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BACKGROUND

Increasing numbers of intensive care units (ICUs) are adopting the practice of nighttime intensivist staffing despite the lack of experimental evidence of its effectiveness.

Full Text of Background…

METHODS

We conducted a 1-year randomized trial in an academic medical ICU of the effects of nighttime staffing with in-hospital intensivists (intervention) as compared with nighttime coverage by daytime intensivists who were available for consultation by telephone (control). We randomly assigned blocks of 7 consecutive nights to the intervention or the control strategy. The primary outcome was patients’ length of stay in the ICU. Secondary outcomes were patients’ length of stay in the hospital, ICU and in-hospital mortality, discharge disposition, and rates of readmission to the ICU. For length-of-stay outcomes, we performed time-to-event analyses, with data censored at the time of a patient’s death or transfer to another ICU.

Full Text of Methods…

RESULTS

A total of 1598 patients were included in the analyses. The median Acute Physiology and Chronic Health Evaluation (APACHE) III score (in which scores range from 0 to 299, with higher scores indicating more severe illness) was 67 (interquartile range, 47 to 91), the median length of stay in the ICU was 52.7 hours (interquartile range, 29.0 to 113.4), and mortality in the ICU was 18%. Patients who were admitted on intervention days were exposed to nighttime intensivists on more nights than were patients admitted on control days (median, 100% of nights [interquartile range, 67 to 100] vs. median, 0% [interquartile range, 0 to 33]; P<0.001). Nonetheless, intensivist staffing on the night of admission did not have a significant effect on the length of stay in the ICU (rate ratio for the time to ICU discharge, 0.98; 95% confidence interval [CI], 0.88 to 1.09; P=0.72), ICU mortality (relative risk, 1.07; 95% CI, 0.90 to 1.28), or any other end point. Analyses restricted to patients who were admitted at night showed similar results, as did sensitivity analyses that used different definitions of exposure and outcome. 

CONCLUSIONS

In an academic medical ICU in the United States, nighttime in-hospital intensivist staffing did not improve patient outcomes. (Funded by University of Pennsylvania Health System and others; ClinicalTrials.gov number, NCT01434823.)

RESULTS

The study period included 352 nights, 175 of which (50%) were randomly assigned to the intervention; nighttime intensivists staffed 166 (95%) of the intervention nights. A total of 1598 patients were included in the analyses (Figure 1), of whom 970 (61%) were admitted at night (Table 1TABLE 1Characteristics of the Study Population., and Table S1 in the Supplementary Appendix). The median APACHE III score (with scores ranging from 0 to 299 and higher scores indicating more severe illness) was 67 (interquartile range, 47 to 91), and the median length of stay in the ICU was 52.7 hours (interquartile range, 29.0 to 113.4). A total of 381 patients (24%) died in the hospital, including 293 (18%) who died in the ICU.

Nighttime intensivists were generally younger than the daytime intensivists (Table S2 in the Supplementary Appendix), although most (82%) also worked as daytime intensivists during the study period. Nighttime intensivists completed post-shift questionnaires on 116 intervention nights (66%) and reported evaluating a median of 4 (interquartile range, 3 to 5) new patients and 2 (interquartile range, 1 to 3) previously admitted patients per night (Table S3 in the Supplementary Appendix). During the control nights, the at-home intensivists received a median of 2 (interquartile range, 1 to 3) calls each night, and the critical care fellows received a median of 2 (interquartile range, 0 to 3) calls each night (Table S4 in the Supplementary Appendix).

Patients who were admitted on intervention days had greater cumulative exposure to nighttime intensivists than did patients who were admitted on control days (median, 100% of nights [interquartile range, 67 to 100] vs. median, 0% [interquartile range, 0 to 33]; P<0.001). Staffing with nighttime intensivists did not have a significant effect on the length of stay in the ICU (rate ratio for ICU discharge, 0.98; 95% confidence interval [CI], 0.88 to 1.09; P=0.72) (Figure 2AFIGURE 2Kaplan–Meier Curves for Time to Discharge from the ICU.). In this study, the rate ratio refers to the instantaneous rate of discharge from the ICU in the intervention group divided by the instantaneous rate of discharge from the ICU in the control group, such that a rate ratio greater than 1 would indicate that the intervention shortened the time to ICU discharge. The findings were similar in analyses that were restricted to patients admitted at night (hazard ratio, 0.98; 95% CI, 0.84 to 1.13; P=0.74) (Figure 2B), and in several sensitivity analyses (Table 2TABLE 2Primary, Restricted, and Sensitivity Analyses of the Effect of the Intervention.). The results were also similar in the rank-based analysis of length of stay in the ICU, in which deaths were coded as the longest possible length of stay (P=0.51).

Nighttime intensivist staffing also had no significant effect on the length of stay in the hospital (median, 174 hours [interquartile range, 91 to 361] in the intervention group vs. 166 hours [interquartile range, 84 to 328] in the control group; rate ratio, 0.91; 95% CI, 0.82 to 1.02; P=0.12) or on ICU mortality, hospital mortality, readmission to the ICU among ICU survivors, or discharge to home (Table 3TABLE 3Secondary Outcomes.). Analyses that were restricted to patients admitted at night also showed no significant effects of nighttime intensivist staffing.

