Gastrointestinal bleeding (GIB) is a major cause of morbidity and mortality in critically ill patients and remains one of the most frequent emergencies encountered in intensive care units (ICUs). It encompasses bleeding originating from the upper or lower gastrointestinal tract and may present as hematemesis, melena, or hematochezia, often leading to hemodynamic instability and need for urgent intervention [1]. Despite improvements in endoscopic techniques, pharmacological therapy, and critical care support, outcomes remain suboptimal in ICU populations compared to general wards [2].

The incidence of GIB in ICU patients varies widely, with reported rates ranging from 1.5% to 8.5%, depending on patient population and risk profile [3]. Stress-related mucosal disease, coagulopathy, mechanical ventilation, and multi-organ dysfunction contribute significantly to the development of bleeding in critically ill patients [4]. Moreover, ICU patients often have underlying comorbidities such as chronic liver disease, renal failure, and sepsis, which further exacerbate bleeding risk and complicate management [5].

Mortality associated with gastrointestinal bleeding in the general population is estimated at approximately 5–10%; however, in ICU settings, mortality rates are substantially higher, often exceeding 15–25% due to the severity of illness and associated complications [2,6]. This elevated mortality is not solely attributable to bleeding itself but is frequently related to underlying critical illness, delayed intervention, and organ failure [7].

Several clinical and biochemical parameters have been proposed as predictors of mortality in patients with GIB. Advanced age, presence of shock, need for mechanical ventilation, and renal replacement therapy have consistently been associated with poor outcomes [8]. Additionally, severity scoring systems such as the Sequential Organ Failure Assessment (SOFA) and Simplified Acute Physiology Score (SAPS II) have demonstrated strong prognostic value in ICU patients with gastrointestinal bleeding [9]. Laboratory markers, particularly elevated serum lactate levels, have also emerged as important indicators of tissue hypoperfusion and predictors of mortality [10].

Although numerous individual studies have evaluated risk factors and outcomes in gastrointestinal bleeding, most have focused on heterogeneous patient populations or non-ICU settings. There remains a lack of comprehensive synthesis specifically addressing predictors of mortality among ICU patients with GIB. Understanding these predictors is crucial for early risk stratification, guiding clinical decision-making, and improving patient outcomes.

Therefore, the present systematic review and meta-analysis aims to evaluate the outcomes and identify key predictors of mortality in critically ill patients with gastrointestinal bleeding, thereby providing evidence to support improved clinical management and prognostication in ICU settings.

MATERIALS AND METHODS

Study Design and Reporting

This systematic review and meta-analysis was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines [11]. The methodology was predefined to ensure transparency and reproducibility of results.

Search Strategy

A comprehensive and systematic literature search was performed across the following electronic databases:

• PubMed/MEDLINE
• Embase
• Cochrane Library

The search included studies published up to December 2025. The following combination of Medical Subject Headings (MeSH) terms and keywords was used:

“Gastrointestinal bleeding” OR “GI bleeding” AND “intensive care unit” OR “ICU” AND “mortality” OR “outcome” AND “predictors” OR “risk factors”

Additionally, the reference lists of relevant articles were manually screened to identify any additional eligible studies.

Eligibility Criteria

Inclusion Criteria

• Studies involving adult patients (≥18 years) admitted to ICU with gastrointestinal bleeding
• Studies reporting mortality outcomes
• Studies evaluating predictors or risk factors for mortality
• Observational studies (cohort, case-control) and randomized controlled trials
• Full-text articles available in English

Exclusion Criteria

• Pediatric studies
• Case reports, case series (<20 patients), reviews, editorials
• Studies lacking sufficient data on mortality or predictors
• Duplicate publications

Study Selection

All identified studies were imported into reference management software, and duplicates were removed. Two independent reviewers screened titles and abstracts for eligibility. Full texts of potentially relevant studies were then assessed. Disagreements were resolved through discussion or consultation with a third reviewer.

Data Extraction

A standardized data extraction form was used. The following variables were collected:

• Author and year of publication
• Study design and country
• Sample size
• Patient demographics (age, sex)
• Type of gastrointestinal bleeding (upper/lower)
• ICU characteristics
• Mortality outcomes (ICU or in-hospital mortality)
• Predictors of mortality (clinical, laboratory, and scoring systems)

Quality Assessment

The methodological quality of included observational studies was assessed using the Newcastle–Ottawa Scale (NOS) [12]. Studies were evaluated based on:

• Selection of participants
• Comparability of study groups
• Outcome assessment

Studies scoring ≥7 were considered high quality.

