Relationship between nt-probnp and extravascular lung water in ards

Introduction

Natriuretic peptides have become important tools for diagnosis, risk stratification and therapeutic decision making for patients with heart failure and hydrostatic pulmonary edema. However, the practical use of N-terminal pro-brain natriuretic peptide (NT-proBNP) in ARDS patients and its relationship with non-cardiogenic pulmonary edema remain controversial.

Objectives

To evaluate the relationship between plasma concentrations of NT-proBNP, hemodynamics and extravascular lung water and to assess the possibility of using NT-proBNP to diagnose pulmonary edema in ARDS.

Methods

Fifteen adult patients with mean age of 43 (27-50) years with diagnosed ARDS according to Berlin definition were enrolled into an observational one-center prospective pilot study. The patients received hemodynamic monitoring using transpulmonary thermodilution (PiCCO₂, Pulsion Medical Systems, Germany) with measurement of mean arterial pressure, cardiac index (CI), central venous pressure, global end-diastolic volume index (GEDVI), systemic vascular resistance index and extravascular lung water index (EVLWI). Hemodynamic, respiratory parameters and plasma concentrations of NT-proBNP were assessed on the day of admission and on days 3 and 5 of hospitalization. Patients received goal-directed therapy using CI, GEDVI and EVLWI. The statistical analysis was performed using Mann-Whitney U-test and Spearman's correlation coefficient. The data are presented as median (25th-75th percentiles).

Results

The causes of ARDS included severe pneumonia (33%), sepsis (33%), multiple trauma (27%) and acute poisoning (7%). On admission, 8 patients had mild, 5 - moderate and 2 - severe ARDS. The ICU mortality was 27% (4 patients). The mean plasma concentrations of NT-proBNP in ARDS patients were higher than the normal values, with a trend for decrease during hospitalization: from 4706 (334-15173) pg/ml on admission to 1843 (118-10815) pg/ml and 1236 (332-11100) pg/ml on days 3 and 5, respectively (p > 0,05). The plasma concentration of NT-proBNP on admission in patients with mild ARDS was 325 (107-4059) pg/ml vs. 17541 (3797-40795) pg/ml in the group of patients with moderate and severe ARDS (p = 0,028). On admission, NT-proBNP correlated with GEDVI (rho = 0,615; p = 0,025), which was 701 (652-910) ml/m². We did not find correlation of plasma NT-proBNP with CI and EVLW.

Conclusions

In ARDS patients, we observed increased plasma concentrations of NT-proBNP on admission with a trend for decrease over time. In moderate and severe ARDS, NT-proBNP concentrations are higher than in mild ARDS. The plasma concentrations of NT-proBNP correlate with GEDVI; however we observed no relationship of NT-proBNP with CI and EVLW. Thus, NT-proBNP has a limited value to diagnose pulmonary edema in ARDS.