Hospital costs associated with intraoperative hypotension among non-cardiac surgical patients in the US: a simulation model

Objective: Recent studies indicate intraoperative hypotension, common in non-cardiac surgical patients, is associated with myocardial injury, acute kidney injury, and mortality. This study extends on these findings by quantifying the association between intraoperative hypotension and hospital expenditures in the US. Methods: Monte Carlo simulations (10,000 trial per simulation) based on current epidemiological and cost outcomes literature were developed for both acute kidney injury (AKI) and myocardial injury in non-cardiac surgery (MINS). For AKI, three models with different epidemiological assumptions (two models based on observational studies and one model based on a randomized control trial [RCT]) estimate the marginal probability of AKI conditional on intraoperative hypotension status. Similar models are also developed for MINS (except for the RCT case). Marginal probabilities of AKI and MINS sequelae (myocardial infarction, congestive heart failure, stroke, cardiac catheterization, and percutaneous coronary intervention) are multiplied by marginal cost estimates for each outcome to evaluate costs associated with intraoperative hypotension. Results: The unadjusted (adjusted) model found hypotension control lowers the absolute probability of AKI by 2.2% (0.7%). Multiplying these probabilities by the marginal cost of AKI, the unadjusted (adjusted) AKI model estimated a cost reduction of $272 [95% CI = $223–$321] ($86 [95% CI = $47–$127]) per patient. The AKI model based on relative risks from the RCT had a mean cost reduction estimate of $281 (95% CI = –$346–$750). The unadjusted (adjusted) MINS model yielded a cost reduction of $186 [95% CI = $73–$393] ($33 [95% CI = $10–$77]) per patient. Conclusions: The model results suggest improved intraoperative hypotension control in a hospital with an annual volume of 10,000 non-cardiac surgical patients is associated with mean cost reductions ranging from $1.2–$4.6 million per year. Since the magnitude of the RCT mean estimate is similar to the unadjusted observational model, the institutional costs are likely at the upper end of this range.

研究目标：近期研究显示，非心脏手术患者中普遍存在的术中低血压（intraoperative hypotension）与心肌损伤、急性肾损伤及死亡风险存在相关性。本研究拓展了前述研究成果，量化分析美国人群中术中低血压与住院医疗支出之间的关联。

研究方法：本研究基于当前流行病学及医疗成本结局相关文献，针对非心脏手术患者的急性肾损伤（acute kidney injury, AKI）与非心脏手术心肌损伤（myocardial injury in non-cardiac surgery, MINS）两类病症，构建了蒙特卡洛模拟（Monte Carlo simulations，单次模拟包含10000次试验）框架。针对AKI，构建了3种采用不同流行病学假设的模型：2项基于观察性研究的模型，以及1项基于随机对照试验（randomized control trial, RCT）的模型，用于估算术中低血压状态下AKI发生的边际概率。针对MINS，同样构建了类似模型（不含基于RCT的模型）。将AKI与MINS相关后遗症（心肌梗死、充血性心力衰竭、脑卒中、心脏导管术及经皮冠状动脉介入治疗）的边际概率，与各后遗症对应的边际成本估算值相乘，以此评估术中低血压相关的医疗成本。

研究结果：未校正（校正后）模型显示，优化低血压管控可使AKI的绝对发生概率降低2.2%（0.7%）。将该概率与AKI的边际医疗成本相乘后，未校正（校正后）AKI模型估算得出，每位患者可减少医疗支出272美元[95%置信区间（confidence interval, CI）：223–321美元]（86美元[95%置信区间：47–127美元]）。基于RCT相对风险构建的AKI模型，其平均成本降低估算值为281美元（95%置信区间：–346–750美元）。未校正（校正后）MINS模型则显示，每位患者可减少医疗支出186美元[95%置信区间：73–393美元]（33美元[95%置信区间：10–77美元]）。

研究结论：模型结果表明，对于每年接收10000例非心脏手术患者的医疗机构而言，优化术中低血压管控可实现年均120万至460万美元的医疗成本节约。由于基于RCT的平均估算值与未校正观察性模型的结果相近，该机构的实际成本节约额大概率处于该区间的上限。