Arulkumaran N, Harrison DA and Brett SJ
British Journal of Anaesthesia 2017;118 (1): 112-22.
Aim of Study
- Does the day and time of admissions to ICU influence overall mortality?
- ICU must operate as a 24/7 speciality so answering the question of the existence of the weekend effect is an important clinical investigation.
- It is imperative to ascertain whether out-of-hours services are adequate to cover emergency care without any adverse impact on outcome for patient
Design and Location
- Prospectively collated cohort study
- Data from UK Intensive Care National Audit and Research Centre (ICNARC) Case Mix Programme (CMP) database
- Not including specialist units (neuro, cardiac) nor standalone HDU
- Day split into “routine hours” (0800-1759) and “out of hours” (1800-0759)
- Missing physiological data presumed normal
- Potential confounders identified in advance and adjusted for in analysis:
- Age
- Severe conditions in past medical history
- Prior functional dependency
- Number of days from hospital admission to critical care admission
- location before admission
- CPR in 24 hours prior to critical care admission
- Primary reason of admission to critical care
- Acute severity of illness score (ICNARC and APACHE scores used)
- Stats:
- 3 multilevel logistic regression models used:
- Unadjusted with single covariant of day/time of admission
- Adjusted model adjusting for key potential confounders:
- Adjusted model including delay/no delay covariate
- 216 General/mixed Intensive Care Units in the UK that submitted data for the ICNARC CMP
- April 1 2013-March 31st 2015
Methodology
Population
- Inclusions:
- Age >16
- Unplanned admission
- Exclusions:
- Planned ICU admission (including post theatre, transfers and repatriation)
- Readmissions – only the first episode was counted
- Organ donation
- Missing data (primary outcome or key confounders)
- 300,469 admission screened, 195,428 included in final analysis
- Baseline characteristics:
- mean age of patients admitted was 60 yr
- mean APACHE II = 17
- ~1/4 had some degree of prior dependency
- Overall, 4% of patients received in-hospital CPR during the 24 h before admission and a further 4% had out-of-hospital CPR
- ~1/4 admitted with respiratory pathology
- No significant differences between the two cohorts seen in any of the major criteria, including age, severity of illness, and co-morbidities
Weekend days cohort
- Day of admission analysis: Patients admitted on Saturday or Sunday
- Time of admission analysis: During routine working hours (0800-1759) and out of (1800 0759)
Week days cohort
- Day of admission analysis: Patients admitted on Monday, Tuesday, Wednesday, Thursday or Friday
- Time of admission analysis: During routine working hours (0800-1759) and out of (1800 0759)
- Primary outcome:
- Total ICU mortality: 18.8%
- Total hospital mortality: 26.6%
- Using Monday as reference day, no significant difference seen between odds of admission out of hours or at a weekend in adjusted analysis (P value =0.61)
- Secondary outcome:
- 8,295 (4.2%) patients experienced a delay (documented decision to admit to time of admission) of at least 1 hour prior to admission to ICU. 2,097 (1.1%) had delay >4hrs
- Both groups associated with an increased risk of death (OR 1.08 for < 4hrs, 1.17 for >4 hrs, P=0.04)
- Adjusting to account for delay did not change lack of effect of day/time of admission
- 8,295 (4.2%) patients experienced a delay (documented decision to admit to time of admission) of at least 1 hour prior to admission to ICU. 2,097 (1.1%) had delay >4hrs
Statistics
multilevel logistic regression models.
The output of each model is presented as odds ratios with 95% confidence intervals (CIs) and P-values.
Hypothesis testing.
Results of the hypothesis tests are reported as the P-value (Wald test) and the absolute risk difference with 95% CI (based on linear combinations of the marginal predicted mortalities).
Conclusions/Discussions
- After risk adjustment with detailed clinical data, there was no difference in acute hospital mortality for unplanned admissions to ICU between weekdays and weekends, or daytime and nighttime
- A small proportion of patients experienced delays in admission to ICU and this was associated with an increased risk of death
Stated Limitations from the Study
Strengths
- Important question
- Large database
- Multi centre
- Detailed risk adjusted analysis
- Secondary analysis an important question
- clinicaltrials.gov
Weaknesses
- Without delving into the inner workings of each ICU, shows association not causation
- Difference exists between units in the ICNARC CMP
- Delayed admission is a complex entity; may represent increased complexity of patient and further investigations or treatments.
- UK based study
Discussion from Journal Club Meeting (?Change of Practice)
Ensure no delay to admissions to ICU
Ensure access to ICU specialist consultant at all times
Summary by Dr W Turner. Journal Club 22 February 2018.