N-terminal B-type natriuretic peptide and renal function parameters in cerebral salt wasting syndrome

Introduction

Elevated levels of B-type natriuretic peptides are reported in hypo-osmolal hyponatraemia with natriuresis in cerebral salt wasting (CSW) syndrome. The aim of our study was to evaluate serum N-terminal pro-B-type natriuretic peptide (NT-proBNP) and its relationship with renal function parameters in patients with acute brain diseases who developed CSW.

Methods

We prospectively measured NT-proBNP in 12 patients (mean age 46 ± 17 years, seven men) with acute brain diseases (four subarachnoid haemorrhage, five tumour, three trauma, mean Glasgow Coma Scale 13 ± 2.7). All patients were classified as New York Heart Association (NYHA) I and none had pulmonary oedema. The mean Glasgow Outcome Scale upon discharge from the neurologic–neurosurgical ICU was 4 ± 1.2. Diagnoses of CSW (mean serum sodium 129 ± 3.6 mmol/l) were stated by evaluation of renal function parameters – only with clearance of creatinine above 1.15 ml/s. Urine was collected within 24 hours. The control group was made up of patients with acute brain diseases, normonatraemia, NYHA I and normal renal parameters (n = 20 patients).

Results

We found significantly higher levels of NT-proBNP in patients with CSW (430.4 ± 706.4 pg/ml) compared not only with the reference range (125 pg/ml, P = 0.001) but also with the control group (268.3 ± 203.9, P < 0.001). There were no differences in fluid intake (P = 0.440) between the two groups, but patients with CSW had higher sodium intake per kilogram of body weight (P = 0.024), diuresis (P = 0.019), daily sodium output (P = 0.036), electrolyte clearance (P = 0.001) and sodium clearance (P = 0.007). Further analysis of the control group did not show any relationship between NT-proBNP and measured parameters, in contrast to CSW, where we found a negative relation between NT-proBNP and serum sodium (P = 0.022), fluid intake (P = 0.047), osmotically active substances clearance (P = 0.031) and electrolyte clearance (P = 0.047). No further correlations were found.

Conclusion

Our results showed that natriuresis with hypo-osmolal hyponatraemia in CSW were related to significant higher serum levels of NT-proBNP with a negative correlation to serum sodium and fluid intake, compared with patients with acute brain disease and normonatraemia.