Performance of devices in medical applications (in vitro)

We determine the following performance parameters e.g. of hemodialyzers:

  • Clearance of low molecular weight solutes in aqueous solutions according to ISO 8637
  • Clearance of low molecular weight plasma proteins (LMWP) from blood and plasma
  • Determination of sieving coefficients of plasma proteins from plasma or human blood according to ISO 8637
  • Albumin loss into dialysate during hemodialysis und hemodiafiltration (online-HDF)
  • Determination of transmembrane pressure (TMP) in aqueous solution, plasma and human blood.
  • Determination of ultrafiltration rate (UFR) and ultrafiltration coefficient (KUF) in aqueous solution, plasma and human blood.

LMWP clearances or albumin loss is determined using freshly donated human blood or plasma supplemented with concentrated hemofiltrate obtained from end-stage renal disease (ESRD) patients. By this approach donor blood gets closer to the properties of uremic blood (e.g. with regard to the concentration of uremic toxins like β2-microglobulin).

In our in vitro dialysis model using original dialysis monitors and clinical size dialyzers we determine clearances of e.g. the following solutes

  • Urea
  • Creatinine
  • Phosphate
  • Cyanocobalamin (Vitamin B12)
  • Inulin

in dialysis fluids according to EN 8637 or ANSI/AAMI RD16.

We also offer standardized methods for clearance of plasma proteins, such as:

  • ß2– Mikroglobulin
  • Myoglobin
  • Cystatin C
  • Retinol binding protein (RbP)
  • α1-Microglobulin
  • etc. (directory of services)

in human donor blood or plasma. In parallel to the clearance measurements in human blood, plasma or albumin solution we can determine albumin loss into dialysate in vitro.

Finally, we can determine in vitro clearances across dialysis membranes of other substances, e.g. compounds, pharmaceuticals or ethical drugs as this asked by the EMEA to provide data on how e.g. pharmacokinetics of the compound may be altered in patients of hemodialysis.

Determination of sieving coefficients is carried out in in vitro-experiments using hemodialyzers, hemodiafilters, hemofilters or hemoconcentrators and a dialysis monitor in either human donor blood, plasma or albumin solution.

We determine sieving coefficients of e.g. the following proteins:

  • ß2-Mikroglobulin
  • Myoglobin
  • Cystatin C
  • Retinol binding Protein (RbP)
  • α1-Mikroglobulin
  • Albumin
  • other

in plasma or human blood according to EN 8637 or ANSI/AAMI RD16.

We are also experienced in characterizing highly porous membranes compared to dialysis membranes. Highly porous membranes are used in high cut-off filters, in artificial liver or in plasma fractionation and plasma separation. In standard experiments the following proteins, resp. particles are determined:

  • Albumin
  • IgG
  • HDL
  • Fibrinogen
  • LDL
  • IgM

TMP is the primary factor determining (ultra)filtration rate. During filtration, the feed side of the membrane is showing higher pressure than the permeate side. This pressure difference forces fluids such as plasma water to pass the membrane. Determination of transmembrane pressure is carried out in in vitro-experiments but also during clinical studies using a custom designed four point pressure measurement (P bloodin, P bloodout, P dialysatein, P dialysateout) data acquisition system.

Ultrafiltration rate is defined as the hourly (ultra)filtration in mL, per m² dialyzer area and mm Hg TMP. The efficacy of a particular ultrafiltration device in producing ultrafiltrate is called ultrafiltration coefficient (KUF). It is expressed as the ultrafiltration per hour in mL at a TMP of one mm Hg. Determination of UFR and KUF is carried out in in vitro-experiments and clinical studies and based on our four point TMP measurement. For protein containing solutions oncotic pressure can be taken into account by using the formula of Landis and Pappenheimer.