The plasma kinetics of hydroxyethyl starch 350/0.60: a potential new adjunct for centrifugal leucapheresis.

A modified species of hydroxyethyl starch (HES 350/0.60) possessing a Mw- of 350,000 daltons combined with a molar hydroxyethyl group substitution (MS) of 0.60 (60 hydroxyethyl groups.100 glucose residues) was clinically assessed in seven normal subjects to determine the influence of these chemical modifications on intravascular clearance kinetics concomitantly with effects on the suspension stability (ESR) of blood. Following a standardised intravenous dose (30 gm.m2 BSA), the concentration of HES 350/0.60 in serum fell to half its peak value in 11.8 +/- 1.3 (SD) hours, while the ESR remained elevated for up to 12 hours post-injection. By adopting a Mw- of 350,000 daltons, the critical molecular weight (Cmw) of this colloid was surpassed, while the critical concentration (Cc), below which the suspension stability of blood is not affected, was shown to range between 0.3 and 0.5 gm.dl-1. In comparison to the present species of HES (Mw- 450,000 daltons, MS: 0.70) utilised as a sedimenting agent duirng centrifugal leucapheresis, HES 350,000/0.60 appears to affect the ESR in a similar manner, but is removed from the intravascular space approximately twice as rapidly. This more rapid clearance should be useful in avoiding cumulative build-up of HES in blood concomitant with reducing the total amount of intravascular H2O bound to this colloid, in normal and CML donors undergoing multiple cell collection procedures.