N-terminal pro-B-type natriuretic peptide with fractional excretion and clearance of sodium in relation to cardiovascular events after elective cervical spine surgery.

OBJECTIVES: N-terminal pro-B-type natriuretic peptide (NT-proBNP) is increasingly being used as a biomarker of cardiovascular risk. To date neither its cut-off for postoperative period in noncardiac surgery nor whether the cardiovascular risk has any relation to natriuresis has been assessed.

DESIGN: The prospective observational study evaluated postoperative serum levels of NT-proBNP with fractional excretion of sodium (FENa+) and sodium clearance (CNa+) in relation to the occurrence of cardiovascular events in patients after elective cervical spine surgery.

METHODS: In 27 otherwise healthy patients after elective cervical spine surgery we prospectively measured serum NT-proBNP and serum sodium immediately after the operation (day 1) and on day two. We correlated both NT-proBNP with FENa+, CNa+, diuresis and intake of fluids and sodium, which were assessed from the beginning of the operation until day two. We followed the incidence of myocardial infarction, heart failure and cardiac death postoperatively to 1 year.

RESULTS: Immediate postoperative NT-proBNP values were within the reference range (mean 4.53 ± 2.48 pmol/l), but they increased significantly on the second day (mean 23.57 ± 12.27 pmol/l, p<0.001). Significantly elevated CNa+ (0.033 ± 0.014 ml/s, p<0.001), FENa+ (0.018 ± 0.008, p<0.001) and fUNa+ (mean 326.9 ± 125.2 mmol, p<0.01) were found. There was a significant positive correlation between the two values of NT-proBNP (r=0.47, p=0.014), but we did not find any correlation between NT-proBNP and the further measured parameters. None of the patients had any cardiovascular events from operation until 1 year.

CONCLUSIONS: The significant postoperative elevation of NT-proBNP had no relationship with the rise in FENa+, CNa+ or fUNa+ and was not connected with any occurrence of cardiovascular events in patients after elective cervical spine surgery.

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