Hospital mortality associated with day and time of discharge from intensive care units in the United Kingdom

Background

The day and time of admission to the ICU does not affect subsequent hospital mortality in the United Kingdom after adjustment for severity of illness [1]. An independent editorial published alongside this study [2], commented that "time and day of discharge from the ICU may have an even greater impact on patient outcomes" because of reduced staffing levels and services on the wards at weekends and at night.

Aim

To investigate whether day or time of discharge is associated with subsequent hospital mortality.

Design

A retrospective cohort study.

Setting

One hundred and seventy-two adult general (medical/ surgical) ICUs in England, Wales and Northern Ireland participating in the Case Mix Programme.

Population

A total of 174,361 consecutive admissions between December 1995 and June 2004 discharged alive from the ICU to a ward in the same hospital (not for palliative care).

Analysis

The day of the week, defined a priori, commenced at 08:00 hours on one day to 07:59 hours the following day. Each weekday was spilt into three time periods: day 08:00–17:59 hours; evening 18:00–23:59 hours; and night 00:00–07:59 hours. Crude and case mix adjusted hospital mortality were calculated for the day of the week and the time of day of discharge from the ICU.

Results

After exclusions for APACHE II, 144,210 admissions to 172 ICUs were included in the analysis. Most patients were discharged during the day (n = 113,595, 79%) compared with evening (n = 26,345, 18%) and night (n = 4270, 3%). Discharges were lowest on Sunday (n = 13,638) and highest on Friday (n = 25,069). Selecting Wednesday (day of week) and day (time of day) as reference, discharge on Sunday or Monday was associated with higher crude hospital mortality compared with Wednesday (Sunday odds ratio [OR] 1.12, 95% confidence interval [CI] 1.04–1.20; Monday OR 1.19, 95% CI 1.11–1.26). These were no longer significant after adjusting for case mix (Sunday OR 1.04, 95% CI 0.96–1.13; Monday OR 1.02, 95% CI 0.96–1.09). Discharge in the evening and at night was associated with higher crude hospital mortality compared with day (evening OR 1.37, 95% CI 1.32–1.43; night OR 1.47 95% CI 1.34–1.61), which was still significant after adjusting for case mix (evening OR 1.22, 95% CI 1.16–1.28; night OR 1.34, 95% CI 1.20–1.50).

Conclusion

Hospital mortality is not associated with day of the week of discharge from the ICU but is associated with time of day of discharge. As previously reported, this is partly due to premature discharges from the ICU occurring more frequently in the evening and/or at night [3], but may also be due to discharged patients not receiving the appropriate level/amount of care on the wards at these times, possibly due to reduced staffing levels. Further investigation is warranted.