Effects of closed- versus open-system intensive care units on mortality rates in patients with cancer requiring emergent surgical intervention for acute abdominal complications: a single-center retrospective study in Korea
Article information
Abstract
Background
In this study, we aimed to compare the in-hospital mortality of patients with cancer who experienced acute abdominal complications that required emergent surgery in open (treatment decisions made by the primary attending physician of the patient's admission department) versus closed (treatment decisions made by intensive care unit [ICU] intensivists) ICUs.
Methods
This retrospective, single-center study enrolled patients with cancer admitted to the ICU before or after emergency surgery between November 2020 and September 2023. Univariate and logistic regression analyses were conducted to explore the associations between patient characteristics in the open and closed ICUs and in-hospital mortality.
Results
Among the 100 patients (open ICU, 49; closed ICU, 51), 23 died during hospitalization. The closed ICU group had higher Acute Physiology and Chronic Health Evaluation (APACHE) II scores, vasopressor use, mechanical ventilation, and preoperative lactate levels and a shorter duration from diagnosis to ICU admission, surgery, and antibiotic administration than the open ICU group. Univariate analysis linked in-hospital mortality and APACHE II score, postoperative lactate levels, continuous renal replacement therapy (CRRT), and mechanical ventilation. Multivariate analysis revealed that in-hospital mortality rate increased with CRRT use and was lower in the closed ICU.
Conclusions
Compared to an open ICU, a closed ICU was an independent factor in reducing in-hospital mortality through prompt and appropriate treatment.
INTRODUCTION
The incidence of many cancers continues to increase worldwide albeit with variations according to cancer type. Substantial progress over the past few decades in diagnosis, treatment, and rehabilitation has resulted in higher survival rates and an increase in age of cancer survivors [1]. However, patients with cancer are highly susceptible to sepsis due to the immunosuppressive state induced by treatment, leading to a poor prognosis. The proportion of cancer patients requiring intensive care unit (ICU) treatment is increasing, ranging from 9.8% to 16.5% of total admissions [2-4]. Most cancer patients seen in the ICU (62.4%–64.2%) are admitted for postoperative care, with emergency surgery mortality rates as high as 37%, exceeding the overall cancer patient mortality rate of 30% [4]. Additionally, cancer patients experience higher rates of complications such as pneumonia and acute respiratory failure than non-cancer patients [5].
Unlike other medical departments, ICUs are characterized by a close association between structure, operational system, and patient treatment outcomes. The medical team responsible for patient care is central to this system [6]. Despite extensive research on ICU specialists’ staffing patterns and their impacts on in-hospital outcomes, there is ongoing debate regarding the optimal ICU staffing strategy [7-10]. In particular, ICUs can be categorized as open or closed based on staffing patterns. In open ICUs, primary physicians lead patient management, while in closed ICUs, ICU specialists are fully responsible for patient management, offering advantages such as better coordination and efficient resource utilization [11-14].
Few studies have investigated the impact of ICU type on the mortality of cancer patients requiring emergency surgery. We hypothesized that closed ICUs may offer a survival benefit over open ICUs in these critically ill patients. Thus, we aimed to compare and analyze the outcomes of cancer patients in open versus closed ICUs after emergency surgery for acute abdominal complications and to identify factors associated with in-hospital mortality to suggest potential interventions.
MATERIALS AND METHODS
Ethical Considerations
This study was performed in accordance with the principles of the Declaration of Helsinki and was approved by the Institutional Review Board of National Cancer Center (No. NCC 2023–0319). The data access period for the manuscript was from November 15, 2023 (date of Institutional Review Board approval) to December 31, 2023. Identifiable information of individual participants was accessed during the data collection period but we refrained from accessing data after the data collection period ended. The requirement for informed consent was waived owing to the retrospective nature of the study.
Study Design
This single-center, retrospective study was conducted between November 2020 and September 2023, and included 100 patients with cancer admitted to the ICU before or after emergency surgery for acute abdominal complications. Acute abdominal complications were defined as abrupt-onset abdominal pain requiring urgent intervention owing to intra-abdominal pathology [15]. Patients included in the study were those admitted to the ICU before or after surgery, extracted from among those diagnosed with acute abdominal complications confirmed by computed tomography imaging. Retrospective evaluation of the interval from computed tomography diagnosis to ICU admission, surgery, and antibiotic administration was conducted to assess the timing of these interventions. Patients with a “do-not-resuscitate” status or who discontinued life-sustaining treatment, those who did not undergo surgical treatment before or after ICU admission for acute complications, and those who underwent elective surgery after diagnosis were excluded.