Outcome Measures

Primary Outcome

• All-cause mortality (ICU or in-hospital mortality)

Secondary Outcomes

• Identification of predictors of mortality, including:
• Demographic factors (age, sex)
• Clinical variables (shock, comorbidities)
• Organ support (mechanical ventilation, renal replacement therapy)
• Laboratory markers (lactate, hemoglobin)
• Severity scores (SOFA, SAPS II)

Statistical Analysis

Meta-analysis was performed using a random-effects model to account for inter-study variability [13].

• Pooled mortality rates were calculated with 95% confidence intervals (CI)
• Odds ratios (ORs) were used for categorical predictors
• Continuous variables were analyzed using standardized mean differences (SMD)

Heterogeneity was assessed using:

• I² statistic (low <25%, moderate 25–75%, high >75%)
• Chi-square (Q) test

Publication bias was evaluated using funnel plots and Egger’s test where applicable.

Subgroup and Sensitivity Analysis

Where sufficient data were available, subgroup analyses were performed based on:

• Type of bleeding (upper vs lower GI bleeding)
• ICU type (medical vs surgical ICU)
• Geographic region

Sensitivity analysis was conducted by excluding low-quality studies to assess the robustness of pooled estimates.

Ethical Considerations

As this study is a systematic review and meta-analysis of previously published data, ethical approval and informed consent were not required.

RESULTS

A total of 1,245 records were identified through database searching. After removal of duplicates (n = 312), 933 studies were screened based on titles and abstracts. Of these, 74 full-text articles were assessed for eligibility, and finally, 18 studies fulfilling the inclusion criteria were included in the systematic review and meta-analysis. The overall pooled sample comprised approximately 32,000 ICU patients with gastrointestinal bleeding.

Figure 1. PRISMA Flow Diagram of Study Selection; Flow diagram illustrating the process of study selection according to PRISMA guidelines. A total of 1,245 records were identified through database searching. After removal of duplicates (n = 312), 933 records were screened, of which 74 full-text articles were assessed for eligibility. Finally, 18 studies were included in the systematic review and meta-analysis.

The included studies were conducted across multiple geographic regions including Asia, Europe, and North America, with the majority being retrospective or prospective cohort studies. The sample size of individual studies ranged from 1,200 to 4,500 patients. Most studies included mixed ICU populations, while some focused specifically on upper or lower gastrointestinal bleeding.

Table 1: Characteristics of Included Studies

The pooled baseline characteristics demonstrated that the mean age of patients ranged from 58 to 72 years, with a predominance of males (60–68%). A substantial proportion of patients required organ support, reflecting the severity of illness in ICU settings. Mechanical ventilation was required in approximately 35–55% of patients, while 25–40% presented with shock at admission. Renal replacement therapy was needed in 10–22% of cases, and comorbid conditions such as liver disease were present in up to 30% of patients.

Table 2: Baseline Demographic and Clinical Characteristics

The pooled analysis revealed that the overall mortality among ICU patients with gastrointestinal bleeding was 18.5% (95% CI: 15.2%–22.3%), indicating a substantial mortality burden. There was moderate to high heterogeneity across studies (I² = 72%), likely attributable to variations in patient populations, ICU settings, and treatment protocols. Despite this heterogeneity, the direction of effect remained consistent across studies, with most reporting mortality rates between 15% and 22%. Higher mortality rates were observed in studies including patients with septic shock, multi-organ failure, and advanced comorbidities.

Analysis of predictors demonstrated that multiple clinical, laboratory, and treatment-related factors were significantly associated with increased mortality. Advanced age showed a modest but statistically significant association, with an odds ratio (OR) of 1.04 per year increase. Hemodynamic instability, particularly shock, emerged as the strongest predictor, with a pooled OR of 3.10, indicating more than a threefold increase in mortality risk. Similarly, the requirement for mechanical ventilation (OR 2.80) and renal replacement therapy (OR 2.30) were strongly associated with poor outcomes, reflecting the impact of organ failure.

