Toronto General Hospital, 200 Elizabeth St., 3EN-402 Toronto, ON, Canada M5G 2C4.
Anesth Analg. 2010 Aug;111(2):331-8. doi: 10.1213/ANE.0b013e3181e456c1. Epub 2010 Jul 7.
Accurate risk stratification may help reduce the burden of excessive blood loss after cardiac surgery. We measured the incremental value of thrombelastography to an existing risk prediction model for excessive blood loss in cardiac surgery.
This observational study included 434 patients who underwent cardiac surgery with cardiopulmonary bypass (CPB) and had thrombelastographic measures before and during CPB, their risk of excessive blood loss could be calculated with an existing risk prediction model and they had not received clopidogrel or warfarin within 5 days of surgery. Excessive blood loss was defined as transfusion of > or = 5 U of red blood cells from termination of CPB to 1 day after surgery. Logistic regression models including an existing risk prediction model without and with thrombelastographic measures were constructed. Improvement in risk prediction was measured by the area under the curve and net reclassification improvement.
Excessive blood loss occurred in 59 of 434 patients (13.6%). The only thrombelastographic measure that improved risk stratification was maximum amplitude during CPB, which reflects maximum clot strength. Although the addition of this variable to the existing prediction model did not have a material effect on the area under the curve (increased from 0.780 to 0.784; P = 0.8), it did improve the net reclassification improvement by 12% (P = 0.05), primarily by improving the detection of high-risk cases.
Risk stratification for excessive blood loss after cardiac surgery is improved when on-CPB thrombelastography is added to an existing risk prediction model that incorporates readily available patient- and surgery-related variables, but large, multicenter trials are needed to verify this finding and create a new risk prediction model.
准确的风险分层有助于减少心脏手术后过度失血的负担。我们测量了血栓弹力描记术对心脏手术后过度失血的现有风险预测模型的增量价值。
本观察性研究纳入了 434 名接受体外循环（CPB）心脏手术的患者，在 CPB 前和 CPB 期间进行了血栓弹力描记术测量，他们的过度失血风险可以用现有的风险预测模型计算，并且在手术前 5 天内没有接受氯吡格雷或华法林治疗。过度失血定义为从 CPB 结束到手术后 1 天输注 >或= 5 U 红细胞。构建了包含现有风险预测模型而不包含和包含血栓弹力描记术测量值的逻辑回归模型。通过曲线下面积和净重新分类改善来衡量风险预测的改善。
434 例患者中 59 例（13.6%）发生过度失血。唯一改善风险分层的血栓弹力描记术测量值是 CPB 期间的最大振幅，反映了最大血凝块强度。尽管将该变量添加到现有预测模型中对曲线下面积没有实质性影响（从 0.780 增加到 0.784；P = 0.8），但它确实将净重新分类改善提高了 12%（P = 0.05），主要是通过提高高危病例的检测能力。
当在包含容易获得的患者和手术相关变量的现有风险预测模型中添加 CPB 期间的血栓弹力描记术时，心脏手术后过度失血的风险分层得到改善，但需要进行大型、多中心试验来验证这一发现并创建新的风险预测模型。
