Activation of the clotting system: heparin-coated versus non coated systems for extracorporeal circulation.
The purpose of this experimental study was to compare heparin-coated versus non-coated systems for extracorporeal membrane oxygenation (ECMO), to investigate the dynamic course of clotting activation in both groups.


METHODS
Eight pigs weighing 19.7 (+/- 1.3) kg, each underwent ECMO for 24 hours. Two groups were formed: in group 1, heparin-coated circuits were used with low dose heparinization (10 IU/kg/hr), whereas in group 2 non-coated circuits with high dose heparinization (60 IU/kg/hr) were used. Coagulation was monitored by measuring prothrombin time, partial thromboplastin time, fibrinogen, antithrombin III (AT III) and specific markers of clotting activation (thrombin-antithrombin III complexes (TAT) and D-dimer). Furthermore, platelet count, hematocrit, activated clotting time (ACT), and plasma heparin concentration were determined regularly


RESULTS
The dynamic course of the specific coagulation activation markers showed some differences: whereas TAT and D-dimer increased quickly in group 2, the increase in group 1 was delayed. Activation marker values tended to be lower in group 1 during the first six hours, after which no more differences between the groups were seen. After 24 hours of ECMO, TAT and D-dimer had nearly returned to baseline values. Platelets showed a continuous decrease throughout the experiment, which was very similar in both groups.


CONCLUSIONS
The heparin coated system showed a distinct delay in clotting activation during the first six hours of ECMO. After six hours there were no more differences between the groups.
Urlesberger
B
B
ECMO Center Graz (Department of Neonatology), University of Graz, Austria. berndt.urlesberger@kfunigraz.ac.at
Zobel
G
G
Rödl
S
S
Dacar
D
D
Friehs
I
I
Leschnik
B
B
Muntean
W
W
D000818:Animals; D000925:Anticoagulants / Q000494:pharmacology*; D000990:Antithrombin III / Q000032:analysis; D001672:Biocompatible Materials; D001777:Blood Coagulation / Q000187:drug effects*; D015199:Extracorporeal Membrane Oxygenation; D005260:Female; D005340:Fibrinogen / Q000032:analysis; D006400:Hematocrit; D006493:Heparin / Q000097:blood / Q000494:pharmacology*; D008297:Male; D008567:Membranes, Artificial; D010314:Partial Thromboplastin Time; D010447:Peptide Hydrolases / Q000032:analysis; D010976:Platelet Count; D011517:Prothrombin Time; D013552:Swine
D000925:Anticoagulants; D001672:Biocompatible Materials; D008567:Membranes, Artificial; C046193:antithrombin III-protease complex; D000990:Antithrombin III; D005340:Fibrinogen; D006493:Heparin; D010447:Peptide Hydrolases