Transthoracic ultrasound assessment of B-lines for identifying the increment of extravascular lung water in shock patients requiring fluid resuscitation

Introduction:

Several studies have shown that the number of B-lines was related to the amount of extravascular lung water (EVLW). In our study, we aimed to demonstrate the magnitude of the incremental B-lines in shock patients with positive net fluid balance and the association with gas exchange impairment.

Materials and Methods:

We performed trans-thoracic ultrasound at admission (T₀) and at follow-up period (T_FL) to demonstrate the change of B lines (ΔB-lines) after fluid therapy. We compared the total B-line score (TBS) at T₀ and T_FL and calculated the Pearson''s correlation coefficient between the ΔB-lines and PaO₂/FiO₂ ratio.

Results:

A total of 20 patients were analyzed. All patients had septic shock. Net fluid balance was + 2228.05 ± 1982.15 ml. The TBS at T₀ and T_FL were 36.6 ± 23.73 and 63.80 ± 29.25 (P < 0.01). The ΔB-lines along anterior axillary line (AAL) correlated to the ΔTBS (r = 0.90, P < 0.01). The ΔB-lines along AAL had inverse correlation to PaO₂/FiO₂ ratio (r = −0.704, P < 0.05). The increase of B-lines ≥ 10 was related to the decrease of PaO₂/FiO₂ ratio. The inter-observer reliability between two ultrasound readers was high (r = 0.92, P < 0.01).

Discussion:

The number of B-lines increased in shock patients with positive net fluid balance and correlated to impaired oxygenation. These data supported the benefit of ultrasound for assessing the EVLW.