To evaluate the relative antithrombotic efficacy and hemostatic safety of antithrombin therapy for vascular thrombus formation at sites of mechanical vascular injury, we administered the potent and specific irreversible synthetic antithrombin D-PHE-PRO-ARG chloromethyl ketone (D-FPRCH2Cl) after performing carotid endarterectomies in baboons. The continuous intravenous infusion of D-FPRCH2Cl, 100 nmol/kg per minute for 1 hour, abolished acute carotid endarterectomy thrombosis for at least 48 hours. The plasma level of D-FPRCH2Cl during the infusion was maintained steady at 7.2 ± 0.9 μmol/L, but decreased rapidly after discontinuing its infusion (T50 17 minutes). Platelet deposition, measured in real time using autologous 111In-platelet scintillation camera imaging, was 1.51 ± 0.40 × 108 platelet/cm in the 14 treated animals 90 minutes postoperatively, compared with 11.7 ± 1.16 × 108 platelet/cm in 14 heparin-treated controls (P < .002). The antithrombotic benefit was equivalent for treatment begun either 5 minutes before (nine animals) or 15 minutes after (five animals) reestablishing flow in the operated vessel, ie, 1.59 ± 0.36 × 108 platelet/cm versus 1.35 ± 0.51 × 108 platelet/min, respectively; P > .5. Endarterectomy thrombosis remained decreased for at least 48 hours post-operatively, as determined by the ratio between net 111Inplatelet radioactivity at the endarterectomized site versus whole blood (ratio 0.82 ± 0.25 in the treatment group v 3.03 ± 0.51 in heparin controls at 90 minutes, P < .005; and 0.85 ± 0.23 v 3.25 ± 0.48 at 48 hours, P < .002). The marked reduction in endarterectomy thrombosis in treated animals at 48 hours was confirmed by scanning electron microscopy. Thrombin activity formed rapidly and became immediately bound to thrombus on thrombogenic segments in untreated control studies; treatment with D-FPRCH2Cl irreversibly inactivated the thrombus-bound thrombin. Hemostatic function, as measured by bleeding time (BT), activated partial thromboplastin time (APTT), and prothrombin time (PT) was impaired throughout the intravenous administration of D-FPRCH2Cl (BT > 30 minutes, APTT > 150 seconds, PT > 50 seconds); BT, APTT, and PT values were normal 30 minutes after discontinuing the infusions. As expected, blood loss into the surgical wound was substantial in nine animals receiving therapy initiated before restoring flow in the operated vessel (mean 95 mL, range 45 to 130 mL). By contrast, beginning D-FPRCH2Cl therapy in five animals 15 minutes after restoring arterial flow, a time when surgical hemostasis had been achieved, prevented excessive blood loss (mean 15 mL, range 10 to 35 mL; P < .01 compared with earlier treatment) without compromising the antithrombotic effects. Continuous intravenous infusion of the synthetic antithrombin D-FPRCH2Cl (100 nmol/kg per minute) for 1 hour, beginning immediately after establishing surgical hemostasis, permanently interrupts endarterectomy thrombosis by irreversibly inactivating thrombin bound to the thrombus and retaining already formed hemostatic plugs to prevent surgical bleeding.
|Original language||English (US)|
|Number of pages||9|
|State||Published - 1993|
ASJC Scopus subject areas
- Cell Biology