A Cut off Value for Brain Natriuretic Peptide Indicating Volume Overload in Hemodialysis Patients

Introduction: Accurate volume status evaluation leads to better control of hypertension and blood pressure in Hemodialysis (HD) patients, unfortunately there is lack of a reliable objective tool that can be used to measure volume status in daily clinical practice. Brain Natriuretic Peptide (BNP) is an important biomarker in patients with Chronic Kidney Disease (CKD). Whether it is a predictor of weight change or Blood Pressure (BP) response upon probing dry weight among hemodialysis patients remains unknown with lack of standardized cut off values in HD patients. Aim: To find a cut off value for BNP in HD patients with fair cardiac function which indicates concealed volume overload, to preserve cardiac function and reduce the risk of cardiovascular mortality on the long term. Method: 40 End-Stage Renal Disease (ESRD) patients on regular hemodialysis 3 times weekly were enrolled. Inclusion criteria: (1) Ejection fraction >55%, LV end systolic (2-4 cm) and diastolic (3.7-5.5 cm) internal dimensions by echocardiography. (2) Patients with mild LVH; intraventricular wall thickness in diastole <1.3 cm. (3) Hypertensive patients; with or without antihypertensive medications. Exclusion criteria: Patients with volume or pressure overload due to other causes than fluid overload (i.e. anemia, heart failure and aneurysmal dilatation of vascular access). Laboratory investigations were done with serum BNP samples collected post dialysis. Radiological studies included echocardiography, Inferior vena cava collapsibility index for assessment of volume status. Results: We found no statistical significant differences between hyper and normovolemic patients as regard patient’s characteristics including gender, smoking and presence of diabetes mellitus or hypertension. Also, no significant correlation was present between BNP and patient’s characteristics (age, gender) or laboratory investigations (S. Creatinine, S. Ca, Hb). However, there was an inverse relationship between BNP and IVC collapsibility index. Patients with hypervolemia had significantly higher BNP levels, as compared to the euvolemic patients, with a significant difference (p value=0.011) with the most relevant level of BNP (17.650 pg/ml) to differentiate hyper/normovolemic patients, with a sensitivity of 71% and a specificity of 77.8%. Conclusion: Our study would appear to provide direct evidence that plasma BNP levels were correlated to the degree of fluid retention in HD patients indicating that elevated levels of BNP could be regarded as a marker of volume overload in absence of other causes of volume and pressure overload (or in absence of heart failure, anemia or vascular access aneurysm).