In the present study, patients were categorized into closed and open ICU groups. In our institution, both open and closed ICU systems are operational. Patients were categorized into the closed ICU group if their ICU admission and management were determined by ICU specialists. Conversely, the open ICU group included patients managed primarily by the attending physicians of their respective departments with ICU specialists consulted as needed [13]. In the closed ICU group, all patients were those who were recommended to undergo surgery by an intensivist and who subsequently received postoperative care. For both closed and open ICU groups, patients admitted preoperatively typically had unstable hemodynamic indicators and required invasive interventions such as mechanical ventilation and vasopressors before surgery. Conversely, patients admitted postoperatively generally had a relatively stable hemodynamic status prior to surgery but required intensive management and monitoring in the ICU after surgery. Figure 1 displays the flow diagram of participant selection.
Flowchart of the participant selection process. ICU: intensive care unit.
Patient Characteristics
Patient characteristics included sex, age, comorbidities (diabetes mellitus, hypertension, cardiovascular disease, chronic obstructive pulmonary disease, chronic kidney disease, and liver cirrhosis), cancer type (gastrointestinal, genitourinary, and other cancers), cancer stage (determined according to the American Joint Committee on Cancer 8th edition) [16], operative site (lower gastrointestinal tract, upper gastrointestinal tract, and others), reasons for surgery (perforation, ischemia, bleeding, and others), disease severity (American Society of Anesthesiologists [ASA] score, Acute Physiology and Chronic Health Evaluation II [APACHE II] score, Sequential Organ Failure Assessment [SOFA] score; APACHE II and SOFA scores were calculated within 24 hours of ICU admission), use and duration of vasopressors, application and duration of mechanical ventilation, continuous renal replacement therapy [CRRT], interventions excluding surgical treatment (percutaneous drainage catheter insertion, percutaneous dilatational tracheostomy, embolization, bronchoscopy, and endoscopy), preoperative and postoperative lactate levels, presence of neutropenia, postoperative lactate clearance (calculated as follows: [lactate (preoperative) – lactate (postoperative)] × 100/lactate (preoperative)] [17], preoperative laboratory data (procalcitonin, C-reactive protein, albumin, and cholesterol levels), blood culture results, time from diagnosis to ICU admission, time from diagnosis to surgery, time from diagnosis to antibiotic administration, ICU stay duration, postoperative length of hospital stay, and in-hospital mortality. Logistic regression analysis was performed to compare all variables and analyze factors in the open and closed ICU groups that influenced in-hospital mortality.
Statistical Analysis
Continuous variables that satisfied normality assumptions are presented as descriptive statistics, such as mean±standard deviation, and t-tests were used to compare means between groups. Data that did not meet normality assumptions are described as the median (minimum–maximum), and the non-parametric Wilcoxon rank-sum test was used to compare the distributions of these variables between the two groups. Categorical variables were compared using the chi-square test or Fisher’s exact test. Logistic regression analysis was performed to investigate factors predicting in-hospital mortality. Initially, a univariate analysis was applied to assess the significance of each variable as an independent risk factor. Subsequently, a backward-stepwise elimination method was used to select variables with P-values <0.2 to avoid overfitting bias and to optimize the Akaike information criterion. The final model included only variables with sufficiently adjusted significance for predicting in-hospital mortality. Odds ratios (ORs) and 95% CIs were calculated for all variables. Kaplan-Meier analysis was conducted to compare in-hospital mortality between open and closed ICUs. Statistical analyses were performed using SAS version 9.4 for Windows (SAS Institute).
