Evaluation of atelectasis using electrical impedance tomography during procedural deep sedation for MRI in small children: A prospective observational trial

Study objective: To investigate the variation of poorly ventilated lung units (i.e., silent spaces) in children undergoing procedural sedation in a day-hospital setting, until discharge home from the Post-Anesthesia Care Unit (PACU).

Design: Prospective, single-center, observational cohort trial.

Setting: This study was conducted at the radiology department and in PACU at Bern University Hospital (Switzerland), a tertiary care hospital.

Patients: We included 25 children (1-6 years, ASA I-III) scheduled for cerebral magnetic resonance imaging scan, spontaneously breathing under deep sedation. Children planned for tracheal intubation, supraglottic airway insertion, or with contraindication for propofol were excluded.

Intervention: After intravenous or inhaled induction, deep sedation was performed with 10 mg/kg/h Propofol. All children received nasal oxygen 0.3 ml/kg/min.

Measurements: The proportion of silent spaces and the global inhomogeneity index were determined at each of five procedural points, using electrical impedance tomography: before induction (T1); before (T2) and after (T3) magnetic resonance imaging; at the end of sedation before transport to the PACU (T4); and before hospital discharge (T5).

Main results: The median [interquartile range (IQR)] proportion of silent spaces at the five analysis points were: T1, 5% [2%-14%]; T2, 10% [7%-14%]; T3, 12% [5%-23%]; T4, 12% [7%-24%]; and T5, 3% [2%-11%]. These defined significant changes in silent spaces over the course of sedation (p = 0.009), but no differences in silent spaces from before induction to before discharge from the PACU (T1 vs. T5; p = 0.29). Median [IQR] global inhomogeneity indices were 0.57 [0.55-0.58], 0.56 [0.53-0.59], 0.56 [0.54-0.59], 0.57 [0.54-0.60] and 0.56 [0.54-0.57], respectively (p = 0.93). None of the children reported anesthesia-related complications.

Conclusion: Deep sedation results in significantly increased poorly ventilated lung units during sedation. However, this does not significantly affect ventilation homogeneity, which was fully resolved at discharge from the PACU.

Trial registration: clinicaltrials.gov, identifier NCT04507581.