Timing of Admission to the Surgical Intensive Care Unit is Associated with in-Hospital Mortality

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J Acute Care Surg. 2022;12(1):11-17

Publication date (electronic) : 2022 March 24

doi : https://doi.org/10.17479/jacs.2022.12.1.11

Mi Kyoung Kim^a, Eun-Joo Jung^b, Seulkee Park^b, Im-kyung Kim^a,

^aDivision of Surgical Critical Care, Department of Surgery, Yonsei University College of Medicine, Seoul, Korea

^bDivision of Hospital Medicine, Department of Surgery, Yonsei University College of Medicine, Seoul, Korea

^*Corresponding Author: Im-kyung Kim, Division of Surgical Critical Care, Department of Surgery, Yonsei University College of Medicine, 50–1 Yonsei-ro, Seodaemun-gu, Seoul 03722, Korea, E-mail: ELLE0119@naver.com

Received 2021 April 15; Revised 2021 July 8; Accepted 2021 September 7.

Abstract

Introduction

Adequate treatment within the first few hours after an initial insult is an important factor influencing treatment outcomes in critically ill patients [1,2]. Patients can develop a critical condition at any time, hence, critical care needs to be readily available. Previous studies have reported that higher levels of staffing with intensivists in the intensive care unit (ICU) led to significant reductions in ICU and subsequent in-hospital mortality, and in the length of hospital stay [3–8]. These improved outcomes were observed not only in the medical ICU but also in the surgical ICU (SICU) [9]. However, it might not always be possible to staff the ICU with intensivists beyond their regular working hours to cover nights and weekends because of limited resources and high costs.

Most previous studies have focused on patient outcomes related to intensivist staffing during the after-hours of medical ICUs [10–14]. The clinical outcomes in patients admitted to the SICU during the after-hours remain unclear. This study therefore aimed to evaluate whether SICU admission during the after-hours (any time when the ICU was not staffed with intensivists) was associated with higher in-hospital mortality compared with admission during work-hours.

Materials and Methods

Results

1. Clinicodemographic characteristics

A total of 333 (58.3%) and 238 (41.7%) patients were admitted to the SICU during work-hours, and after-hours, respectively. The patients in the work-hours group were significantly older than those in the after-hours group. The number of patients with an APACHE II score of ≥ 25 was 2 times higher in the after-hours group compared with the work-hours group (23.9% vs. 11.1%, p < 0.001). Moreover, the proportion of patients with unplanned admissions, ventilator support, and vasopressor administration was also higher in the after-hours group (Table 1).

Table 1

Clinicodemographic characteristics of the 571 SICU patients according to the timing of SICU admission.

2. Comparison of clinical outcomes between groups

The rate of ICU readmission within 48 hours was not significantly different between the 2 groups (1.3% vs. 0.3%, p = 0.313). The median length of hospital stay was 20, and 15 days in the after-hours, and work-hours groups, respectively (p < 0.001). The in-hospital mortality rate was approximately 3 times higher in the after-hours group compared with the work-hours group (7.6% vs. 2.7%, p = 0.007; Table 2).

Table 2

Comparison of clinical outcomes between groups.

3. Univariate and Multivariate logistic regression analysis for in-hospital mortality

Multivariate analyses showed that the time of SICU admission (work-hours or after-hours) was an independent risk factor for in-hospital mortality [odds ratio (OR), 2.526; 95% confidence interval (CI), 1.010–6.320; p = 0.048]. Unplanned admission (OR, 21.607; 95% CI, 2.789–167.407; p = 0.003), and ventilator support (OR, 52.269; 95% CI, 6.920–394.808; p < 0.001) were also clinically significant independent predictors of in-hospital mortality (Table 3).

Table 3

Univariate and multivariate logistic regression models for factors associated with in-hospital mortality.

Table 4

Clinicodemographic characteristics and outcomes according to the time of admission in 348 patients who had planned SICU admissions.

4. Subgroup analysis in the planned and unplanned admission cohort

The planned, and unplanned admission subgroups comprised 348, and 223 patients, respectively. The proportion of patients with ventilator support or who required vasopressors was also higher in the after-hours group compared with the work-hours group (27.0% vs. 4.1%, p < 0.001; 38.9% vs. 16.7%, p < 0.001). The median length of hospital stay was significantly longer in the after-hours group compared with the work-hours group (18 days vs. 14 days, p < 0.001). Only 1 patient died (in-hospital mortality: 0.28%) in the planned admission subgroup.

