Summary
Artificial colloids based on gelatin are used as plasma expander to replace donor
blood products. In laboratory experiments, gelatin reduced both the velocity and extend
of platelet agglutination by ristocetin, and only the agglutination velocity by polybrene
(p <0.05). Furthermore, gelatin delayed the in-vitro platelet plug formation under
shear-stress in the absence of ADP (p <0.05), whereas gelatin induced no delay in
the presence of ADP. Thus, after induction of vWF release from platelets by polybrene
or ADP, platelet function was normal. These results indicate that gelatin affects
in particular the functionality of plasma-vWF and partly inhibits platelet adhesion.
These negative effects of gelatin on hemostasis were demonstrated in two clinical
studies during cardiac surgery. In a randomized study of sixty patients undergoing
cardiac surgery, gelatin as prime in the heart-lung machine appeared to result in
diminished efficacy of aprotinin on hemostasis, whereas it did not affect hemostasis
in non-aprotinin patients. An additional retrospective clinical study showed that
only high dose of gelatin affected hemostasis. This suggests a limited role of plasma-vWF
and a strong back-up mechanism of platelet-vWF in achieving hemostasis.
