Lung ultrasound for the assessment of lung recruitment in pediatric patients during laparoscopic surgery. A randomized, controlled trial. 

Background: Atelectasis is a negative side effect of general anesthesia (GA) in pediatric patients. Such atelectasis not only reduces lung compliance but also impairs arterial oxygenation and predisposes to a ventilator-induced lung injury. Lung ultrasound (LUS) is a non- invasive reliable tool to detect anesthesia-induced atelectasis in pediatric patients. The aim of this study was to compare lung aeration between two different mechanical ventilation strategies (protective mechanical ventilation vs recruitment maneuvers) in pediatric patients scheduled for abdominal laparoscopic surgery using ultrasound imaging. 
Materials and methods: Forty-two patients ASA I-II, aged 6 months-7yr were included, randomized to either a protective mechanical ventilation group (PV-g), (TV 6ml/kg, respiratory rate according with the age of the patients, FiO2 0.5 and PEEP 5cmH2O) or recruitment maneuver group (RM-g); RM was done before capnoperitoneum followed by the same ventilatory setting than the PV-g but this time using 8 cmH2O of PEEP.
LUS examinations were performed with a linear 6-12MHz probe at three time-points: T1: after anesthesia induction and before capnoperitoneum, T2: after capnoperitoneum and T3: at the end of surgery. An aeration score with a four-point-aeration (0=normal lung, 1=moderate aeration loss, 2=severe aeration loss, 3=complete aeration loss and consolidation) was calculated from LUS images. 
Results and discussion: Forty-two patients (36 men / 6 women) aged 46.21±2 months, weighing 18.54±6.7 kg were successfully study. Lung aeration at T1 was decreased in both groups: RM-g: 5.95±4.13 vs VP-g: 5.19±3.33 (p=0.51). (Figure 1) However, the RM group resulted in a lower aeration score compared with PV group at both T2 and T3: 2.71±2.47 vs 6.71±3.54 (p<0.001) and 2.52±2.86 vs 8.48±3.22 (p<0.001), respectively (Figure 2). Lung compliance and oxygenation were significantly improvement in RM-g compared to PV-g at T2 20.7±9.2 vs 16.7±4.8 (p=0.083) and 98.9±0.6 vs 98.33.7±0.7 (p=0.009) and T3 28.4±10.3 vs 19.9±5.1 (p<0.001) and 99.2±0.7 vs 98.0±0.6 (p<0.001) respectively. 
Conclusion: In children scheduled for laparoscopic surgery, LUS can help anesthesiologists to detect those patients with atelectasis and to assess the response of a particular ventilatory setting. A RM followed by an individualized PEEP improved lung aeration score, respiratory compliance and arterial oxygenation compared with patients who received protective ventilation without lung recruitment.