Chest
Volume 138, Issue 1, July 2010, Pages 68-75
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ORIGINAL RESEARCH
CRITICAL CARE MEDICINE
Association Between Time of Admission to the ICU and Mortality: A Systematic Review and Metaanalysis

https://doi.org/10.1378/chest.09-3018Get rights and content

Background

The organizational and staffing structure of an ICU influences the outcome of critically ill and injured patients. A change in the ICU staffing structure frequently occurs at nighttime and on weekends (off-hours). We postulated that patients who are admitted to an ICU during off hours may be at an increased risk of death.

Methods

We performed a systematic review of the literature to assess whether admission to an ICU during off-hours is associated with an increased mortality. We selected studies that evaluated the association between time of admission to the ICU and mortality, with adjustment for severity of disease. We excluded studies that included pediatric and non-ICU patients. Study characteristics extracted included date of publication, study design, country where study was done, study population, time factor (weekend or night shift), severity adjustment tool, and outcome.

Results

Ten cohort studies met our inclusion criteria; eight of these studies evaluated nighttime admissions, whereas six studies evaluated weekend admissions. The pooled analysis demonstrated that nighttime admission was not associated with an increased mortality (odds ratio [OR], 1.0 [95% CI, 0.87-1.17]; P = .956); however, patients admitted over the weekend had a significant increase in the adjusted risk of death (OR, 1.08 [95% CI, 1.04-1.13]; P < .001). Significant heterogeneity was found in the studies that evaluated nighttime admissions.

Conclusions

Whereas patients admitted to an ICU over the weekend appear to be at an increased risk of death, nighttime admissions were not associated with an increased mortality. The lower level of staffing and intensity of care provided by many hospitals over the weekend may account for this finding. The heterogeneity noted between studies evaluating nighttime admissions likely reflects the diverse organizational structure of the hospitals and ICUs where these studies were carried out.

Section snippets

Search Strategy

Two investigators independently searched the Medline and Embase databases through September 2009 using a combination of terms that included “critical care,” “time,” and “admission,” with no restriction to date or language. We also reviewed the bibliographies of all selected articles for other potential relevant articles.

Study Selection

Although the definition of “off-hours” differed among the studies, we use the term “off-hours” to refer to either nighttime or weekend admissions. Thus, studies were eligible to

Results

The Medline and Embase searches retrieved 796 and 173 citations, respectively. After screening the titles and abstracts from these citations and the bibliographic references from relevant articles, we selected 21 studies for full review.5, 6, 7, 8, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26 Although our initial search was not restricted to any specific language, only English-language articles were included in the final analysis.22 Although Arabi et al20 evaluated weekend or

Discussion

The main finding of this metaanalysis is that patients admitted to an ICU over the weekend have an 8% higher risk of death, after adjusting for severity of illness, as compared with patients admitted during weekdays. Accounting for sampling variability, this increased risk could be as low as 4% or as high as 13%. This finding should, however, be viewed with caution because the metaanalysis was dominated by one study.5 Furthermore, the control group in that study included admissions only during

Acknowledgments

Author contributions: Dr Cavallazzi: contributed to the literature search, data extraction, statistics, and writing of the manuscript.

Dr Marik: contributed to the study concept and design, and writing and final editing of the manuscript.

Dr Hirani: contributed to the literature search, data extraction, and review of the manuscript.

Dr Pachinburavan: contributed to the data review and review of the manuscript.

Dr Vasu: contributed to the data review and review of the manuscript.

Dr Leiby:

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