RESULTS
Characteristics of Patients with Acute Abdominal Complications Who Underwent Surgical Intervention
Among the 100 patients, 51% received treatment in a closed ICU, while 49% were treated in an open ICU. The mean age of the patients was 65 years, and 23% of patients died during hospitalization. Among them, 47.8% chose to discontinue life-sustaining measures after surgery, 43.5% succumbed to multi-organ failure due to septic shock, and 8.7% succumbed to multi-organ failure due to septic shock during surgery. The most common type of cancer was gastrointestinal, accounting for 47% of cases. Stage IV cancer was the most common cancer stage, accounting for 50% of cases. Perforation was the most common reason for surgery (70%), followed by ischemia (18%), other reasons (7%), and bleeding (5%). Mean APACHE II score was 29.7±5.7, and median SOFA score was 3 (2–6). Median (interquartile range [IQR]) ICU ICU stay duration was 2.3 days (0.7–4.5), and postoperative length of hospital stay was 23.7 days (14.5–38.5) (Table 1).
Demographic profiles and patient outcomes in patients with cancer requiring emergency surgery for acute abdominal complications: results of the comparative analysis between open and closed ICUs
Neutropenia was present before surgery in 11% of patients, and 36% had confirmed bacteremia. Times from diagnosis to ICU admission, surgery, and antibiotic administration were 9.0 hours (2.6–14.7), 7.7 hours (4.8–14.0), and 3.6 hours (2.0–6.4), respectively. In total, 59% received vasopressors, and the duration of use was 1.5 days (0.8–2.5). Overall, 60% received mechanical ventilation therapy, with a duration of 1.2 days (0.7–2.7). Eighteen percent of patients underwent CRRT for acute renal failure, acidosis, electrolyte imbalance, and volume overload for a median duration of 3.0 days (0.5-9.1). In total, 25% of patients underwent interventions other than surgical treatment (Table 2).
Laboratory metrics and clinical parameters: comparative analysis between open and closed ICUs for patients with cancer requiring emergent surgery for acute abdominal complications
Comparison of Open Versus Closed ICUs
Patients in the open ICU predominantly had gastrointestinal-type cancer (53.1%), while those in the closed ICU mostly had genitourinary cancer (52.9%). Stage IV cancer was most common in the open ICU (63.3%), whereas stage III was more prevalent in the closed ICU (39.2%). There were no significant differences between the two groups regarding the surgical site or reasons for surgery. Patients treated in the closed ICU had a higher proportion of high ASA scores and higher APACHE II scores. Preoperative ICU admissions were more frequent in the closed ICU than the open ICU (P=0.001). Patients in the closed ICU had longer ICU stays (3.2 days vs. 0.9 days) and postoperative hospital stays (25.6 days vs. 18.9 days). Postoperative in-hospital mortality was slightly lower in the closed ICU than the open ICU (17.7% vs. 28.6%), but this difference was not statistically significant (Table 1).
Patients in the open ICU had lower preoperative lactate and procalcitonin levels than those in the closed ICU. Postoperative lactate levels and lactate clearance were not significantly different between the open and closed ICUs. Neutropenia before surgery was less common in the open ICU, while postoperative neutropenia was more frequent in the closed ICU. Positive blood cultures before surgery were less frequent in the open ICU. Patients in the closed ICU required more ventilators and vasopressors, and had a higher rate of non-surgical interventions. However, the duration of ventilator assistance and vasopressor application did not differ significantly between the two groups. Patients in the closed ICU had shorter time intervals from diagnosis to ICU admission and diagnosis to operation than those in the open ICU (Table 2).
Univariable and Multivariable Analyses for In-Hospital Mortality
Univariable analysis was conducted to investigate factors influencing in-hospital mortality in patients admitted to the ICU before or after surgical treatment for acute abdomen. The analysis revealed that higher APACHE II score, elevated postoperative lactate level, the need for CRRT, and mechanical ventilation were factors associated with in-hospital mortality. Multivariable analysis using backward stepwise regression identified two factors that remained significantly associated with in-hospital mortality: the requirement for CRRT and treatment in a closed ICU. Although APACHE II score, postoperative lactate level, and time from diagnosis to operation showed some associations with in-hospital mortality in the multivariable analysis, the statistical significance of these associations was relatively low (Table 3, Figure 2).
