Brain natriuretic peptide in acute brain diseases

Introduction

Brain natriuretic peptide (BNP) is a member of the family of natriuretic peptide hormones, which are involved in regulation of sodium and water homeostasis. It has been proven that natriuretic peptide plays a role in sodium dysbalance in acute brain diseases, especially in Cerebral Salt Wasting Syndrome (CSWS). It is also elevated in intracranial hypertension. Now there is a method available that can assay an N terminal fragment pro brain natriuretic peptide (NT-proBNP).

Method

We retrospectively analysed 77 blood samples for NT-proBNP from 18 patients hospitalised at our ICU from February until May 2002. Seventeen patients had acute brain disease (sub-arachnoid hemorrhage [SAH], eight cases; intracerebral hemorrhage, one case; tumor, five cases; and others, five cases) and one patient had spine disease.

All patients were classified as NYHA I, and their age was between 23 and 73 years (mean age 53 years).

We investigated NT-proBNP, serum osmolality (S_osm) and sodium (S_Na⁺) on day 1. S_osm, S_ Na⁺, daily urinary loss of sodium (dU_Na⁺), creatinine clearance (C_krea), diuresis, income of fluids and sodium in 24 hours on day 2. Moreover, we assessed NT-proBNP changes in time. Upper reference range for NT-proBNP is 150 pg/l.

Results

Parameters ± standard deviation (SD) and correlation coefficients (r) are presented in Table 1.

Table 1

NT-proBNP was significantly elevated in all the patients (P = 0.007) and the value did not significantly change in time (difference between two samples in 13 patients; P = 0.3), and in tree samples in eight patients (P = 0.28, P = 0.37). NT-proBNP had no correlation with other parameters measured.

Conclusion

In our retrospective study we found significant elevation of NT-proBNP in patients with acute brain disease and without sodium dysbalance. Values of NT-proBNP did not significantly change in time and did not correlate with any biochemical parameters measured.