Aj. Betbese et al., HEMODYNAMIC AND GAS-EXCHANGE EFFECTS OF N ITRIC-OXIDE INHALATION IN PATIENTS WITH ACUTE RESPIRATORY-DISTRESS SYNDROME, Medicina Clinica, 107(6), 1996, pp. 201-206
BACKGROUND: To analyze the effects on gas exchange and hemodynamics of
nitric oxide inhalation in patients with acute respiratory distress s
yndrome. PATIENTS AND METHODS: Prospective study including 16 acute re
spiratory distress syndrome patients, We analyzed the acute and short-
term (5 days) effects of inhaling 5 parts per million (ppm) nitric oxi
de on gas exchange and hemodynamics. RESULTS: After nitric oxide inhal
ation, PaO2/FiO(2) ratio changed from 81 +/- 25 to 126 +/- 57 mmHg (p
= 0.0001), mean pulmonary artery pressure decreased from 30.1 +/- 8.2
to 27.3 +/- 6.6 mmHg (p = 0.002), intrapulmonary shunt decreased from
44.6 +/- 11% to 34.1 +/- 7.9% (p = 0.002) and cardiac index did not ch
ange. Thirteen out of 16 patients (81.2%) presented at least a 20% imp
rovement in PaO2/FiO(2) ratio, In the 10 patients treated over 5 conse
cutive days, we observed that those who improved (increase in PaO2/FiO
(2) ratio higher than 20% after inhaling 5 ppm nitric oxide) showed a
lower cardiac index, a higher mean pulmonary artery pressure and a hig
her pulmonary vascular resistance index than those who did not: Cl 3.9
+/- 0.81 vs 4.9 +/- 0.81 l/min/m(2) (p < 0.001), mean pulmonary arter
y pressure 32.4 +/- 7 vs 25.3 +/- 4.2 mmHg (p = 0.001), and pulmonary
vascular resistance index 421 +/- 199 vs 241 +/- 106 dyn.s.cm(-5)/m(2)
(p = 0.003). Mean levels of methemoglobin were 1.1 +/- 0.24% (range:
0.4-1.6%), and NO2 concentration was always lower than 100 parts per b
illion. CONCLUSIONS: Low doses of inhaled nitric oxide induce a select
ive pulmonary vasodilatation and significant improvement of oxygenatio
n in the majority of acute respiratory distress syndrome patients, alt
hough those with a hyperkinetic hemodynamic status are less likely to
improve the oxygenation. These effects are maintained for at least 5 d
ays. We did not observe rebound effects.