Aylsworth Christopher L, Stefan Faith, Woitas Karl, Rieger Randall H, LeBoutillier Martin, DiSesa Verdi J
The CardioVascular Center at The Chester County Hospital, West Chester, Pennsylvania, USA.
Ann Thorac Surg. 2004 Mar;77(3):973-6. doi: 10.1016/S0003-4975(03)01660-6.
Accurate control of the anticoagulation level is important for safe initiation of cardiopulmonary bypass. Using the Hemochron Jr., we consistently noted a higher than customary heparin dose required to achieve an activated clotting time (ACT) that, according to the literature and our quality standards, should be more than 480 seconds. This study was designed to determine whether there existed a significant difference in ACT values measured by the newer Hemochron Jr. and the older Hemochron 801 assay system.
A total of 30 patients underwent cardiovascular surgical procedures requiring heparinization (300 U/kg). Multiple samples for measurement of the ACT were obtained from all patients before heparinization, after heparinization, during cardiopulmonary bypass, and after protamine administration. Arterial samples were collected, and ACT was determined simultaneously on the same sample using both Hemochron Jr. and Hemochron 801. Activated clotting time data were analyzed with a linear mixed model using an unstructured variance-covariance matrix.
Descriptive statistics on all heparinized patients revealed that the Hemochron Jr. yielded ACT results that on average were 121.28 seconds lower than the determination by the standard Hemochron 801 on the same sample of blood. This difference was -139.04 in on-pump cases and -90.51 in off-pump cases, primarily a function of the fact that higher heparin doses and therefore longer ACTs were used in patients having operations using the heart-lung machine. From the linear mixed model, the estimated average paired difference between the Hemochron Jr. and Hemochron 801 was found to be -86.03, yielding a highly significant test statistic (t(28) = -6.18; p < 0.0001).
Lower ACT values determined by Hemochron Jr. are consistent with higher, clinically acceptable ACT values as measured by the Hemochron 801. These findings would suggest that safe levels of anticoagulation are determined in part by the specific assay used.
准确控制抗凝水平对于安全启动体外循环至关重要。使用Hemochron Jr.时，我们一直注意到，要达到活化凝血时间（ACT）（根据文献和我们的质量标准，该时间应超过480秒），所需的肝素剂量高于常规剂量。本研究旨在确定新型Hemochron Jr.与旧型Hemochron 801检测系统所测ACT值之间是否存在显著差异。
共有30例患者接受了需要肝素化（300 U/kg）的心血管外科手术。在肝素化前、肝素化后、体外循环期间以及鱼精蛋白给药后，从所有患者身上采集多个用于测量ACT的样本。采集动脉样本，并使用Hemochron Jr.和Hemochron 801在同一样本上同时测定ACT。使用非结构化方差 - 协方差矩阵的线性混合模型分析活化凝血时间数据。
对所有肝素化患者的描述性统计显示，Hemochron Jr.得出的ACT结果平均比标准Hemochron 801对同一份血样的测定结果低121.28秒。在体外循环病例中，这一差异为 -139.04，在非体外循环病例中为 -90.51，这主要是因为在使用心肺机进行手术的患者中使用了更高的肝素剂量，因此ACT更长。从线性混合模型中发现，Hemochron Jr.与Hemochron 801之间估计的平均配对差异为 -86.03，产生了高度显著的检验统计量（t(28) = -6.18；p < 0.0001）。
Hemochron Jr.测定的较低ACT值与Hemochron 801测定的较高且临床可接受的ACT值一致。这些发现表明，抗凝的安全水平部分取决于所使用的特定检测方法。
