Does lung ultrasound score predict the need for surfactant in extremely preterm neonates?

Abstract

Commentary on: De Martino L, Yousef N, Ben-Ammar R, et al. Lung Ultrasound Score Predicts Surfactant Need in Extremely Preterm Neonates. Pediatrics. 2018;142(3):e20180463. PMID 30108142. Respiratory distress syndrome (RDS) is almost universal in the extremely preterm neonate, and select patients benefit from timely administration of surfactant therapy 1. Use of lung ultrasonography to assign a semi-quantitative lung ultrasound score (LUS) may predict which neonates will require surfactant therapy 2. This was a prospective cohort diagnostic accuracy study to assess the ability of the LUS to predict the need for surfactant treatment and re-treatment in neonates ≤30 weeks’ gestational age with RDS on continuous positive airway pressure (CPAP). Patients had a lung ultrasound performed to assign a LUS, and then need for treatment and re-treatment with surfactant relied solely on the inspired fraction of oxygen (FiO2) requirement 3. We evaluated the study using the QUADAS-2 tool–see attached supplement 4. Patients were enrolled consecutively with appropriate inclusion/exclusion criteria. The study was well-powered. The index test was the LUS with no pre-specified thresholds. Of note, lung ultrasonography is the first-line imaging to evaluate RDS at this institution. The ultrasound operator was not blinded to the patient's FiO2 requirement, which increases the risk of bias, although previous studies demonstrated good inter-rater reliability under similar conditions 2. The physician was blinded to the LUS results, however, when determining the need for surfactant therapy based on the FiO2 reference standard. The authors report that a lung ultrasound was performed on average at 30 minutes of life, and that the first dose of surfactant was administered at a mean of four hours of life, but it is unclear how long the patient had to exceed the FiO2 requirement before a decision was made to treat. Receiver operating characteristic analysis demonstrated good predictive value with an area under the curve ≥0.9 across all gestational ages. It was closer to 0.8, however, when predicting the need for re-treatment. LUS cut-offs also predicted the need for treatment and re-treatment with surfactant. The authors did not provide clinical characteristics for patients requiring treatment or re-treatment versus no treatment, so it is unclear whether there were confounding factors. For example, only 60% of study patients received a full antenatal steroid course, but the authors did not report whether this varied between the treatment versus no treatment groups. The secondary outcome correlating LUS with oxygenation index demonstrated good agreement. Overall, the results support the reliability of the LUS to predict the need for surfactant treatment in this population. This study's primary limitation is applicability. While the authors used low FiO2 cut-offs (30% for ≤ 28 weeks and 40% for > 28 weeks) to administer surfactant, the FiO2 requirement constituting CPAP failure varies in the literature from 30-75% 1, 5, 6–restricting the applicability of these results to institutions which utilise similar thresholds. Additionally, although other studies report good reliability of the LUS 3, 7, 8, a recent systemic review by Hiles, et al., found only moderate quality evidence to support its use 9. Thus, more research is needed prior to universal implementation, so for now this study's results are limited to NICUs with similar expertise. https://ebneo.org/2019/01/lung-ultrasound-score/ None. None.