Acute effects of inhaled nitric oxide in adult respiratory distress syndrome

Abstract

In patients with adult respiratory distress syndrome (ARDS), inhaled nitric oxide (NO) may both reduce pulmonary hypertension and improve arterial oxygenation [1,2]. The NO-induced decrease in pulmonary artery pressure depends on the selective pulmonary vasodilating effect of inhaled NO [3], while the NO-induced increase in arterial oxygenation is related to the redistribution of pulmonary blood flow to well-ventilated lung areas, which results in improved ventilation to perfusion matching [1,4]. Although potentially beneficial, inhaled NO is a toxic compound, and its toxicity is increased by the oxidation of NO to NO 2 , which occurs during administration of inhaled NO, especially when the inhaled oxygen concentration is high [5]. In order to minimize the risks of toxicity, inhaled NO should be administered at the lowest effective concentration to achieve maximal therapeutic effects [6,7].There is conflicting information on the NO dose for optimal treatment of pulmonary hypertension and hypoxaemia in ARDS. It has been shown that very low NO doses (<1 parts per million (ppm)) may have a measurable effect both on pulmonary circulation and on arterial oxygenation in ARDS patients [8][9][10]. Published data indicate that low NO doses, between 1-5 ppm, achieve maximal haemodynamic and oxygenation responses [9][10][11][12]. However, other studies in ARDS patients indicate that higher NO doses may induce an additional reduction in pulmonary hypertension and hypoxaemia. In a study by GERLACH et al. [13], a dose of NO as high as 100 ppm was required to achieve maximal pulmonary vasodilation, while the impro-vement in arterial oxygen tension (Pa,O 2 ) was maximal at 1 ppm. In contrast, a study on septic ARDS patients rep-orted a dose-dependent increase in Pa,O 2 in the range 0.1-150 ppm and a plateau effect in pulmonary pressure at 5 ppm [14]. A recent study showed that the optimum NO dose to improve Pa,O 2 may vary widely between individuals, ranging 0.1-100 ppm [15]. In that same study, however, the effect on pulmonary haemodynamics was negligible.The aim of this study was to evaluate the dose-response effect of inhaled NO (0.5-100 ppm) on gas exchange and haemodynamics in ARDS patients treated with conventional mechanical ventilation. Materials and methods PatientsDuring a 10-month period, 19 consecutive patients who were mechanically ventilated for severe ARDS were screen- Olivei, A. Palo, C. Galbusera, R. Veronesi, A. Braschi. ©ERS Journals Ltd 1998. ABSTRACT: This study evaluated the dose-response effect of inhaled nitric oxide (NO) on gas exchange, haemodynamics, and respiratory mechanics in patients with adult respiratory distress syndrome (ARDS). Acute effects of inhaled nitric oxide in adult respiratory distress syndrome. G.A. Iotti, M.C.Of 19 consecutive ARDS patients on mechanical ventilation, eight (42%) responded to a test of 10 parts per million (ppm) NO inhalation with a 25% increase in arterial oxygen tension (Pa,O 2 ) over the baseline value. The eight NO-responders were extensively studied during admin...

Effect of inhaled nitric oxide in combination with almitrine on ventilation-perfusion distributions in experimental lung injury

“…Regarding MPAP, we observed only a small, although significant decrease, which may be due to individual differences in the response to the single dose of 10 ppm NO used in our investigation. In clinical routine, a dose-response study is usually performed prior to the treatment with inhaled NO to reveal the dose with the best impact on gas exchange and pulmonary artery pressure [25,26,27,28]. Intravascular NO is known to be rapidly bound to Hb, which is transformed to MetHb in the presence of oxygen.…”

Uso do óxido nítrico em pediatria

“…Doses of iNO much greater than those used clinically do not cause significant methemoglobinemia in adults. 58 In work we have published we did not observe methemoglobin above 2% of total hemoglobin.…”

“…Abman et al, in 1994, 34 described beneficial effects on oxygenation, PH and cardiac index in children with the syndrome. Later, studies conducted on adults 35,36 and children, 37,38 while confirming the immediate beneficial effects, were not capable of demonstrating a prolonged response to iNO therapy. Dobyns et al, 39 however, observed a prolonged response to iNO as compared to therapy with a placebo in subgroups of patients; those with the most serious respiratory failure (oxygenation index > 25) and among immunodepressed patients.…”

Inhaled nitric oxide in pediatrics

“…Abman et al, em 1994 34 , descreveram efeitos benéficos do gás sobre a oxigenação, HP e índice cardíaco em crianças com a síndrome. Posteriormente, estudos conduzidos em adultos 35,36 e em crianças 37,38 , enquanto confirmaram os efeitos benéficos imediatos, não foram capazes de demonstrar resposta prolongada da terapia com NOi. No entanto, Dobyns et al 39 observaram resposta prolongada ao NOi versus terapia com placebo em subgrupos de pacientes, aqueles com insuficiência respiratória mais grave (índice de oxigenação > 25) e nos pacientes imunodeprimidos.…”

“…Níveis acima de 2% do total de hemoglobina podem prejudicar a liberação do oxigênio e piorar a hipóxia tecidual. Doses de NOi muito maiores do que aquelas usadas clinicamente não causam metemoglobinemia significante em adultos 58 . Nos trabalhos que publicamos não observamos metemoglobina acima de 2% do total de hemoglobina.…”