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[Inhaled nitrous oxide (NO) for the treatment of ARDS]
M C Olivei1, A Palo, C Galbusera
1Laboratorio di Biotecnologie e Tecnologie Biomediche, IRCCS Policlinico S. Matteo, Pavia.
Objective:
To investigate the initial longterm effect of inhaled NO on hypoxemia in ARDS patients.
Design:
Retrospective study.
Patients:
Nine hypoxemic patients with ARDS (Murray Lung Injury Score, LIS, 2.8 +/- 0.3), treated with conventional mechanical ventilation.
Interventions:
Continuous NO inhalation was started after a test of inhaled NO efficacy on gas exchange and hemodynamics. Long term effects of inhaled NO were evaluated daily in terms of arterial oxygenation and methemoglobin formation.
Results:
The initial NO inhalation increased the PaO2/FiO2 from 141 +/- 64 mmHg to 216 +/- 70 mmHg (p < 0.0001) and decreased the mean pulmonary pressure from 38 +/- 7 mmHg to 32 +/- 5 mmHg (p < 0.01), the pulmonary venous admixture from 29 +/- 10% to 20 +/- 8% (p < 0.01) and the pulmonary vascular resistance from 325 +/- 97 dyne.s.cm-5 to 238 +/- 48 dyne.s.cm-5 (p < 0.01). Daily withdrawal of inhaled NO, which was administered for 14 +/- 16 days at 8 +/- 2 ppm, was associated with a decrease in PaO2/FiO2 by 61 +/- 32 mmHg (p < 0.0001). During prolonged NO inhalation the FiO2 was decreased, on average, by 0.34 +/- 0.19 (p < 0.01), the positive end-expiratory pressure by 4 +/- 2 cmH2O (p < 0.01) and the peak inspiratory pressure by 7 +/- 4 cmH2O (p < 0.01). Three patients died during the ICU stay.
Conclusions:
Our results confirm the interest for inhaled NO as an additional approach for the treatment of hypoxemia in ARDS. Inhaled NO seems to allow for a better control of gas exchange, rather than for a rapid reduction of the ventilatory support.