Characterization of "refilling types" by continuous blood volume monitoring during hemodialysis.

Fluid removal during HD is frequently associated with acute hypotension due to insufficient mobilization of extravascular fluid and subsequent hypovolemia. Large variability in vascular refilling makes dialysis therapy difficult and requires a better understanding of fluid distribution in the individual hemodialysis (HD) patient. Blood volume monitoring was performed by continuous measurement of blood density with a DMA 46 Density Meter (Fa. Chempro, PAAR, Austria) in six patients on regular HD treatment. A body filtration coefficient (CF = extra/intravascular fluid shift) was calculated using a computer model by Schneditz et al (1990) and blood density was measured during a 60-minute ultrafiltration period (1/3 x delta kg/hr = 19 +/- 4 ml/min). Concerning blood density differences (delta f%) and body filtration coefficient (CF) there was a wide inter-individual range (delta f = 2.8-8.0%, CF = 3-9 ml/mm Hg/min), but there was a good intraindividual reproducibility of delta f and CF. A negative correlation (r = -0.95) between delta f and CF could be established. The severity of hypotensive episodes and frequency of interventions correlated well with delta f and CF; severe symptoms occurred with a delta f > 6% and a CF < 4 ml/mm Hg/min. These results suggest that improvement in dialysis therapy can be achieved by blood volume monitoring and classification of "refilling types." By blood volume-controlled computerized sodium and UF profiles, a reduction of hypotensive episodes and emergency intervention might be possible.