Ultrasound assessment of extravascular lung water after thoracic surgery

Abstract

Introduction: Extravascular lung water (EVLW) increases following thoracic surgery because of altered fluid dynamics and vascular permeability. It may lead to alveolar-interstitial syndrome (AIS) that impairs gas exchange. AIS diagnosis is achieved by B-Lines and their absolute number is correlated with EVLW. Aims and Objectives: Aim of this prospective cohort study was to investigate by lung ultrasonography (LUS) the variation in EVLW following major pulmonary resection. Methods: EVLW was assessed at baseline and on postoperative days 1 and 4, using a 3,5 MHz convex probe, with patients undergoing lobectomy or pneumonectomy being examined in the sitting position. 4 sub-regions were identified in the inviolate hemithorax and B-lines were quantified according to a four-level scale analyzed jointly using a proportional odds model for repeated measures with baseline values as covariates. The respiratory ratio PaO2/FiO2 and fluid retention by measuring brain natriuretic peptide (BNP) were also assessed. Results: 48 men and 26 women underwent 64 lobectomies and 10 pneumonectomies; mean age 64. At baseline no patient showed AIS and the mean BNP value was normal. At extubation a significant inverse correlation was found between B-lines and the PaO2/FiO2 (OR-0.72; 95% CI 0.55-0.92; p=0.0096). There was a significant peak of B-lines on postoperative day 1, as well as a significant positiveassociation between B-lines and BNP (OR-1.00537; 95%CI 1.00295-1.00779; p Conclusions: Following major thoracic surgery LUS is able to estimate EVLW increase. The B-lines value is correlated to BNP and provides reliable information on the presence of AIS before it becomes clinically evident.