Celite and Kaolin Produce Differing Activated Clotting Times during Cardiopulmonary Bypass under Aprotinin Therapy

Abstract

Since the introduction of the proteinase inhibitor aprotinin in cardiac surgery, a strong increase of the activated clotting time (ACT) during the extracorporeal circulation phase (ECC) was reported in many clinical studies, but with a lack of correlation between ACT and heparin concentration. In searching for a cause of this inconsistency we investigated different surface activators of the ACT in a clinical study. During ECC ACT was measured in parallel, using a Hemochron device and corresponding tubes (nominally 12 mg celite activator) for celite ACT, and a HemoTec device with corresponding double tubes (nominally 0.1 ml kaolin activator) for kaolin ACT. Under the conditions of ECC, the kaolin ACT values (482 +/- 145 sec) were significantly lower than the celite ACT values (985 +/- 267 sec). These results were confirmed in ex-vivo experiments using an activated partial thromboplastin time (aPTT) model. With heparin alone, aPTT activated with celite and kaolin were similar. Including aprotinin in this model, the celite aPTT showed no correlation to the heparin concentration, whereas the kaolin aPTT remained well correlated to the heparin concentration and similar to the values without aprotinin. With aprotinin alone there were no changes of the aPTT times, whereas the celite ACT times were without any correlation. Our results indicate that using kaolin instead of celite the ACT measurements under aprotinin therapy stay in the same ranges as without application of aprotinin: aprotinin has no detectable influence on kaolin-activated ACT. In our opinion, kaolin should be used as the surface activator for ACT measurements under the conditions of ECC, heparinization, and aprotinin therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Point-of-Care Testing for Anticoagulation Monitoring in Neuroendovascular Procedures

“…All available devices have acceptable reproducibility, but reference and therapeutic ACT ranges vary considerably. 21,26,27 Therefore, every ACT test should be regarded as unique.…”

“…21,25 Another example is aprotinin, which affects Celitebased ACT but not kaolin-based ACT. 26 Venous ACT was found to be slightly but significantly greater than arterial ACT in 1 prospective study that sampled arterial and venous blood in 48 patients undergoing PCI. 35 This difference, however, did not affect the complication rate or the amount of heparin used during the procedure.…”

“…Heparin-independent factors include hemodilution, concentration of clotting factors, hypofibrinogenemia and other coagulopathies, hypothermia, and platelet count. 26,33 Recent data suggest that there may be a difference in heparin sensitivity among races.…”

Aprotinin does not prolong the Sonoclot aprotinin-insensitive activated clotting time

“…Activated clotting time values obtained in the presence of aprotinin can yield substantial variability with different activators [3,4]. Celite ACT (SonACT) values are prolonged in vitro with commonly used doses of aprotinin during heparin anticoagulation [3,5].…”

“…Celite ACT (SonACT) values are prolonged in vitro with commonly used doses of aprotinin during heparin anticoagulation [3,5]. The impact on the kaolin is less, and thus, kaolin ACT (kACT) is an alternative to the SonACT [2][3][4][5]. However, even kACT is significantly prolonged in the presence of aprotinin [5].…”