Changes in N-terminal pro-brain natriuretic peptide correlate with fluid volume changes assessed by bioimpedance in peritoneal dialysis patients.
OBJECTIVE
Both brain natriuretic peptide (BNP) and volume overload are reported to be powerful predictors of survival for peritoneal dialysis patients. The usefulness of single BNP determinations in helping determine volume status in peritoneal dialysis patients remains controversial, so we reviewed serial BNP and multifrequency bioimpedance measurements to determine whether changes in BNP reflected changes in volume status.


METHODS
Prospective measurements of fluid volume by multifrequency bioimpedance and serum N-terminal pro-BNP (NTproBNP) were conducted in stable adult peritoneal dialysis outpatients attending for routine assessments of peritoneal dialysis adequacy and transport status.


RESULTS
A total of 189 serial measurements were made in 92 patients, and NTproBNP increased from a median of 162.5 pmol/l (interquartile range 82-385.4) to 195 pmol/l (interquartile range 101.9-348.6; p < 0.05). Changes in NTproBNP correlated with changes in extracellular water (ECW), total body water (TBW) and ECW/TBW (r = 0.38, 0.31 and 0.45, respectively; all p < 0.0001). Patients were divided into quartiles depending upon NTproBNP changes; those with the greatest fall in NTproBNP had significant falls in ECW (p < 0.001), TBW (p = 0.001) and ECW/TBW (p < 0.001) compared to the quartile with the greatest increase in NTproBNP, who also had an increase in systolic blood pressure from 133.5 ± 22.7 to 142.7 ± 28.8 mm Hg (p = 0.0078), whereas it fell in the quartile with the greatest fall in NTproBNP (143.8 ± 24.6 vs. 136.5 ± 18.7 mm Hg).


CONCLUSIONS
Serial measurements of NTproBNP correlated with changes in volume assessments made by multifrequency bioimpedance in peritoneal dialysis outpatients. As multifrequency bioimpedance measures total ECW, rather than effective plasma volume, serial NTproBNP determinations may prove an adjunct to the clinical assessment of volume status in peritoneal dialysis patients.
UCL Centre for Nephrology, Royal Free Hospital, University College London Medical School, London, UK. andrewdavenport @ nhs.net
Andrew
A
Davenport
D001826:Body Fluids / Q000378:metabolism; D019295:Computational Biology; D045604:Extracellular Fluid / Q000378:metabolism*; D005260:Female; D006801:Humans; D007676:Kidney Failure, Chronic / Q000378:metabolism* / Q000401:mortality / Q000628:therapy*; D008297:Male; D008875:Middle Aged; D020097:Natriuretic Peptide, Brain / Q000097:blood*; D010045:Outpatients / Q000706:statistics & numerical data; D010446:Peptide Fragments / Q000097:blood*; D010530:Peritoneal Dialysis / Q000401:mortality; D011237:Predictive Value of Tests; D012307:Risk Factors; D014883:Water-Electrolyte Imbalance / Q000378:metabolism / Q000401:mortality / Q000628:therapy
D010446:Peptide Fragments; C109794:pro-brain natriuretic peptide (1-76); D020097:Natriuretic Peptide, Brain