Effect of sarcopenia in predicting postoperative mortality in emergency laparotomy: a systematic review and meta-analysis

Emergency laparotomy is a time-sensitive procedure with a high mortality range from 8.8 to 18.6% [1‐3], which is much higher than elective surgeries [4‐6]. Elderly patients suffering worse morbidity and mortality following emergency laparotomy have been contributed to multiple medical comorbidities and nutrition status [7]. Effective identification of high-risk patients has been the key to improving perioperative outcomes [5]. However, due to the complexity of the patient's condition, the different variety of surgical types, and the tight operation preparation time, it has been challenging to predict the outcome after emergency surgery based on preoperative information. Several previous studies have used various scoring systems to predict the risk of emergency laparotomy [8, 9]. However, when patients’ condition is too critical to complete functional tests and answer related questions in emergency conditions, the scores are usually subjective and inaccurate [10, 11]. Therefore, it is an urgent requirement to develop a new assessment tool to identify the patient at risk of emergency laparotomy and guide optimal perioperative management [9]. Body composition also plays an important role in predicting treatment outcomes in patients following surgery. Sarcopenia has been observed to be a strong prognostic indicator for perioperative complications [12, 13], including cognitive impairment [14], fractures [15], mental disorders [16], and even survival [17, 18].

Sarcopenia refers to the progressive and global decline in skeletal muscle mass and strength associated with aging, immobility, or illness status [19]. Although there are discrepancies in the diagnostic criteria of sarcopenia in different countries and regions, the cross-sectional area of the lumbar muscle on an abdominal computed tomography (CT) scan is an internationally recognized simple and reliable indicator [20]. It is assessed by measuring muscle mass at the level of the L3 vertebra, which has made a preoperative assessment of psoas major area (PMA) and total skeletal muscle area (SMA) possible based on the routine examination of an abdominal CT scan [21].

Studies have shown that sarcopenia increases the incidence of adverse events and mortality after elective esophageal cancer surgery, gastrectomy, and pancreatic surgery [22‐24]. However, there has been no definite conclusion on the impact of 30-day mortality and postoperative adverse events on emergency laparotomy. Hajibandeh et al. pointed out that sarcopenia can be used to predict mortality in both emergency and elective abdominal surgeries [25]. However, only four studies of emergency surgery were included, so it is unconvincing to draw reliable conclusions. We, therefore, performed further analysis to assess the impact of sarcopenia on 30-day mortality and postoperative complications in patients following emergency laparotomy.

This systematic review and meta-analysis were prepared in accordance with the latest PRISMA requirements and was registered with Prospero (registration number: CRD42022300132) [26]. Two researchers (T.Y. and K.L.) searched databases such as PubMed, Embase, and Cochrane. The search date was as of March 1, 2022. The search was not limited to language and region, and we provided a PRISMA checklist. PubMed's search strategy can be found in Table 1.

Through systematic database searching, we identified 300 articles. After screening to remove duplicate literature, there were 260 articles in total. Thirty-three articles were reviewed for full text following evaluation of the titles and abstracts. Twenty-two articles were excluded due to non-emergency surgery and unclear diagnosis. Review and conference abstract were also excluded in terms of the study design. Overall, 11 articles with 3795 patients were included for further analysis. Fig 1 depicts a flowchart of the study selection process.

Table 2 summarizes the characteristics of the 11 articles that met the inclusion criteria. The total sample size ranged from 80 to 967, all of which were retrospective studies [5, 17, 18, 32‐39]. Of the studies, 10 of them examined muscle mass at the level of the L3 vertebral body on CT scans to diagnose sarcopenia [5, 17, 32‐37, 39] and only one assessed the muscle mass at the level of the L4 vertebral body on CT scans [38].

Emergency laparotomy surgery had high morbidity and mortality. There were few studies investigating the impact of sarcopenia in patients following emergency laparotomy. Our study aimed to assess the risk of death after emergency laparotomy in patients with preoperative sarcopenia. We performed a systematic review and meta-analysis. Eleven eligible studies involving 3795 patients were included. The results showed that sarcopenia was associated with increased postoperative 30-day mortality. There was mild heterogeneity among the nine studies, which were considered high quality. In addition, patients with sarcopenia significantly increased postoperative ICU duration, number of ICU admissions, incidence of postoperative complications.

Patients with preoperative sarcopenia had significantly longer hospital length of stay, but there was large heterogeneity between studies. One of the studies included patients who survived more than or equal to 30 days after surgery in the overall length of stay calculation. The author believed that the impact of early death should be excluded. However, patients that died during the study period were included so as to not overestimate the total duration result. In fact, hospital length of stay in this study was significantly longer than others, which showed that overstated time was a variable of heterogeneity in our study. Considering ICU admissions and hospital length of stay, it was reasonable to presume that patients with sarcopenia following emergency laparotomy were at risk of high medical costs and excessive heavy illness burden.

