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The effects of variations in thoracic blood volume and intravenous sodium loading on plasma levels of NTproANP and NTproBNP in healthy volunteers


The N-terminal prohormones of the natriuretic peptides ANP and BNP (NTproANP and NTproBNP) are accepted markers of myocardial dysfunction [1] and are increasingly used in critically ill patients. While it is well recognized that plasma levels of ANP are altered by variations in thoracic blood volume and during intravenous sodium loading [2], only incomplete data are available on the course of BNP during these interventions [3].

Materials and methods

Two groups of eight healthy subjects were randomly tilted into a 15°-feet-down (FD) or a 15°-head-down (HD) position. Ten volunteers were crossover subjected to an infusion of 15 ml/kg NaCl 0.9% (over 60 min) or control during an observation period of 10 hours. Blood was sampled at timed intervals. NTproANP and NTproBNP were determined by radiochemiluminescence and electrochemoluminiscence immunoassays, respectively.


NTproANP levels (in % of baseline levels) were higher (P < 0.05) during HD (124 ± 13%) than during FD (82 ± 6%), while NTproBNP levels were not affected by tilting. Following sodium loading (Fig. 1), plasma NTproANP levels increased immediately and returned back to baseline after 8 hours. In contrast, NTproBNP levels increased 3 hours after infusion and had doubled at the end of the observation period.

Figure 1
figure 1

The course of plasma levels of NTproANP and NTproBNP in 10 healthy volunteers during the control protocol () and the sodium loading protocol (□). Data are mean ± SEM. *P < 0.05, between-group difference. §P < 0.05, versus baseline value. Friedman's test and Wilcoxon's matched pairs test as appropriate.


Besides relevant physiological implications – a sequential increase of NTproANP and NTproBNP after sodium loading has not been shown previously in humans – our data show that NTproBNP levels are influenced by sodium infusion. This may be relevant for the interpretation of NTproBNP levels in critically ill patients.


  1. Mueller T, Gegenhuber A, Poelz W, Haltmayer M: Comparison of the Biomedica NT-proBNP enzyme immunoassay and the Roche NT-proBNP chemiluminescence immunoassay: implications for the prediction of symptomatic and asymptomatic structural heart disease. Clin Chem 2003, 49: 976-979. 10.1373/49.6.976

    Article  PubMed  Google Scholar 

  2. Hollister AS, Tanaka I, Imada T, Onrot J, Biaggioni I, Robertson D, Inagami T: Sodium loading and posture modulate human atrial natriuretic factor plasma levels. Hypertension 1986, 8: 106-111.

    Article  Google Scholar 

  3. Lang CC, Choy AM, Turner K, Tobin R, Coutie W, Struthers AD: The effect of intravenous saline loading on plasma levels of brain natriuretic peptide in man. J Hypertens 1993, 11: 737-741.

    Article  CAS  PubMed  Google Scholar 

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Heringlake, M., Heide, C., Klaus, S. et al. The effects of variations in thoracic blood volume and intravenous sodium loading on plasma levels of NTproANP and NTproBNP in healthy volunteers. Crit Care 8 (Suppl 1), P49 (2004).

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