Refinements evaluating minimum surgery volume standards

将病人转移到进行最少手术次数的医生那里，作为减少手术死亡的一种方式，越来越受欢迎。但是，外科医生与医院数量的独立影响尚不清楚：在规模小的医院，由规模大的外科医生进行手术更安全，还是在规模大的医院由规模小的外科医生进行手术更安全？“安全区域”对不同手术的外科医生和医院数量的依赖不同吗？分层模型最近被用来估计外科医生和医院数量对手术结果的独立影响。然而，他们可能没有充分考虑到这些因素的内在混淆。我们将使用一种新的方法修改来解决这个问题，重新检查最近一项关于医院和外科医生手术量标准的重要研究的数据。修改是直观的。例如，我们仅通过与同一家医院的外科医生进行比较来研究死亡率作为外科医生数量的函数。在形式上，我们将使用具有医院级固定效应的分层模型。该方法在冠状动脉旁路移植术和选择性腹主动脉瘤修复两种心血管手术中的初步应用表明，纠正这种混淆会导致显著不同的结果。我们已获准使用14项高风险心血管手术和癌症切除的大型分析性医疗保险患者水平结果文件。这些数据使当前的研究能够快速、经济地完成。对于每种手术，我们将报告：i)与外科医生和医院的最小容量标准有关的调查结果，以及ii)通过对医院和/或外科医生实施适当定制的最小容量标准可以实现的手术死亡减少估计。以本研究的结果为指导，我们的长期目标是探索影响手术结果的关键过程差异。

Switching patients to providers who perform a minimum number of surgeries is gaining popularity as a way to reduce operative deaths. But the independent effects of surgeon versus hospital volumes are unclear: is an operation safer in the hands of a high-volume surgeon in a low-volume hospital versus a low-volume surgeon in a high-volume hospital? Does the "safe region" rely differently on surgeon versus hospital volumes for different operations? Hierarchical models have recently been used to estimate the independent effects of surgeon and hospital volumes on surgical outcomes. However, they may not have adequately accounted for the inherent confounding of these factors. We will address this issue using a novel methodological modification to reexamine the data from an important recent study on surgery volume standards for hospitals and surgeons. The modification is intuitive. For example, we examine mortality as a function of surgeon volume only via comparisons with surgeons operating in the same hospital. Formally, we will use a hierarchical model with hospital-level fixed effects. Preliminary application of this approach for two cardiovascular procedures ~ coronary-artery bypass grafting and elective repair of an abdominal aortic aneurysm, indicate that correcting for this confounding leads to significantly different findings. We have permission to use a large, analytic Medicare patient-level outcomes file for 14 high-risk cardiovascular procedures and cancer resections. These data enable rapid and cost-effective completion of the current study. For each procedure we will report: i) findings relating to minimum volume standards for surgeons and hospitals, and ii) estimated reductions in operative deaths that could be achieved by imposing appropriately tailored minimum volume standards for hospitals and/or surgeons. Using the results of the proposed study as a guide, our long-term objective is to explore key process differences that underlie operative outcomes.