Blood volume and brain natriuretic peptide in congestive heart failure: a pilot study

Brain natriuretic peptide (BNP) levels rise in response to stretch of ventricular myocytes or increases in wall tension, as in congestive heart failure (CHF). Brain natriuretic peptide can be released in bursts, but nonetheless, BNP levels may lag behind clinical changes. We postulated that concomitant measurement of blood volume (BV), BNP, and hemodynamics during treatment of CHF may elucidate interrelationships among changes in these parameters.

We studied 10 male patients, aged 60 +/- 8 years, who were admitted for pulmonary catheter-guided treatment of CHF. Hemodynamics, venous BNP, and blood and plasma volumes were measured at baseline before treatment and again on the following morning after 12 to 24 hours of acute treatment for CHF.

At baseline, all 10 patients exhibited marked expansion of BV at 29% +/- 19%. At baseline, increased systolic pulmonary artery pressure correlated with BV (r = 0.615) and diastolic pulmonary artery pressure (PAD) with BV (r = 0.609). After treatment, there was an inverse correlation between change (decline) in expanded BV and change (improvement) in mixed venous oxygenation (r = -0.775) and a positive correlation with central venous pressure (CVP) (r = 0.710). Poor correlation was found between BNP and any hemodynamic parameter. Little correlation was found between absolute BNP and BV before or after treatment (r = -0.127 and -0.126, respectively).

In this pilot study, changes in BV with treatment correlate better with hemodynamics than do changes in BNP, likely reflecting the lag in BNP response to treatment and its tendency to reflect long-term rather than instantaneous volume status. These preliminary data suggest that BV may be a more accurate guide in optimizing CHF treatment than BNP.