Serum B-type natriuretic peptide: a marker of fluid resuscitation after injury?

BACKGROUND: Excessive volume resuscitation after injury is associated with severe complications. B-type natriuretic peptide (BNP) is secreted from myocardium under increased wall stretch and is used in medical intensive care units (ICUs) as a noninvasive method to detect heart failure. However, the use of BNP as a marker of fluid overload during resuscitation from injury has not been previously described.
METHODS: Serum BNP levels were prospectively followed in 134 trauma ICU patients. Levels were obtained at admission and at 12, 24, and 48 hours. Repeated measures analysis of variance was used to test for differences in BNP levels over time. Post hoc pairwise comparisons were made with Bonferroni correction when the omnibus test indicated significance. Chest films were obtained at 24 hours and scored for the presence of pulmonary edema by a radiologist blinded to BNP measurements (n = 45). Twenty-four hour BNP levels for patients with or without radiographic evidence of pulmonary edema were compared using nonparametric analysis (Mann-Whitney U).
RESULTS: Admission BNP levels were low and increased with fluid resuscitation over time in all patients (p = 0.002) as well as in a subgroup of patients <60 years of age (p = 0.003). At 24 hours, 25 patients had no pulmonary edema evident on chest X-ray, whereas 20 were scored indicating that pulmonary edema was present. Patients with evidence of pulmonary edema had higher mean BNP levels at 24 hours (110 +/- 31 pg/mL) than did patients without edema (47.0 +/- 10.8 pg/mL) (p = 0.04).
CONCLUSIONS: Serum BNP levels increase with resuscitation after injury and levels are higher in patients who develop pulmonary edema. These findings suggest that BNP might be a marker of excessive volume resuscitation after injury.