Table 3: Pooled Predictors of Mortality

Laboratory parameters also played an important role in predicting outcomes. Elevated serum lactate levels were strongly associated with mortality (OR 2.60), highlighting the role of tissue hypoperfusion and metabolic stress. Additionally, higher SOFA scores demonstrated a significant correlation with mortality, emphasizing the importance of multi-organ dysfunction in determining prognosis.

Subgroup analysis further demonstrated variations in mortality based on clinical characteristics. Patients with upper gastrointestinal bleeding had higher mortality (20.2%) compared to those with lower gastrointestinal bleeding (14.8%). The presence of shock and need for mechanical ventilation were associated with markedly increased mortality, reaching up to 28.5% and 25.7%, respectively. Patients with underlying liver disease also showed significantly higher mortality.

Table 4: Subgroup Analysis of Mortality

Sensitivity analysis, performed by excluding low-quality studies, showed minimal change in pooled mortality estimates (17.9% vs 18.5%), confirming the robustness of the findings. Furthermore, assessment of publication bias using funnel plots and Egger’s test suggested minimal bias, supporting the reliability of the results.

Overall, the findings of this meta-analysis indicate that gastrointestinal bleeding in ICU patients is associated with consistently high mortality, and that outcomes are strongly influenced by the severity of illness, presence of organ dysfunction, and biochemical indicators such as lactate.

Figure 2. Forest Plot of Pooled Mortality in ICU Patients with Gastrointestinal Bleeding; Forest plot showing pooled mortality rates among ICU patients with gastrointestinal bleeding using a random-effects model. Individual studies are represented by squares proportional to study weight, with horizontal lines indicating 95% confidence intervals. The diamond represents the pooled estimate of mortality (18.5%, 95% CI: 15.2–22.3%). Moderate-to-high heterogeneity was observed (I² = 72%).

Figure 3. Forest Plot of Predictors of Mortality; Forest plot depicting pooled odds ratios (OR) for significant predictors of mortality in ICU patients with gastrointestinal bleeding. Variables analyzed include shock, mechanical ventilation, renal replacement therapy, elevated lactate, liver disease, and severity scores. Shock demonstrated the strongest association with mortality (OR ~3.10), followed by mechanical ventilation and elevated lactate.

DISCUSSION

This systematic review and meta-analysis evaluated outcomes and predictors of mortality in ICU patients with gastrointestinal bleeding (GIB), synthesizing evidence from 18 studies comprising approximately 32,000 patients. The findings demonstrate that GIB in critically ill patients is associated with substantially high mortality (~18–20%), significantly exceeding that reported in non-ICU populations [1,2,14]. More importantly, mortality appears to be driven not solely by the bleeding event itself, but by the severity of underlying critical illness and the extent of organ dysfunction [3,15,28].

A key finding of this analysis is the consistent and strong association between hemodynamic instability (shock) and mortality, with pooled estimates suggesting more than a threefold increase in risk [4,7]. This observation aligns with the pathophysiological understanding that hypovolemia and impaired tissue perfusion lead to multi-organ dysfunction, thereby compounding the adverse outcomes of GIB [5,19]. Early identification and aggressive management of shock—including timely fluid resuscitation, vasopressor support, and source control—remain central to improving survival [6,11,29].

The requirement for organ support interventions, particularly mechanical ventilation and renal replacement therapy, also emerged as significant predictors of mortality [7,16]. These findings highlight that GIB in ICU settings often occurs in the context of advanced systemic illness, where respiratory and renal failure serve as markers of disease severity rather than isolated complications [8,20,21]. Mechanical ventilation may additionally contribute to stress-related mucosal damage and increased bleeding risk, while renal dysfunction is associated with coagulopathy and impaired hemostasis [9,17,18].

Another important observation is the prognostic value of severity scoring systems, such as the Sequential Organ Failure Assessment (SOFA) and Simplified Acute Physiology Score (SAPS II). These scores demonstrated a strong correlation with mortality across included studies, reinforcing their utility in risk stratification [10,20,21]. Unlike traditional GIB-specific scores (e.g., Glasgow-Blatchford or Rockall), which are primarily designed for non-ICU populations, these ICU-based scoring systems better capture the global burden of organ dysfunction, making them more applicable in critically ill patients [22,25,30].

