Monitoring atelectasis and tidal recruitment using lung ultrasound in an anesthetized child. A case report 

Acosta C.M.1, Tusman G.1, Costantini M.1,  Alvarez J.1, Carpinela M.1, Echevarria C.2
Department of Anesthesia1, Department of Radiology2, Hospital Privado de Comunidad, Mar del Plata, Buenos Aires, Argentina.

Background: Lung ultrasound (LUS) is an accurate, safe and non-invasive method for diagnosing atelectasis and tidal recruitment (TR), conduct lung recruitment maneuvers and individualize positive end-expiratory pressure (PEEP). 
Case report: A 4-year-old ASA I anesthetized child scheduled for laparoscopic surgery, protective ventilation was applied using volume controlled ventilation (tidal volumen: 6 ml/kg, respiratory rate 25, I:E ratio 1:1.5, PEEP 5 cmH2O and FIO2 0.5. Immediately after anesthesia induction the patient showed plateau pressure of 24 cmH2O and SpO2 of 95%. LUS was performed with a linear HF probe (6-12MHz) showing atelectasis and TR in dependent, para-diaphragmatic lung areas. Most of the atelectatic area observed at end expiration disappeared at the end of the next inspiration (i.e it was tidally recruited). Lung recruitment maneuver - a brief and controlled step-wise increment in airways pressure to re-expands atelectasis - was performed. LUS images showed resolution of atelectasis during such maneuver. Later on, a protective ventilation pattern was reassumed but this time with PEEP 9 cmH2O to maintain the lungs free of atelectasis. This ventilatory pattern resulted in a plateau pressure 18 cmH2O, SpO2 100% (FIO2 0.3) and without the presence of atelectasis nor TR in LUS images.
Discussion: Point-of-care LUS is a noninvasive method helpful to assess lung aeration.1 This tool was accurate for diagnosing anesthesia-induced atelectasis in children.2 Likewise the high time-resolution of LUS images is a key feature to detect TR within atelectasis, one of the proposed mechanisms of ventilator-induced lung injury (VILI). This case illustrates how the atelectatic area appeared as a LUS consolidation pattern that cyclically changes during breathing; confirming the presence of this mechanism of VILI in healthy lung ventilated with a lung protective setting. Moreover, the elimination of the consolidated lung area by means of a recruitment maneuver confirmed the elimination of the mechanism of TR. LUS can therefore become a valuable monitoring tool to prevent VILI at the bedside. 
Learning points: LUS could identify children with atelectasis and TR. Their resolution by lung recruitment together with an optimal setting of PEEP can be easily guided with LUS, helping anesthesiologists optimize ventilator strategy in operating rooms. 

References:
1-	Bouhemad B, et al. Anesthesiology 2015;122:437-47
2-	Acosta CM, et al. Anesthesiology 2014;120: 1370-9