The patients’ APACHE III score did not modify the effect of the intervention on the length of stay in the ICU (P=0.28 for interaction) (Table S5 in theSupplementary Appendix). The effects of the intervention on the length of stay in the ICU were also similar during periods in which residents were more experienced and those in which residents were less experienced (Table S6 in the Supplementary Appendix). There was significant heterogeneity in the effect of the intervention on readmission to the ICU during the two periods (P=0.03 for interaction). However, the intervention was not associated with significantly fewer readmissions during the inexperienced-resident period (relative risk for readmission, 0.58; 95% CI, 0.10 to 3.39), and the heterogeneity was due, in part, to a nonsignificantly higher readmission rate with the intervention during the experienced-resident period (relative risk for readmission, 1.94; 95% CI, 0.87 to 4.30).

The Web-based surveys were completed by 41 of 91 eligible residents (45%). A majority of residents reported that the presence of nighttime intensivists improved the quality of care as perceived by the resident, provided support to residents, permitted appropriate resident autonomy, and improved the educational experience (Table S7 in the Supplementary Appendix).

DISCUSSION

In this single-center randomized trial of in-hospital nighttime intensivist staffing in an academic medical center in the United States, we found no evidence that this staffing model, as compared with nighttime telephone availability of the daytime intensivist, had a significant effect on length of stay in the ICU or hospital, ICU or in-hospital mortality, readmission to the ICU, or the probability of discharge to home. We also observed no significant benefits of the intervention in subgroups of patients for whom we had hypothesized the greatest effects: patients admitted at night, those with the most severe illness at the time of ICU admission, and those admitted during the period when the residents were least experienced. These findings are consistent with a multicenter observational study that suggested that in hospitals with high-intensity daytime intensivist staffing, the presence of nighttime intensivists did not reduce mortality.14 The current trial extends this work by removing the potential for ICU-level and patient-level confounding and by documenting the lack of significant effects on a broad range of outcomes.

There are several possible explanations for the lack of significant benefit of nighttime intensivists in this study. First, there may be limited room for improvement in ICUs that have daytime intensivist staffing, particularly if the benefits of daytime intensivist staffing derive from better ICU-wide processes of care.9,28 Second, nighttime intensivist staffing may be associated with discontinuity of care for some patients, offsetting benefits for other patients. Third, in the staffing model and setting that we studied, bedside intensivists may not add to the quality of care provided by well-trained resident physicians who have telephone access to intensivists. Finally, nighttime intensivists may truly have an effect on mortality in a small number of patients, but such patients may be so few in number that detecting these benefits would require a much larger study. Future research that investigates these and other potential explanations could inform broader debates about the best ways to use a limited intensivist workforce.29,30

We also found that most residents believed that nighttime intensivists improved their educational experience and provided desirable support for decision making. These findings are tempered by the positive framing of the questions in our survey and the modest response rate. Nonetheless, academic centers may wish to consider residents’ perspectives in choosing to adopt or retain this staffing model.

A strength of this randomized trial is that it took place in an ICU in which 61% of admissions occurred at night. If nighttime intensivists were effective, it is likely that they would be particularly effective in an ICU with such a large nighttime workload. In addition, by randomly assigning weeks rather than individual nights, we ensured that our contrast would meaningfully represent the presence or absence of year-round nighttime intensivist staffing.

An important limitation of this study is that it was performed in a single, academic medical ICU in the United States that had round-the-clock coverage by reasonably well-trained residents. Our results may be generalizable to U.S. academic ICUs with high-intensity daytime staffing, which have been among the early adopters of nighttime intensivist staffing in the United States. However, our study does not address whether nighttime intensivist staffing may provide benefits in community ICUs, ICUs without high-intensity daytime staffing, ICUs with fewer or less well-trained residents, or ICUs in other countries.

Second, our nighttime workforce may differ with respect to age, frequency of shifts, or other characteristics from workforces that are employed or considered elsewhere. It is uncertain whether different nighttime staffing models would affect patient outcomes.

Third, although we evaluated several outcomes, the presence of nighttime intensivists may affect other outcomes such as physician burn-out, staff satisfaction, patient and family experiences, objectively measured educational outcomes, and the incidence of malpractice claims. In addition, outcomes external to the ICU were not measured, such as the possible role of nighttime intensivists in helping hospitals meet quality benchmarks.15

In summary, this randomized trial in an ICU with high-intensity staffing during the day failed to identify benefits to adding intensivists at night. The compelling face validity of nighttime intensivist staffing has probably spurred the widespread adoption of this staffing model.8,10 However, nighttime intensivist staffing may also be one of several expensive medical practices that have been adopted without a supportive evidence base.31 Because the adoption of nighttime intensivist staffing by hospitals with plentiful resources may siphon intensivists away from hospitals with fewer resources,17,18 rigorous evaluation of the model is needed in settings that were not evaluated in this study.

Supported by the University of Pennsylvania Health System and by pilot grants (to Dr. Halpern) from the Roybal Center for Behavioral Economics and Health, National Institute on Aging, National Institutes of Health (P30AG034546), and the Department of Medical Ethics and Health Policy, University of Pennsylvania.

Disclosure forms provided by the authors are available with the full text of this article at NEJM.org.

This article was published on May 20, 2013 at NEJM.org.

http://www.nejm.org/doi/full/10.1056/NEJMoa1302854?query=OF#t=articleDiscussion