Surrogate markers of pulmonary edema and severity of lung injury do not accurately reflect measured extravascular lung water

Introduction
Determination of extravascular lung water (EVLW) by transpulmonary thermodilution predicts progression to acute lung injury (ALI). Early identification of patients at risk for developing ALI may impact clinical decision-making. Measurement of EVLW, however, is invasive, requiring central venous and arterial catheters. We asked whether less invasive clinical parameters and markers of severity of lung injury could be used to estimate lung water, obviating the need for the more invasive determination.

Methods
Eighteen patients at risk for ALI due to massive aspiration (n = 1), sepsis (n = 16), massive transfusion (n = 1), and/or trauma (n = 2) were studied prospectively. The PaO2/FiO2 ratio, central venous pressure (CVP), Vd/Vt, fluid balance, Cs, and Lung Injury Scores (LIS) were compared with the EVLW measured on the same day by linear regression analysis (Figure 1).

Results
Poor correlation of EVLW with the PaO2/FiO2 ratio (r2 = 0.0061), CVP (r2 = 0.1261), fluid balance (r2 = 0.0903), Vd/Vt (r2 = 0.0135), Cs (r2 = 0.0014), and LIS (r2 = 0.0837) was seen (Figure 1).

Conclusion
The clinical parameters examined in this study do not accurately reflect the EVLW and should not be used as surrogates for it.