目的

探讨术前身体质量指数（Body mass index, BMI）与择期非心脏手术老年患者全身麻醉诱导后低血压（Post-induction hypotension, PIH）之间的关联。

方法

本研究为单中心回顾性队列研究，最终纳入了2013年1月1日至2022年12月31日期间在北京协和医院接受全麻择期非心脏手术的60岁及以上老年患者，共70487例。主要研究结局为PIH，定义为诱导后时间段内收缩压<90 mmHg，或较基线收缩压下降>30%。采用多因素Logistic回归分析的限制性立方样条（Restricted cubic spline, RCS）评估BMI与PIH之间的非线性关系。次要结局包括ICU转入、住院时间及住院期间死亡。

结果

PIH的总体发生率为73.3%（n = 51700）。BMI与PIH之间呈U型非线性关系，拐点出现在26.2 kg/m²（95% CI: 26.1-26.4 kg/m²），这种非线性关系也在PIH的多个维度上被观察到。本研究在该U型曲线上进一步发现了一个“低风险”BMI区间，即超重至轻度肥胖区间（24.2-29.7 kg/m²）。BMI低于此区间的老年患者发生PIH的风险显著升高（OR = 1.13, 95% CI: 1.09-1.17, P < 0.001），术后转入ICU风险增加（OR = 1.31, 95% CI: 1.24-1.39, P < 0.001），住院时间延长（IRR = 1.08, 95% CI: 1.06-1.10, P < 0.001）。相反，BMI高于“低风险”区间的患者，仅ICU转入风险增加（OR = 1.21, 95% CI: 1.08-1.36, P = 0.001），但PIH风险（OR = 1.05, 95% CI: 0.98-1.13, P = 0.169）及住院时间（IRR = 0.99, 95% CI: 0.95-1.02, P = 0.415）未增加。BMI与住院期间死亡并无显著关联（P_overall = 0.480, P_nonlinear = 0.483）。

结论

本项回顾性队列研究发现，在接受择期非心脏手术的老年患者中，术前BMI与PIH之间存在U型的非线性关系，将BMI控制在24.2-29.7 kg/m²的范围内可能有助于降低PIH风险并改善术后结局。BMI作为老年患者术前强化干预中的可优化因素，应与其他临床因素一起，成为评估围手术期风险的重要参考指标，以期更好地指导术前准备并改善患者预后。

Objective

To explore the association between body mass index (BMI) and post-induction hypotension (PIH) in elderly patients undergoing elective non-cardiac surgery.

Methods

In this retrospective cohort study, a total of 70 487 elderly patients aged 60 years and older undergoing elective non-cardiac surgery between January 1, 2013, and December 31, 2022 were included in the final analysis. The primary outcome is PIH, defined as a systolic blood pressure (SBP) < 90 mmHg or a decrease of > 30% from baseline SBP during the post-induction period. Restricted cubic spline (RCS) curve was displayed to assess the non-linear relationship between BMI and PIH with multivariate logistic regression. Secondary outcomes include ICU admission, length of hospital stay, and in-hospital mortality.

Results

Of the 70 487 elderly patients undergoing elective non-cardiac surgery, the overall incidence of PIH was 73.3% (n = 51 700). There was a U-shaped association between BMI and PIH, with a change point at 26.2 kg/m² (95% CI, 26.1-26.4 kg/m²). This kind of non-linear relationship was also observed in multiple dimensions of PIH. This U-shaped curve further revealed a low-risk BMI range for overweight and mild obesity (24.2-29.7 kg/m²). Elderly patients with BMI below this range had a significantly higher risk of PIH (OR = 1.13, 95% CI: 1.09-1.17, P < 0.001), higher risk of ICU admission (OR = 1.31, 95% CI: 1.24-1.39, P < 0.001) and longer hospital stay (IRR = 1.08, 95% CI: 1.06-1.10, P < 0.001). Nevertheless, BMI above the low-risk range only elevate the risk of ICU admission (OR = 1.21, 95% CI: 1.08-1.36, P = 0.001), but neither PIH (OR = 1.05, 95% CI: 0.98-1.13, P = 0.169) nor length of hospital stay (IRR = 0.99, 95% CI: 0.95-1.02, P = 0.415). There was no non-linear relationship between BMI and in-hospital mortality (P_overall = 0.480, P_nonlinear = 0.483).

Conclusions

This retrospective cohort study suggested a U-shaped non-linear relationship between BMI and PIH in elderly patients undergoing elective non-cardiac surgery. Maintaining BMI within the range of 24.2-29.7 kg/m² may reduce PIH risk and improve surgical outcomes. Preoperative BMI screening may help identify vulnerable patients in need of optimisation.