Being admitted to the ICU over the weekend increases risk of dying

by Nancy Walsh

Patients admitted to an intensive care unit (ICU) over the weekend face a greater likelihood of dying compared with those admitted on a weekday, a meta-analysis suggested.

The meta-analysis, encompassing more than 180,000 weekend and weekday ICU admissions, found that even after adjusting for disease severity, the odds ratio for death among those admitted to an ICU over a weekend was 1.08 (95% CI 1.04 to 1.13, P<0.001), according to Rodrigo Cavallazzi, MD, of Thomas Jefferson University in Philadelphia, and colleagues.

“A change in the organizational/staffing structure of an ICU and hospital over the weekend likely explains the increased mortality noted,” the researchers wrote in the July issue of Chest.

Previous studies assessing the effects of off-hour admissions have had conflicting results. To clarify this issue — which has important implications not only for critically ill patients but also for healthcare administrators, policymakers, and insurance providers — Cavallazzi and colleagues undertook a systematic review and meta-analysis of studies evaluating the association of time of ICU admission and mortality.

The comparison of weekend versus weekday admissions included six studies, in which 11.1% of the 133,150 weekday admissions died, as did 15.6% of the 47,450 weekend admissions.

Significant heterogeneity was not seen in that group of studies (P=0.585).

One study represented 64% of the pooled odds ratio for weekend admissions, and when the authors excluded this study, the risk of death remained elevated (OR 1.07, 95% CI 1 to 1.14, P=0.05).

But they noted that this dominant study included only midweek admissions (Tuesday through Thursday) as controls, and it was unclear whether inclusion of all five weekdays would have altered the result.

In addition, although the analysis suggested an 8% higher risk of death for patients admitted to the ICU on the weekend, the authors cautioned that because of sampling variability, the risk could be as low as 4% or as high as 13%.

When they compared the mortality risk in eight studies of daytime versus nighttime admissions, however, they found no difference.

In those studies there were 73,676 daytime admissions, 21.4% of whom died. The corresponding numbers for nighttime admissions were 61,544 and 20.8% (OR 1.0, 95% CI 0.87 to 1.17, P=0.956).

There was significant heterogeneity among these studies, however (P<0.001).

The authors noted that there also have been conflicting results in studies looking at the impact of the presence of intensivists on outcomes of critically ill patients, so they also performed subgroup analyses looking at this.

In the studies comparing daytime and nighttime admissions, they found a significant difference:

* No intensivist, OR 1.05 (95% CI 0.79 to 1.41, P=0.73)
* Intensivist on site, OR 0.93 (95% CI 0.87 to 0.99, P=0.02)

But the effect of intensivist presence on mortality in the studies comparing weekday and weekend admissions was less clear:

* No intensivist, OR 1.07 (95% CI 0.99 to 1.15, P=0.081)
* Intensivist on site, OR 1.03 (95% CI 0.61 to 1.73, P=0.916)

In discussing their findings, Cavallazzi and colleagues suggested that factors that were likely to contribute to the increased mortality risk for weekend admissions included a decreased physician-to-patient ratio, clinician fatigue, and difficulties in obtaining complex diagnostic tests and treatments.

But they noted that it was unclear why the significant increase in mortality risk was only seen for weekend admissions, and not for those occurring at night.

They also pointed out that the significant heterogeneity between some studies probably reflected diverse ICU organizational structures, and said that further studies are needed to more clearly determine the possible effects of structural changes, including the presence of intensivists during off-hours.

Other limitations of the meta-analysis included differing definitions of nighttime and weekend hours, as well as a lack of clarity in descriptions of organizational structures.

In addition, not all studies used similar methods of adjusting for disease severity.

Nonetheless, the analysis does suggest that a lower level of staffing and less intensity of care contributes to an increased risk of ICU mortality on weekends, the authors concluded.

“It is reasonable to presume that efforts to make the organization structure of ICUs (and hospitals) homogeneous during weekdays and weekends will likely have a favorable impact on patient outcomes,” they said.

Nancy Walsh is a MedPage Today staff writer.

Originally published in MedPage Today. Visit for more critical care news.

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  • Happy Hospitalist

    Perhaps people admitted on the weekend are people who waited too long to come in and were therefore sicker on admission, leading to higher inhospital mortality.

    It’s quite possible that staffing at the nursing homes is lower on weekends than on weekdays making patients sicker on arrival to the hospital because nobody is paying attention to them.

    It’s quite possible people drink and smoke more heavily, don’t take their necessary medications and live higher risk lifestyles on weekends than on weekdays leading to sicker presentation of disease on weekends.

    I think there are a lot of reasons why people die more often on weekends.

    I know at my hospital I have 24 hour access to nurses, hospitalists, ER doctors, pulmonologists, cardiologists, dialysis, surgeons, echos, dopplers, medications, drips, fluids.

    We have it all. I have no idea what the weekend vs weekday mortality rates at my hospital, but I could be pretty confident it’s not from a lack of access to vital care needs.

    • ZC

      The idea that people wait to come in on a weekend strikes me as one of the most likely reasons; on a given weekend, anywhere from twenty to thirty percent of the ED patients I see make some comment about how their issue started mid-week but that they couldn’t make it in.

  • Doc D

    There are too many caveats and limitations in this study, heterogeneity in the review set is to me the most significant .

    There’s a definable result, but little to suggest whether it’s an artifact, or where to go to find a cause. I don’t deny that staffing, fatigue, and testing could be at work, but they aren’t the things that I’ve observed in the facilities where I worked.

  • ninguem

    I say selection bias.

  • J.T. Wenting

    Selection bias maybe, but hospitals tend to be understaffed on weekends, so there’s less care per patient over the weekend (heck, many hospitals try to empty their wards over the weekend, sometimes sending patients home with a notice to report back on monday morning if they’re not tied to their beds).

    So there’s more than one thing going on here.
    - patients coming in on the weekend may be in more serious conditions than those coming in during the week on average
    - hospitals tend to be staffed with fewer and lower qualified staff (“let’s let the interns run the weekend shift”).
    - ICU patients admitted over the weekend tend to be a higher percentage ER patients compared to weekdays when there’s more people put in ICU for short term observation after surgery.

    All will contribute to a higher incidence of death for patients admitted to ICU over the weekend.

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