Short-term effects of neuromuscular blockade on global and regional lung mechanics, oxygenation and ventilation in pediatric acute hypoxemic respiratory failure

BACKGROUND: Neuromuscular blockade (NMB) has been shown to improve outcome in acute respiratory distress syndrome (ARDS) in adults, challenging maintaining spontaneous breathing when there is severe lung injury. We tested in a prospective physiological study the hypothesis that continuous administration of NMB agents in mechanically ventilated children with severe acute hypoxemic respiratory failure (AHRF) improves the oxygenation index without a redistribution of tidal volume V (T) toward non-dependent lung zones. METHODS: Oxygenation index, PaO(2)/FiO(2) ratio, lung mechanics (plateau pressure, mean airway pressure, respiratory system compliance and resistance), hemodynamics (heart rate, central venous and arterial blood pressures), oxygenation [oxygenation index (OI), PaO(2)/FiO(2) and SpO(2)/FiO(2)], ventilation (physiological dead space-to-V (T) ratio) and electrical impedance tomography measured changes in end-expiratory lung volume (EELV), and V (T) distribution was measured before and 15 min after the start of continuous infusion of rocuronium 1 mg/kg. Patients were ventilated in a time-cycled, pressure-limited mode with pre-set V (T). All ventilator settings were not changed during the study. RESULTS: Twenty-two patients were studied (N = 18 met the criteria for pediatric ARDS). Median age (25–75 interquartile range) was 15 (7.8–77.5) weeks. Pulmonary pathology was present in 77.3%. The median lung injury score was 9 (8–10). The overall median CoV and regional lung filling characteristics were not affected by NMB, indicating no ventilation shift toward the non-dependent lung zones. Regional analysis showed a homogeneous time course of lung inflation during inspiration, indicating no tendency to atelectasis after the introduction of NMB. NMB decreased the mean airway pressure (p = 0.039) and OI (p = 0.039) in all patients. There were no significant changes in lung mechanics, hemodynamics and EELV. Subgroup analysis showed that OI decreased (p = 0.01) and PaO(2)/FiO(2) increased (p = 0.02) in patients with moderate or severe PARDS. CONCLUSIONS: NMB resulted in an improved oxygenation index in pediatric patients with AHRF. Distribution of V (T) and regional lung filling characteristics were not affected.