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.