Hughes Steven D, Bishop Paul D, Garcia Richard, Zhang Tracy, Alexander W Allan
ZymoGenetics, Inc Seattle, WA, USA.
Ann Surg Innov Res. 2009 Nov 19;3:14. doi: 10.1186/1750-1164-3-14.
This study was designed to evaluate the effect of recombinant human thrombin (rThrombin) concentration on time to hemostasis (TTH), clot durability, and clot strength in settings that replicate the heparinization and platelet inhibition often found in surgical populations.
A modified, anticoagulated rabbit arteriovenous shunt preparation was selected to model vascular anastomotic bleeding. Rabbits were treated with heparin or heparin + clopidogrel and TTH was measured after applying a range of topical rThrombin concentrations or placebo, in combination with absorbable gelatin sponge, USP. Treatments (placebo, rThrombin) were randomly assigned and the investigator was blinded to treatment. TTH was evaluated with the Kaplan-Meier method. After hemostasis was achieved, clot burst assessment was performed for heparin + clopidogrel treated animals. Clot viscoelastic strength and kinetics were measured in ex-vivo samples using thromboelastography (TEG) methods.
TTH decreased with increasing concentrations of rThrombin in heparin-treated animals and was shorter after treatment with 1000 IU/mL rThrombin (73 seconds) than with 125 IU/mL rThrombin (78 seconds; p = 0.007). TTH also decreased with increasing concentrations of rThrombin in heparin + clopidogrel treated animals; again it was significantly shorter after treatment with 1000 IU/mL rThrombin (71 seconds) than with 125 IU/mL rThrombin (177 seconds; p < 0.001). Variability in TTH was significantly smaller after treatment with 1000 IU/mL rThrombin than after 125 IU/mL rThrombin, indicating greater reliability of clot formation (p < 0.001 for heparin or heparin + clopidogrel treatments). Clot durability was examined in heparin + clopidogrel treated animals. Clots formed in the presence of 1000 IU/mL rThrombin were significantly less likely to rupture during clot burst assessment than those formed in the presence of 125 IU/mL rThrombin (0% versus 79%, p < 0.001). In vitro clot strength and clot kinetics, as determined by TEG in heparin + clopidogrel samples, were positively associated with the amount of rThrombin activity added for clot initiation.
In an animal model designed to replicate the anti-coagulation regimens encountered in clinical settings, topical rThrombin at 1000 IU/mL more reliably controlled the pharmacological effects of heparin or heparin + clopidogrel on hemostasis than rThrombin at 125 IU/mL. Results from in vitro assessments confirmed a positive relationship between the amount of rThrombin activity and both the rate of clot formation and clot strength.
本研究旨在评估重组人凝血酶（rThrombin）浓度对止血时间（TTH）、血凝块耐久性和血凝块强度的影响，研究环境模拟了手术人群中常见的肝素化和血小板抑制情况。
选择一种改良的、抗凝的兔动静脉分流制备方法来模拟血管吻合口出血。给兔子使用肝素或肝素+氯吡格雷进行治疗，在应用一系列局部rThrombin浓度或安慰剂，并联合使用美国药典规定的可吸收明胶海绵后，测量TTH。治疗方法（安慰剂、rThrombin）随机分配，研究人员对治疗情况不知情。采用Kaplan-Meier方法评估TTH。止血完成后，对接受肝素+氯吡格雷治疗的动物进行血凝块破裂评估。使用血栓弹力图（TEG）方法在体外样本中测量血凝块粘弹性强度和动力学。
在肝素治疗的动物中，TTH随rThrombin浓度升高而降低，用1000 IU/mL rThrombin治疗后的TTH（73秒）比用125 IU/mL rThrombin治疗后的TTH（78秒）短（p = 0.007）。在肝素+氯吡格雷治疗的动物中，TTH也随rThrombin浓度升高而降低；同样，用1000 IU/mL rThrombin治疗后的TTH（71秒）比用125 IU/mL rThrombin治疗后的TTH（177秒）显著缩短（p < 0.001）。用1000 IU/mL rThrombin治疗后的TTH变异性明显小于用125 IU/mL rThrombin治疗后的变异性，表明血凝块形成的可靠性更高（肝素或肝素+氯吡格雷治疗的p < 0.001）。在接受肝素+氯吡格雷治疗的动物中检查了血凝块耐久性。在血凝块破裂评估期间，在1000 IU/mL rThrombin存在下形成的血凝块破裂的可能性明显低于在125 IU/mL rThrombin存在下形成的血凝块（0%对79%，p < 0.001）。通过TEG测定，肝素+氯吡格雷样本中的体外血凝块强度和血凝块动力学与用于启动血凝块的rThrombin活性量呈正相关。
在一个旨在模拟临床环境中抗凝方案的动物模型中，1000 IU/mL的局部rThrombin比125 IU/mL的rThrombin更可靠地控制肝素或肝素+氯吡格雷对止血的药理作用。体外评估结果证实了rThrombin活性量与血凝块形成速率和血凝块强度之间存在正相关关系。