Results of univariable and multivariable logistic regression analyses of factors associated with in-hospital mortality
Forest plot of the odds ratios (ORs) for in-hospital mortality of patients with cancer requiring emergent surgery for acute abdominal complications. Treatment in the closed intensive care unit (ICU) was associated with decreased in-hospital mortality compared with the open-type ICU (P=0.025), and continuous renal replacement therapy (CRRT) was associated with increased mortality (P=0.032). Acute Physiology and Chronic Health Evaluation (APACHE) II score, postoperative lactate level, and time from diagnosis to operation were not significantly associated with in-hospital mortality.
Survival Analysis: Open ICU Versus Closed ICU during Postoperative Hospitalization
The closed ICU group demonstrated a higher survival rate than the open ICU group (82.4% vs. 71.4%, respectively) (Table 1). Additionally, the closed ICU group had a higher overall survival rate during the postoperative hospitalization period than the open ICU group (P=0.033) (Figure 3).
Kaplan-Meier survival analysis based on the type of intensive care unit (ICU) for patients with cancer requiring emergent surgical intervention for acute abdominal complications. Cumulative survival rate was significantly higher in the closed ICU group than in the open ICU group (P=0.033). The log-rank test was applied to compare survival curves.
DISCUSSION
In the present study, we compared in-hospital mortality rates in patients with cancer with acute abdominal complications that required emergent abdominal surgery in open versus closed ICUs. Our results confirmed that a closed ICU is a standalone factor in reducing in-hospital mortality in patients admitted to the ICU after emergency surgery, compared with open ICUs. Recent advances in critical care, such as the development of ventilators and medical devices and application of treatment bundles led by trained specialists have transformed the treatment approach for critically ill patients [18]. In Korea, a dedicated specialist system is in operation, with specialists from various fields, including internal medicine (30%), anesthesiology (18%), neurosurgery (12%), emergency medicine (11%), thoracic surgery (11%), and general surgery (7%) all serving as intensive care specialists [19]. However, as of 2020, 44% of ICUs globally operate using an open model, and in Korea, only 41.1% of intensive care patients receive treatment from intensive care specialists [11,19].
Practical roles of intensivists are assessment of patients in the ward, providing expert advice, making timely decisions, managing access to the ICU, and holding the final decision-making authority. Sometimes, they are also tasked with determining whether to limit treatment [20]. These roles have been shown to contribute to reducing nonadherence to evidence-based care processes and decreasing the rate of complications, potentially leading to a decrease in the length of hospital stay [10]. In our study, patients in the closed ICU had higher values of severity indicators (APACHE II scores) than those in the open ICU. Despite this, time intervals from diagnosis to ICU admission, surgery, and antibiotic administration were lower in the closed ICU than open ICU. Intensivists also implement systematic treatment protocols and present expertise in invasive treatments, such as mechanical ventilation and CRRT. Our findings highlight the potential benefits of closed ICUs in improving clinical outcomes in patients undergoing emergency surgery for acute abdominal illnesses.
Previous studies have shown mixed results regarding the impact of neutropenia on postoperative outcomes [4,21]. In our study, although the proportion of patients with pre- and postoperative neutropenia was higher in the closed ICU group than the open ICU group, there was no significant difference in in-hospital mortality between the two groups. Furthermore, multivariate analysis revealed no association between neutropenia and in-hospital mortality, suggesting that surgery can be beneficial even in patients with neutropenia.
Lactate levels are widely used as an indicator of tissue hypoxia and for risk stratification in various clinical conditions, including predicting mortality [22-26]. However, in our study, although preoperative lactate levels were higher in the closed ICU group than the open ICU group, no correlation with in-hospital mortality was observed. The relatively low lactate levels in our study may explain the lack of association with mortality. This may also be due to the inclusion of patients who did not experience shock. Additionally, combining lactate levels with other variables, such as the quick SOFA score, may improve predictive accuracy, as suggested by another study [26]. Based on our study results, lactate levels alone may be insufficient to predict mortality.
Recently, CRRT has emerged as an independent factor associated with increased in-hospital mortality. CCRT is a crucial renal replacement therapy in ICUs used to maintain volume control, acid-base and electrolyte balance, and hemodynamic stability. Several previous studies have investigated the optimal timing, modality, and dosing strategies for CRRT, as approximately 11%–20% of patients with sepsis hospitalized in the ICU may require RRT owing to renal insufficiency [27-29]. Untreated acute kidney injury can increase in-hospital mortality rates, especially when CRRT is administered to patients with cancer, with reported mortality rates of 55.9%–68% [30,31]. In our study, 56% of patients treated with CRRT died, which is consistent with previous findings.
