Pulmonary Ultrasound for the Assessment of Atelectasis in Anesthetized Children Using a Laryngeal Mask Airway.

Pulmonary Ultrasound for the Assessment of Atelectasis in Anesthetized Children Using a Laryngeal Mask Airway: a Randomized Double-Blinded Controlled Trial That Compares Spontaneous and Pressure Support Ventilation

This study will use lung ultrasounds (LUS) to evaluate the incidence and severity of intraoperative atelectasis in anesthetized children undergoing minor surgery using a laryngeal mask airway. The children will be randomly assigned to be left in spontaneous ventilation with a Positive End Expiratory Pressure (PEEP) of 5cmH2O or to be ventilated with a pressure support mode.

It is well known and described the deleterious effect that general anesthesia (GA) has on functional residual capacity (FRC), especially in children. This population is at higher risk of decreasing FRC during GA because of their lower capacity for elastic retraction and lower relaxation volume comparing to adults, predisposing them to the development of atelectasis and airway closure. These factors will lead to intrapulmonary shunts, which may impair the gas exchange and consequently oxygenation. By reducing the intrapulmonary shunt, Positive End Expiratory Pressure (PEEP) during controlled mechanical ventilation in patients with healthy lungs optimizes the FRC. However, the available data for an optimal ventilation strategy, including optimal PEEP, using a laryngeal mask airway (LMA) in the pediatric population are scarce, even though this device is frequently used in all age groups for brief general anesthesia.

Diagnosing anesthesia-induced atelectasis in the perioperative period can be possible by using lung ultrasounds (LUS), a simple, easily accessible, non-invasive and radiation free technique, which might help determine the impact in pulmonary aeration between different ventilation strategies. In our study, we will focus on comparing spontaneous ventilation (VS) with a PEEP of 5 cmH2O and pressure-support ventilation using a LMA in anesthetized children undergoing minor and elective outpatient surgery.

Inclusion Criteria:

• fasted children between 12 months and 8 years of age; American Society of Anesthesiology (ASA) score I or II without lung disease; baseline pulse oximetry in room air >96%; scheduled for minor urological surgery (circumcision) under general anesthesia; written parent's agreement.

Exclusion Criteria:

• ASA score > II, chronic lung disease, airway infection in the last 15 days, impossibility of insertion of LMA.