Objective: Hypotension and decreased serum atrial natriuretic peptide (ANP) in response to hemodialysis have both been attributed to a decrease in central blood volume. The aim of this study was to test whether circulatory performance and serum ANP were related to changes in central blood volume, in conjunction with hemodialysis with loss of plasma volume.
Material and methods: Ten uremic patients without cardiopulmonary symptoms were investigated before, immediately after and 2 h after a regular dialysis session. Bolus indocyanine green dilution was used for the measurements of central blood volume, cardiac output and stroke volume. Serum ANP was analyzed using a radioimmunoassay technique.
Results: Hemodialysis resulted in a 3.8 +/- 1.3 kg decrease in weight and an increase in hemoglobin concentration, while central blood volume, stroke volume, cardiac output, blood pressure and serum ANP fell in parallel. Two h after dialysis, central blood volume recovered to its pre-dialytic level, whereas weight, plasma volume, stroke volume, blood pressure and serum ANP stayed at low levels. There were strong correlations between serum ANP and hemoglobin concentration, stroke volume, cardiac output and blood pressure, but not between serum ANP and central blood volume. Correlations between central blood volume and plasma volume, stroke volume, cardiac output, and blood pressure were also weak.
Conclusions: The close correlation between circulatory performance and serum ANP implies a reduction in preload in response to dialysis. The lack of correlations between central blood volume and circulatory performance and serum ANP suggests that the compliance in the central vasculature is increased in response to dialysis.