Intra-abdominal infection is a common etiology of sepsis, and older patients with intra-abdominal sepsis have a high mortality rate. Therefore, it is significant to evaluate the prognosis accurately. Currently, the measurement of skeletal muscle mass derived from computed tomography (CT) has become a research hotspot. Whereas the prognostic value of skeletal muscle mass in older patients with abdominal sepsis is rarely reported.

To investigate the prognostic value of the skeletal muscle index (SMI) at the midpoint of the third lumbar vertebra (L3) along with Sequential Organ Failure Assessment (SOFA) score or Acute Physiology and Chronic Health EvaluationⅡ (APACHEⅡ) score in older patients diagnosed with intra-abdominal sepsis.

This study was conducted at the Emergency Medicine Clinical Research Center, Beijing Chao-Yang Hospital, Capital Medical University from January 1 to July 31, 2022. A total of 335 older patients with intra-abdominal sepsis were recruited. The participants were divided into survival group (250 cases) and non-survival group (85 cases) based on their survival status during hospitalization. Clinical characteristics and L3 SMI derived from abdominal CT were compared between survival and non-survival groups. Multivariable Logistic regression analysis was used to identify the risk factors of in-hospital mortality in older patients with intra-abdominal sepsis. The receiver operating characteristic (ROC) curves of L3 SMI, SOFA score, APACHEⅡ score, and combined variables for predicting in-hospital mortality were drawn, and the area under the curve (AUC) were calculated and subsequently compared.

335 older patients with intra-abdominal sepsis were included, of whom 85 (25.4%) died. There were statistically significant differences in age, BMI, albumin, creatinine, procalcitonin, L3 SMI, Nutritional Risk Screening 2002 (NRS2002), sepsis shock proportion, SOFA score, APACHE Ⅱ score between the two groups (P<0.05). Multivariable Logistic regression analysis revealed that decreased L3 SMI (OR=0.924, 95%CI=0.886-0.964, P<0.001), increased NRS2002 score (OR=1.312, 95%CI=1.086-1.585, P=0.005), increased SOFA score (OR=1.170, 95%CI=1.053-1.300, P=0.004), and increased APACHEⅡ score (OR=1.052, 95%CI=1.003-1.103, P=0.038) were independent risk factors for in-hospital mortality in older patients with intra-abdominal sepsis. The AUCs of L3 SMI, SOFA score, and APACHEⅡ score for predicting the risk of in-hospital mortality were 0.711, 0.740, and 0.742, respectively. L3 SMI combined with SOFA score, or APACHEⅡ score could improve their predictive ability, with AUCs of 0.795 and 0.792, respectively.

Decreased L3 SMI was an independent risk factor for in-hospital mortality in older patients with intra-abdominal sepsis, The skeletal muscle mass based on abdominal CT combined with critical illness scoring systems could effectively evaluate the prognosis of these patients.

腹腔感染是引起脓毒症的常见病因，老年腹腔脓毒症患者死亡率高，正确评估其预后具有重要意义。目前基于计算机断层扫描（CT）评估骨骼肌量成为研究热点，但骨骼肌量对老年腹腔脓毒症患者预后的预测价值鲜见报道。

探讨第3腰椎（L3）中点平面骨骼肌指数（SMI）联合序贯器官衰竭评估（SOFA）评分、急性生理与慢性健康评分Ⅱ（APACHE Ⅱ）评分对老年腹腔脓毒症患者院内死亡的预测价值。

选取2022-01-01—07-31就诊于首都医科大学附属北京朝阳医院急诊医学临床研究中心的老年腹腔脓毒症患者335例为研究对象。依据患者住院期间是否存活分为生存组（250例）与死亡组（85例），比较两组的临床资料及基于腹部CT的L3 SMI水平。利用多因素Logistic回归分析探究老年腹腔脓毒症患者院内死亡的影响因素。分别绘制L3 SMI、SOFA评分、APACHE Ⅱ评分及联合指标预测患者院内死亡风险的受试者工作特征（ROC）曲线，计算曲线下面积（AUC）并进行比较。

335例老年腹腔脓毒症患者的院内病死率为25.4%（85/335）。两组患者年龄、BMI、白蛋白、肌酐、降钙素原、L3 SMI、营养风险筛查2002（NRS2002）、脓毒性休克占比、SOFA评分、APACHE Ⅱ评分比较，差异有统计学意义（P<0.05）。多因素Logistic回归分析结果显示，低L3 SMI（OR=0.924，95%CI=0.886~0.964，P<0.001）、高NRS2002评分（OR=1.312，95%CI=1.086~1.585，P=0.005）、高SOFA评分（OR=1.170，95%CI=1.053~1.300，P=0.004）、高APACHE Ⅱ评分（OR=1.052，95%CI=1.003~1.103，P=0.038）是老年腹腔脓毒症患者院内死亡的独立危险因素。L3 SMI、SOFA评分、APACHE Ⅱ评分预测患者院内死亡风险的AUC分别为0.711、0.740、0.742。L3 SMI联合SOFA评分或APACHE Ⅱ评分将提高其预测效能，AUC分别为0.795、0.792。

低L3 SMI是老年腹腔脓毒症患者院内死亡的独立危险因素，基于腹部CT的骨骼肌量联合危重症评分系统可有效评估其预后。