Extravascular Lung Water, B-Type Natriuretic Peptide, and Blood Volume Contraction Enable Diagnosis of Weaning-Induced Pulmonary Edema*

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Abstract

Objective:

We tested whether the changes in extravascular lung water indexed for ideal body weight could detect weaning-induced pulmonary edema. We also studied the diagnostic value of blood volume contraction indices and B-type natriuretic peptide variations.

Design:

Prospective study.

Setting:

ICU.

Patients:

Twenty-one patients who failed a first spontaneous breathing trial.

Interventions:

None.

Measurements and Main Results:

We performed a second 60-minute T-tube spontaneous breathing trial. Before and at the end of spontaneous breathing trial, we recorded pulmonary artery occlusion pressure, the extravascular lung water indexed for ideal body weight, plasma B-type natriuretic peptide level, hemoglobin, and plasma protein concentrations. Weaning-induced pulmonary edema was defined by the association of signs of clinical intolerance and a pulmonary artery occlusion pressure greater than or equal to 18 mm Hg at the end of spontaneous breathing trial. Because some patients performed several spontaneous breathing trial, a primary analysis included all spontaneous breathing trial and a secondary analysis included only the first spontaneous breathing trial of each patient. In primary analysis, 36 spontaneous breathing trials were analyzed, 21 spontaneous breathing trial with weaning-induced pulmonary edema and 15 without. During spontaneous breathing trial, extravascular lung water indexed for ideal body weight increased only in cases with weaning-induced pulmonary edema (25% ± 23%). Plasma protein concentration, hemoglobin concentration, and B-type natriuretic peptide also significantly increased only in cases with weaning-induced pulmonary edema (9% ± 3%, 9% ± 4%, 21% ± 23%, respectively). The areas under the receiver operating characteristics curves to detect weaning-induced pulmonary edema were 0.89 (95% CI, 0.78–0.99) for extravascular lung water indexed for ideal body weight, 0.97 (0.93–1.01) for spontaneous breathing trial–induced changes in plasma protein concentration, 0.96 (0.90–1.01) for changes in hemoglobin concentration, and 0.76 (0.60–0.93) for changes in B-type natriuretic peptide. An increase in extravascular lung water indexed for ideal body weight greater than or equal to 14% diagnosed weaning-induced pulmonary edema with a sensitivity of 67% (95% CI, 43–85%) and a specificity of 100% (95% CI, 78–100%). The secondary analysis confirmed these results.

Conclusions:

Spontaneous breathing trial–induced increases in extravascular lung water indexed for ideal body weight, plasma protein concentrations, hemoglobin concentration, and B-type natriuretic peptide are reliable alternatives to the pulmonary artery catheter for diagnosing weaning-induced pulmonary edema.

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