Lung ultrasound (LUS) for the assessment of extravascular lung water (EVLW) and effect on oxygenation in cardiac surgery: a prospective study

Abstract

Introduction EVLW accumulates in the interstitial and alveolar space and represented by vertical artifacts known as B-lines using LUS1. Excess lung water causes poor oxygenation and prolonged ventilation. Aim: To score B-lines using LUS to assess EVLW pre- and post-cardiac surgery and record the effect on oxygenation and time of extubation (Extub T). Methods A prospective cohort study in cardiac surgery using cardiopulmonary bypass (CPB). King Abdullah International Medical Research Center approved this study reference: RYD-18-417780-17652. LUS was performed: pre- T0, one-hour T1 and 24 hrs T2 post-surgery. The arterial oxygen partial pressure to inspired oxygen (PaO2/FiO2) ratio was recorded at each time. LUS was performed using a Philips CX50 and phased array probe, with LUS preset. Ten anatomical sites- thoracic left and right- anterior, lateral and posterior were assessed by LUS and scored according to the number of B-lines. Fluid balance at T1 and T2 was recorded. 79 patients were recruited using consecutive sampling (March 2018 to March 2019). SPSS v23, with simple descriptive and Pearson correlation analysis reported. Significance of p Results 73 patients completed the study age 56 (18-87 years). We found a negative correlation between LUS score and PaO2/FiO2 at T1 p There was a positive correlation with changes in LUS score at T1 and Extub T p Also a positive correlation between LUS score at T2 and a positive fluid balance p Discussion We showed a negative correlation between ultrasound signs of EVLW and oxygenation. The fewer B-lines the better the oxygenation. The more B-lines the longer the period of ventilation. This is in agreement with other LUS studies identifying patients with increased EVLW by B-lines and a decreased of PaO2/FiO2 correctable by dialysis2.