate a possible increase in survival ass ociated with NO inhalation, large randomized prospective trials are re quired.