There were 26 patients who died in the unplanned admission subgroup (in-hospital mortality 10.31%). There was no significant difference between the after-hours and work-hours groups in terms of the median length of hospitalization (20 days vs. 18 days, p = 0.977), and in-hospital mortality (15.2% vs. 8.1%, p = 0.100) in the unplanned admission subgroup (Table 5). In multivariate analysis, the time of SICU admission (work-hours or after-hours) was not associated with increased in-hospital mortality in the unplanned admission subgroup (OR: 2.449; 95% CI: 0.970–6.180; p = 0.058; Table 6).

Table 5

Clinicodemographic characteristics and outcomes according to the time of admission in the 223 patients who had unplanned SICU admissions.

Table 6

Subgroup analysis using univariate and multivariate logistic regression models for predictors of in-hospital mortality in the 223 patients who had unplanned SICU admissions.

Discussion

Previous studies have shown that the level of intensivist staffing in the ICU leads to a significant reduction in mortality and length of hospital stay [3–9]. However, the Society of Critical Care Medicine guidelines do not recommend 24/7 intensivist staffing in the ICU in high-intensity ICU models [5] based only on a randomized cohort study conducted in a medical ICU [15]. To date, there is a lack of evidence regarding the safety of admission to the SICU during after-hours.

This study investigated whether SICU admission during after-hours was associated with in-hospital mortality compared with admission during work-hours. It was determined that admission to the SICU during the after-hours period increased in-hospital mortality. Moreover, unplanned admissions, APACHE II score ≥ 25, the need for ventilator support, and the administration of vasopressor drugs were also markedly higher in the after-hours group compared with the work-hours group. These findings are important for the allocation and distribution of ICU resources, including intensivists.

According to 2 systematic reviews, while patients admitted to an ICU over the weekend were at a higher risk of dying, admission to the ICU overnight did not appear to be associated with increased mortality [16,17]. The authors inferred that low levels of staffing and intensity of care provided by many hospitals over the weekend might account for this finding [5,16,17]. In this current study, “after-hours” was defined as the absence of intensivists, and the results showed increased mortality in patients admitted to the SICU. Although there was no change in the level of nursing staff, intensity of care, and intensivists available for real-time consultations, the absence of an intensivist on the SICU may affect resolute decisions which are required during the care of patients with a critical illness.

A recent study reported that ICU admission after elective surgery during the after-hours was associated with significantly higher rates of postoperative complications, increased length of hospital stays, and increased inter-hospital transfers [18]. In this current study, the subgroup analysis of patients admitted for planned surgery showed a significantly higher severity of illness as measured by the APACHE II score, and use of ventilator or vasopressors in the after-hours group compared with the work-hours group. The length of hospitalization in the after-hours group was significantly higher than the work-hours group (work-hours vs. after-hours = 14 days vs. 18 days, p < 0.001). Further analysis was performed on the estimated blood loss and duration of the operation in this subgroup. In the after-hours group, the patients with planned admissions experienced more blood loss (work-hours vs. after-hours = 417.72 ± 647.09 minutes vs. 1,026.98 ± 1,503.99 minutes, p < 0.001) and longer operation times (work-hours vs. after-hours = 298.56 ± 160.58 minutes vs. 500.20 ± 212.18 minutes, p < 0.001, data not shown). This result suggests that cases with unexpected events during the operation are referred to the SICU after-hours, and this has an effect on the status of the patients’ severity of illness.

Even though admission after-hours showed increased in-hospital mortality in the entire cohort, other predictors,

Despite the retrospective design and short study period of this investigation, the findings may reflect the current status of most ICUs in South Korea, considering that 82.3% of all ICUs are either university teaching hospitals or university-affiliated hospitals [19]. One of the main strengths of this study was that surgical patients were specifically targeted. Recently, Kyu et al [20] conducted a retrospective observational study of 10,708 postoperative patients and reported an increased risk of 30-day mortality in the group without intensivist cover. Compared to previous studies which were performed in mixed or medical ICUs [12,14,21–28], this study only focused on postoperative SICU admissions. This study included patients with unplanned admission, including those who underwent emergency operations and those who developed postoperative sepsis, bleeding, or other medical complications, as well as those who had an elective postoperative status. Thus, the patients in this study represented the general population of patients who required postoperative intensive care, and the results were consistent with those of previous studies [18,20,29]. Additionally, subgroup analyses was performed according to the causes of SICU admission to adjust for the negative effects of unplanned admission on mortality.

In conclusion, admission to the SICU during the after-hours was associated with increased in-hospital mortality. These findings may provide a guide to hospitals for improved patient safety and the allocation of ICU resources. Staffing with 24/7 intensivist is considered ideal, but it should be operated flexibly according to each hospital’s human and material resources.

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