Our study showed a trend towards better outcomes with a shorter duration from diagnosis to emergency abdominal surgery, although without statistical significance. This observation is supported by previous studies that have reported that reducing the time to surgery can significantly decrease mortality and complications. For example, timely surgical intervention in gastrointestinal perforations and bowel perforations is associated with improved survival rates and fewer severe complications [32,33]. These findings emphasize the importance of minimizing delays to enhance patient outcomes after emergency abdominal surgery.
This study had some limitations that should be noted when interpreting our findings, including a small sample size, single-center design, and retrospective nature. Furthermore, there were differences in cancer type and sex between the two ICU models, which we attribute to challenges in managing patients with gynecological cancers in open ICUs. These patients are mostly referred for closed ICU management because of the difficulty of open ICU treatment of gynecological cancers, leading to disparities. Although treatment of patients in the closed ICU reduced the in-hospital mortality rate, closed ICU treatment was associated with prolonged lengths of ICU and postoperative hospital stays compared with open ICU treatment, likely due to inherent differences in baseline disease severity. Additionally, the improvement in survival rate due to treatment of severe complications may have led to increased ICU and postoperative hospitalization durations. While not statistically significant, the duration of mechanical ventilation and vasopressor use was longer in the closed ICU group (median of 3.23 days in the closed ICU group compared to 0.92 days in the open ICU group; P=0.821). Furthermore, although the overall number of patients receiving tracheostomy was low, more patients in the closed ICU group underwent this procedure than those in the open ICU group. It is important to note that disease severity scores (APACHE II and SOFA) were assessed within the first 24 hours of ICU admission. Given the retrospective design of this study, which utilized data from medical records, we were unable to capture severity scores at the time of diagnosis. This limitation may have constrained a complete evaluation of patients' initial clinical status. Finally, our study only analyzed short-term outcomes from emergency surgery for acute abdominal illness to discharge. Therefore, future multicenter, long-term studies should be performed to assess the impact of closed ICU treatment on the survival of patients with acute abdominal conditions.
Despite these limitations, we demonstrated that a closed ICU system allows more appropriate treatment after the diagnosis of patients with cancer and acute abdominal conditions that require emergency surgery, thereby reducing in-hospital mortality post-surgery. Based on these findings, there is a clear need for expanded adoption of closed ICU systems. Furthermore, the establishment of a systematic training program for ICU specialists, a fundamental element of closed ICUs, is essential to improve the outcomes of critically ill patients.
Among patients with cancer who underwent acute abdominal surgery, treatment in a closed ICU and CRRT were associated with reduced in-hospital mortality. Thus, treatment in a closed ICU is an independent factor in reducing in-hospital mortality in critically ill patients by providing timely and appropriate treatment compared with open ICUs. Nevertheless, further research, spanning multiple institutions and a longer observation period, is necessary for further comprehensive analyses of the impact of closed ICU treatment on the prognosis of patients with acute abdominal illnesses.
KEY MESSAGES
▪ Patients in the closed intensive care unit (ICU) group had higher Acute Physiology and Chronic Health Evaluation (APACHE) II scores, increased use of vasopressors, mechanical ventilation, and preoperative lactate levels but experienced shorter times from diagnosis to ICU admission, surgery, and antibiotic administration than the open ICU group.
▪ Multivariate analysis showed that closed ICU management independently reduced in-hospital mortality, highlighting the benefits of prompt and appropriate treatment by ICU intensivists.
Notes
CONFLICT OF INTEREST
No potential conflict of interest relevant to this article was reported.
FUNDING
This study was supported by a research grant from the National Cancer Center (No. NCC 2310350-1).
ACKNOWLEDGMENTS
None.
AUTHOR CONTRIBUTIONS
Conceptualization: WHH. Data curation: KHY, JHL. Formal analysis: JHL. Methodology: KHY, JHK. Funding acquisition: WHH. Writing – original draft: JHL. Writing – review & editing: JHK, KHY, JHL. All authors read and agreed to the published version of the manuscript.