Among biochemical markers, serum lactate emerged as a robust and consistent predictor of mortality [6,24]. Elevated lactate reflects tissue hypoxia and impaired perfusion, serving as an early indicator of circulatory failure [6,19]. Its strong association with mortality in this meta-analysis supports its routine use as a prognostic biomarker in ICU patients with GIB [9,24]. Similarly, low hemoglobin levels and coagulopathy further contribute to adverse outcomes by exacerbating oxygen delivery deficits and impairing hemostasis [4,12].

Comorbid conditions, particularly chronic liver disease and renal dysfunction, were also associated with increased mortality [5,8,26]. Liver disease predisposes patients to portal hypertension, variceal bleeding, and coagulopathy, all of which complicate management and worsen prognosis [8,15]. The interplay between sepsis, systemic inflammation, and gastrointestinal mucosal integrity further amplifies bleeding risk and mortality in ICU settings [7,9].

Subgroup analysis revealed that upper gastrointestinal bleeding was associated with higher mortality compared to lower gastrointestinal bleeding [2,25]. This may be attributed to the higher prevalence of variceal hemorrhage, peptic ulcer disease, and hemodynamic instability in upper GI bleeding [2,13]. Additionally, patients presenting with shock or requiring mechanical ventilation demonstrated markedly higher mortality rates, emphasizing the importance of early risk stratification and targeted management in these high-risk groups [4,7,16].

The findings of this study are consistent with prior literature but extend existing knowledge by providing a comprehensive synthesis focused specifically on ICU populations [1,3,28]. While earlier studies have largely examined predictors of bleeding occurrence, this analysis emphasizes predictors of mortality, which are more clinically relevant for guiding management decisions and resource allocation in critical care settings [3,27].

Clinical Implications

The results of this meta-analysis have important implications for clinical practice. First, they underscore the need for early identification of high-risk patients using readily available clinical and laboratory parameters [6,23]. Second, they support the integration of ICU-specific severity scores (e.g., SOFA, SAPS II) into routine assessment of patients with GIB [10,20]. Third, they highlight the importance of multidisciplinary management, including intensivists, gastroenterologists, and interventional radiologists, to optimize outcomes [11,29].

Early endoscopic evaluation, appropriate transfusion strategies, correction of coagulopathy, and timely initiation of organ support remain essential components of care [11,12]. Additionally, monitoring of lactate levels and hemodynamic parameters can aid in guiding resuscitation and assessing response to therapy [6,24].

Strengths and Limitations

This study has several strengths, including a large pooled sample size, inclusion of contemporary studies, and comprehensive evaluation of multiple predictors across diverse ICU settings [1,3]. The use of a random-effects model enhances the generalizability of findings [3].

However, certain limitations must be acknowledged. First, significant heterogeneity was observed across studies, likely reflecting variations in patient populations, definitions of GIB, and management protocols [3,28]. Second, the majority of included studies were observational in nature, which may introduce confounding and bias [1]. Third, variability in reporting of predictors and outcomes limited the ability to perform more detailed subgroup analyses [4].

Future Directions

Future research should focus on:

• Development of ICU-specific risk prediction models for GIB mortality [24,30]
• Prospective validation of identified predictors [3]
• Evaluation of early intervention strategies in high-risk patients [6,11]
• Integration of machine learning approaches for improved prognostication [24]

In summary, this meta-analysis demonstrates that gastrointestinal bleeding in ICU patients is associated with high mortality driven primarily by severity of illness and organ dysfunction [1–3,28]. Key predictors such as shock, need for organ support, elevated lactate, and high severity scores provide valuable tools for early risk stratification [4,6,10,20]. Targeted interventions in high-risk patients may help reduce mortality and improve clinical outcomes [11,29].

CONCLUSION

Gastrointestinal bleeding in ICU patients is associated with high mortality (~18–20%), primarily driven by the severity of underlying illness and organ dysfunction. Key predictors—including shock, need for mechanical ventilation, renal replacement therapy, elevated lactate, and high severity scores—enable early risk stratification. Prompt recognition and targeted management of high-risk patients are essential to improve clinical outcomes.

Conflict of Interest

The authors declare no conflict of interest.

Funding

No external funding was received for this study.

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