Unit of Cardiothoracic Anaesthesia and Intensive Care, Azienda Ospedaliera Universitaria Senese, Siena, Italy.
BMC Med Inform Decis Mak. 2011 Jun 21;11:44. doi: 10.1186/1472-6947-11-44.
Patients undergoing heart surgery continue to be the largest demand on blood transfusions. The need for transfusion is based on the risk of complications due to poor cell oxygenation, however large transfusions are associated with increased morbidity and risk of mortality in heart surgery patients. The aim of this study was to identify preoperative and intraoperative risk factors for transfusion and create a reliable model for planning transfusion quantities in heart surgery procedures.
We performed an observational study on 3315 consecutive patients who underwent cardiac surgery between January 2000 and December 2007. To estimate the number of packs of red blood cells (PRBC) transfused during heart surgery, we developed a multivariate regression model with discrete coefficients by selecting dummy variables as regressors in a stepwise manner. Model performance was assessed statistically by splitting cases into training and testing sets of the same size, and clinically by investigating the clinical course details of about one quarter of the patients in whom the difference between model estimates and actual number of PRBC transfused was higher than the root mean squared error.
Ten preoperative and intraoperative dichotomous variables were entered in the model. Approximating the regression coefficients to the nearest half unit, each dummy regressor equal to one gave a number of half PRBC. The model assigned 4 units for kidney failure requiring preoperative dialysis, 2.5 units for cardiogenic shock, 2 units for minimum hematocrit at cardiopulmonary bypass less than or equal to 20%, 1.5 units for emergency operation, 1 unit for preoperative hematocrit less than or equal to 40%, cardiopulmonary bypass time greater than 130 minutes and type of surgery different from isolated artery bypass grafting, and 0.5 units for urgent operation, age over 70 years and systemic arterial hypertension.
The regression model proved reliable for quantitative planning of number of PRBC in patients undergoing heart surgery. Besides enabling more rational resource allocation of costly blood-conservation strategies and blood bank resources, the results indicated a strong association between some essential postoperative variables and differences between the model estimate and the actual number of packs transfused.
接受心脏手术的患者仍然是输血需求最大的人群。输血的需求基于因细胞氧合不良而导致并发症的风险，但大量输血与心脏手术患者的发病率增加和死亡率风险增加有关。本研究的目的是确定心脏手术中术前和术中输血的危险因素，并为心脏手术中输血数量的计划制定可靠的模型。
我们对 2000 年 1 月至 2007 年 12 月期间连续接受心脏手术的 3315 例患者进行了一项观察性研究。为了估计心脏手术期间输注的红细胞单位数（PRBC），我们通过逐步选择哑变量作为回归量，开发了一个具有离散系数的多元回归模型。通过将病例分为大小相同的训练集和测试集，从统计学上评估模型性能，并通过调查大约四分之一患者的临床过程细节，这些患者的模型估计值与实际输注的 PRBC 单位数之间的差异高于均方根误差，从临床角度评估模型性能。
该模型纳入了 10 个术前和术中的二项变量。将回归系数近似到最接近的半单位，每个等于 1 的哑回归量给出了半 PRBC 的数量。该模型为术前需要透析的肾衰竭分配 4 个单位，为心源性休克分配 2.5 个单位，为体外循环时最低血细胞比容等于或小于 20%分配 2 个单位，为急诊手术分配 1 个单位，为术前血细胞比容等于或小于 40%分配 1 个单位，为体外循环时间大于 130 分钟和手术类型不同于单纯动脉旁路移植术分配 1 个单位，为紧急手术分配 0.5 个单位，为年龄大于 70 岁和全身性高血压分配 0.5 个单位。
该回归模型被证明可用于心脏手术患者 PRBC 数量的定量计划，除了能够更合理地分配昂贵的血液保存策略和血库资源外，结果还表明一些基本的术后变量与模型估计值和实际输注的 PRBC 单位数之间的差异之间存在很强的关联。
