The Correlation between B - lines Scores and Mean Pulmonary Artery Pressure in Post - Cardiac Surgical Patients

Abstract

Background: Mean pulmonary artery pressure (mPAP) is a standard parameter, using fordiagnosis of pulmonary hypertension (PHT).1 However, its measurement needs an invasive pulmonary artery catheter (PAC) placement. The B-lines are common lung artifacts associated with interlobular alveolar septa thickening; derive fromnon-invasive lung ultrasound (LUS) method. While the correlation between the B - lines and pulmonary capillary wedge pressure exist,2 the correlation between the B - lines and mPAP isnot verified in cardiac surgical patients. We hypothesized that the B - lines score is correlated with mPAP, and might be a useful parameter for guiding diagnosis of PHT.

Methods: We conducted a prospective obser-vational study in cardiac surgical intensive care unit (ICU), Phramongkutklao Army Hospital. We enrolled 32 post-cardiac surgical patients who received a PAC as part of standard care. LUS was performed in all patients within 6 hours postoperatively, and the sum of B-lines wasanalyzed asinternational recommen-dation.3 Pulmonary artery pressure variables (systolic pulmonary artery pressure (sPAP), diastolic pulmonary artery pressure (dPAP), and mean pulmonary artery (mPAP)) weresi -multaneously recorded while LUS was performing. Primary outcome wasthe correlation between B-line scores and mPAP, secondary outcomes included correlation between B-lines scores vs.s PAP, dPAP, and 1 - hr postoperative PaO2/FiO2ratio. Linear regressions were analyzed using SPSS v.17.0.

Result: All32 patients were ASA class 3, and underwent elective cardiac surgeryincluding coronary artery bypass graft surgery (CABG) (n = 28), valvularheart surgery (n = 2), and combined CABG withvalvularheart surgery (n = 2). We foundasignificant correlation between B - lines scores and mPAP (r2 = 0.36, p < 0.001), B - lines scores and sPAP (r2 = 0.2, p = 0.01), and B - lines scores and dPAP (r2 = 0.1, p = 0.03). There was no correlation between B - lines scores and 1 - hr postoperative PaO2/FiO2 ratio (r2 = 0.03, p = 0.33).

Conclusions: In post-cardiac surgical patients, the B - lines scoressignificantly correlated with mPAP, sPAP, and dPAP. However, their correlation was weak. To guide diagnosis of PHT using the B - lines scores, further well - conducted studies with more number of patients, including patients with PHT, are needed to validate our findings.