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

<b>Objective:</b> 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. <b>Methods:</b> 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. <b>Results:</b> 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. <b>Conclusions:</b> 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：** 近期研究表明，在非心脏手术患者中较为常见的术中低血压（intraoperative hypotension）与心肌损伤、急性肾损伤（acute kidney injury, AKI）及死亡率存在关联。本研究在此前研究基础上，量化了美国人群中术中低血压与住院支出之间的关联。
**研究方法：** 本研究基于当前流行病学与成本结局相关文献，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）构建了蒙特卡洛模拟（Monte Carlo simulations）模型，每次模拟包含10000次试验。针对AKI，我们构建了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与1项基于随机对照试验（randomized control trial, RCT）的模型，用于估算基于术中低血压状态的AKI边际发生概率。针对MINS，我们同样构建了类似模型（仅不含基于RCT的模型）。将AKI与MINS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）的边际发生概率，与各结局对应的边际成本估算值相乘，以此评估术中低血压相关的住院成本。
**研究结果：** 未校正（校正）模型显示，低血压管控可使AKI的绝对发生概率降低2.2%（0.7%）。将上述概率与AKI的边际成本相乘后，未校正（校正）AKI模型估算得到每位患者可减少住院支出272美元[95%置信区间（confidence interval, CI）：223~321美元]（86美元[95%CI：47~127美元]）。基于RCT相对风险构建的AKI模型，其平均成本减少估算值为281美元（95%CI：-346~750美元）。未校正（校正）MINS模型则估算得到每位患者可减少住院支出186美元[95%CI：73~393美元]（33美元[95%CI：10~77美元]）。
**研究结论：** 模型结果显示，对于每年收治10000例非心脏手术患者的医院而言，优化术中低血压管控策略可使年平均住院支出减少120万~460万美元。由于基于RCT的平均估算值与未校正观察性研究模型的结果相近，因此该医院的实际成本节约额大概率处于该区间的上限。