Our systematic review and meta-analysis independently investigated the association of sarcopenia with prognosis after emergency laparotomy. An efficient and simple assessment tool to identify high-risk surgical patients may be extremely valuable for medical teams’ awareness, especially in time-sensitive situations. Our findings were consistent with previous observative studies confirming that sarcopenia was associated with increased 30-day postoperative mortality in patients undergoing emergency laparotomy [25, 40, 41]. Some studies identified the effect of sarcopenia on mortality and morbidity after elective and emergency abdominal surgeries. However, the quality of evidence is low due to the small number of included studies and participants [25]. In recent years, the impact of sarcopenia on postoperative outcomes has received extensive attention, especially in emergency laparotomy. Therefore, we performed an update of this topic including 11 studies of 3795 patients, and we used the QUIPS and GRADE tools, respectively, to assess the risk of bias and quality of evidence in the included studies. In our study, heterogeneity was low with a dramatically expanded sample size, and the methodological quality of the studies in our review was reliable, increasing the representativeness, and generalizability of our conclusions.

Previous studies found that sarcopenia was associated with multiple adverse outcomes, including falls, functional decline, and postoperative mortality [42]. Sarcopenia was assessed by abdominal computed tomography (CT) L3 pyramid or L4 pyramid total psoas area (TPA) or total psoas index (TPI). TPA < 3.64 cm/m² in women and TPA < 4.55 cm/m² in men or TPI < 1.50 cm/m² in women and TPI < 2.16 cm/m² in men were defined as sarcopenia [43‐46]. Therefore, sarcopenia by abdomen CT scan was used to easily identify the high-risk patients without evaluating them from complicated scales or questionnaires, which is both costly for time and inaccurate in terms of patients’ severeness and degree of cooperation. Meanwhile, most of the patients treated by emergency laparotomy had abdominal CT scan before surgeries. Therefore, sarcopenia was simple, objective, and efficient to be a perioperative risk stratification tool in emergency clinical practice.

The reasons for poor prognosis of patients with sarcopenia after emergency laparotomy were multifactorial, including preoperative frailty, previous malnutrition, and complex comorbidities. In addition, emergency laparotomy surgeries were often insufficiently prepared due to rapid and even life-threatening disease progression. In the postoperative stage, surgical strikes, pain, respiratory failure, circulatory compromise, sepsis, and multiple organ dysfunction also increased the incidence of postoperative complications and mortality.

Although CT-identified sarcopenia can help to predict perioperative risk, we cannot improve patient outcomes through preoperative nutrition and physical activity, as practiced in elective surgery [47]. To these patient groups, we likely pay more attention throughout treatment, such as complications prevention, nutrition intervention in early post-procedure phase, and even immediate intensive care post-surgery. Therefore, preoperative diagnosis of sarcopenia undoubtedly provided important predictive information for general medical management strategies, nursing goals, family awareness, and rehabilitation expectations [48].

There were some limitations in our study. Firstly, the 11 included studies were all retrospective cohort studies. The retrospective design caused them to solely assess muscle mass without measurement of muscle function (grip strength, walking speed, physical activity), which may exaggerate the predictive power of sarcopenia. In our opinion, given that sarcopenia is a serious disease state, we would rather overestimate than underdiagnose. Secondly, there were no clear definition and classification of surgical types in the included literature, so we could not perform subgroup analysis according to surgical procedures specifically, which may have influenced the results of this study. Further research is required to be addressed on specific procedures later. In addition, positive results were more likely to be published and there may be a risk of reporting bias. Most important, in the emergency setting, we have demonstrated that sarcopenia can effectively predict adverse postoperative outcomes.

Recently, some studies argued that patients with sarcopenia cannot be diagnosed by preoperative CT efficiently because of the costs, radiations, and body position restrictions. The point-of-care ultrasound had the advantages of high operability, repeatability, and convenient portability (49). Therefore, point-of-care ultrasound instead of CT scan may be a future research direction to assess the feasibility of sarcopenia diagnosis before emergency surgeries. Exploration of randomized controlled trials is also needed if early targeted interventions on sarcopenia can improve patient outcomes based on our prediction findings.

We found that preoperative CT scan-derived sarcopenia was associated with increased postoperative 30-day mortality and ICU admissions. ICU and hospital length of stay and incidence of postoperative adverse events were also significantly elevated. Further research should demonstrate if dedicated intervention for sarcopenia will improve patient outcomes.