Infusion of plasma expanders may lead to unexpected results in urinary protein assays

Overt proteinuria was detected in the urine of a potential kidney donor, ultimately leading to the refusal of the kidneys for transplantation purposes. Histological examination of the kidneys did not reveal any abnormalities. Searching for substances that could have interfered with the urinary total protein assay, the role of infused, modified gelatin plasma expanders was investigated. We therefore measured the concentration of protein before and after the addition of various artificial plasma expanders to urine. Only when Biuret reagent or Pyrogallol Red dye were used did we find elevated concentrations of protein. Other methods, including the turbidimetric assays, did not detect additional amounts of protein in the spiked urine. We conclude that the infusion of modified gelatin solutions may cause apparent proteinuria. This effect is not observed with starch-based plasma expanders. Clinical chemists and clinicians should be aware of this phenomenon and possibly repeat the analysis with a different technique.

Pharmacokinetics of oxypolygelatine in healthy volunteers

OBJECTIVE/METHODS

The pharmacokinetics of the plasma substitute oxypolygelatine (OPG) were studied in 12 healthy volunteers after single-dose administration of 27 ml x kg(-1) body weight, with a maximum of 2000 ml. OPG was determined in plasma and urine over 48 h after the infusion. Peak plasma OPG concentrations at the end of the infusion were determined to 4.600 (623) microg x ml(-1), the area under the plasma concentration/time curve (AUC(0-infinity)) was calculated to 70.135 (15.861) microg x h x ml(-1).

RESULTS

The model-independently calculated volume of distribution came to 23.1 (4.8) 1 with a clearance total is (Cl(tot)) of 24.6 (6.8) ml x min(-1). The initial half-life according to a three-compartment model came to 0.3 (0.2) h, followed by a distribution half-life of 3.1 (2.6) h and a terminal elimination half-life of 13.4 (2.2) h. Cumulative urinary excretion of OPG was 64% after 48 h.

CONCLUSION

This low recovery rate may be explained by the distribution of OPG into the extravascular space and subsequent degradation in tissue sites.