Undetectable brain natriuretic peptide as a marker of ultrasound-detected hypovolemia in patients with cancer on active treatment

Hypovolemia is a common complication in patients undergoing cancer-related therapies, yet assessing volume status in this population is challenging because of confounding comorbidities. This retrospective study is the first of its kind to examine the relationship between hypovolemia, assessed by measuring inferior vena cava (IVC) diameter via transthoracic echocardiogram (TTE) as an indicator of fluid status, and brain natriuretic peptide (BNP) levels, a cardiac neurohormone released by the ventricles in response to increased pressure. We hypothesized that undetectable BNP levels (<10 pg/mL) would associate with small IVC diameters indicative of hypovolemia. Although our study revealed wide confidence intervals reflective of a small sample size, our findings suggest that undetectable BNP, a readily available laboratory marker, may serve as an indicator of hypovolemia when physical examination findings are inconclusive. In addition, our study was limited by the 2-week temporal variability of BNP and IVC measurements, which may potentially introduce bias because of the dynamic fluctuation of volume status. Further studies with larger cohorts and closer temporal alignment of BNP and TTE measurements are needed to validate these findings.