Sepsis in the health care field has remained a problematic subject in general health services, as its mortality rate is high, ranging from 20–50% 21–23. Hepatic failure is a component of MODS in sepsis and is often associated with a poor prognosis, although its exact incidence is unknown24, 25. Damaged liver can contribute to the development and spread of multiple organ failure26.
The results of our research reported a morbidity rate of 7.91% (1039 of 12129 patients) and mortality rate of 44.10% (458 of 1039 patients) in patients with SALI, suggesting a lower incidence and higher death rate than the Liu Y et al.15 and Kobashi et al.26 clinical reports. We found that Liu Y's team used the older data version 1.0 of MIMIC-IV, which only included liver function indicators in the SALI diagnostic criteria and did not include the more novel combined liver function and coagulation criteria, while that allowed the inclusion of SALI diagnosed any time within 48 hours of hospitalization, but our study only included the first 24 hours of ICU MIMIC-IV in version 2.0. Therefore, we hypothesized that these differences resulted in a lower patient rate but a higher mortality rate than the study by Liu Y's team. Again, in the 2013 investigation by Professor Kobashi, a wider scale of sepsis 2.0 criteria was used, and the standards for inclusion in the SALI group only covered liver function, without coagulation. The standards failed to assess more comprehensively the outcome of the inherent injury and the subsequent injury caused by SALI and therefore also reached the same conclusion as Liu Y's team. However, these teams are all aware that a tool is not enough to predict prognosis in sepsis patients and liver injury patients, consistent with our idea.
In this article, the 10 indicators are age, the use of vasopressors, mean arterial pressure, mean SpO2, lactate maximum, BUN maximum, TBIL maximum, albumin minimum, RDW maximum and APTT maximum, from which we found that the BUN maximum has the largest weight. In accordance with its contribution to the nomogram, BUN level was the maximum factor of 90-day mortality in SALI patients. BUN levels are strongly correlated with mortality in patients with sepsis, and sepsis patients have a higher rate of death when their BUN levels increase 27–30. A large study30 found that this association disappeared at the 41.1 mg/dL turning point. For every 10 mg/dL increase in BUN level, sepsis patients had a 29.8% increase in 30-day mortality, while patients with a BUN level ≥ 41.1 mg/dL experienced only a 4.5% increase in 30-day mortality. The BUN level can be utilized as an easy-to-use and rapid measure for early identification in sepsis patients because early and effective management is crucial in this condition. In a study of 2917 patients with sepsis, BUN level (1.08 [1.07–1.09]) was a strong factor of the incidence of AKI with sepsis, and the most sensitive indicator of AKI occurrence was BUN level31. Although the mechanism by which elevated BUN levels can contribute to the poor prognosis associated with sepsis is not clearly defined, there are still several possible reasons that can be explained. Patients in the severe stage are in a hyperproteolytic metabolic state32, and BUN levels increase when protein is excessively catabolic or the renal filtration rate is reduced. Therefore, BUN levels can play an important role in body protein catabolism33 and are a sign of renal damage. The rate of protein catabolism is significantly increased in sepsis patients34, and sepsis is usually accompanied by acute kidney injury35. These factors can contribute to elevated BUN levels in patients with sepsis. The BUN level is more widely used in sepsis and other areas of sepsis and is being used for the first time in patients with SALI and was first reported in adult SALI patients in our study.
There are several other variables in the nomogram that play an important role. A cohort study showed that age was an independent factor in the incidence of SALI patients. Among subjects not over 39 years old, the proportions of "cholestatic", "hepatocellular", and "shock liver" disease were 22.2%, 66.6%, and 11.1%, respectively. Additionally, among subjects who were at or over 40 years of age, these percentages were 51.5%, 15.9%, and 32.6%, respectively26. In a recent study, a scholar referred to age as an important component of mortality involved in SALI patients15. With the increasing severity of sepsis disease, a large proportion of patients have circulatory instability and require ascending agents to maintain hemodynamic stability36–38, yet the inclusion of vasopressors and mean arterial pressure were first reported in sepsis-associated liver injury in our study. Blood lactate, an indicator of tissue perfusion, is often used to provide feedback on survival in patients with sepsis39, 40, and some high-quality studies on the effect of lactate on mortality in SALI patients have been identified only in children41, 42; this is the first report in adult SALI patients. Some of the other variables, such as TBIL, albumin, RDW and APTT, which are frequently used in research to predict sepsis and sepsis-associated injury14, 17, 18, 43, 44, are rarely mentioned in studies of sepsis-associated liver injury, especially in adult reports15. Our findings suggest that all of these variables independently predict mortality from sepsis-associated liver injury.
Initially, clinical prediction models were used for oncology patients45–47, and as an increasing number of researchers continue to develop their understanding of clinical prediction models, they are commonly used in critical illness48, 49. There is no authoritative standard for the prognostic assessment of patients with sepsis-associated liver injury to date, and there are few large data studies with a very strong evidence-based medical basis. Our study contains a visual nomogram based on 10 clinically readily available and commonly used parameters that were extracted from a large database called MIMIC-IV, and the efficiency of the current nomogram underwent thorough comprehensive evaluation and internal validation.
Professor Fragaki stated that the ALBI score is more appropriate for the identification and prognostic evaluation of early-onset liver dysfunction in a recent study 50; therefore, we chose the ALBI score to assess liver function in this article. The SOFA score, LODS score and SAPS II score are widely used in mortality risk analysis and prognosis assessment of patients with sepsis17, 44, 51, 52. It is rare to use a model to predict both sepsis and liver injury at the same time, except in the few reports where the level of evidence is not high15. Nevertheless, the validity of these scores in prescribing the risk of 90-day mortality in SALI patients still remains unknown. To compare these scores, we evaluated the hypothesized nomogram's predictive accuracy with various widely used clinical scores, including the SOFA, LODS, SAPS II, and ALBI scores, based on the AUROC. The nomogram performed best in all of the tools. The result that the nomogram could successfully distinguish between true positive patients at high risk of 90-day mortality in both the training and validation sets was further evidenced by DCA curves, IDI, and NRI indices. The nomogram in this case performed better in differentiating the risk of 90-day mortality, as supported by the high C-index (0.778) in the training set and the C-index (0.804) in the validation set, as well as by acceptable calibration. By developing the scale score, the change in each variable is described from the forest plot, and then the total score is computed to predict the possibility that an event will occur.
Several limitations include the following: 1) There is a lack of a definitive definition of SALI. 2) The confounding factors can occur with the inclusion of each variable, which can affect the results because this study is retrospective. 3) According to the definition of sepsis, the addition of specific pathogenic culture results might have improved the predictive strength of the model. Our study only contains parameters related to the first day in the ICU, and it might have been better to have dynamic, continuous observational analysis data on indicators during the ICU stay. 4) When we imported data from the MIMIC-IV database, we found that many variables were missing, and even some missing data were greater than 50%, and these parameters might have an impact on our findings. 5) The MIMIC-IV database is only a single-center study. In the future, multicenter research can be performed in different countries and regions with different economic levels, and external databases can be used for validation. These are endeavors we will pursue in the future.