Reviewed and revised 26 August 2015
Appropriate outcome measures is vitally important in ICU research
Types of outcomes
- ICU mortality
- hospital mortality
- 90 day mortality
- 1 year functional outcome
- simple, single metric
- concrete endpoint which is already available in hospital databases
- death is an important endpoint
- aggregation of a large number of diagnoses with a small number in each increases power to detect variation
- variation over time may reflect institutional and organizational events or characteristics- budget cuts, bed pressure etc. and be able to detect true quality deficiencies
- May be useful when combined as part of an overall quality program
- Definition of ICU is very hospital specific which can influence mortality (e.g. non-ICU step-down areas in some hospitals)
- As a consequence can be ‘gamed’ e.g. transfers out to die in the ward or other units
- Poor correlation between mortality and quality of care in some diagnoses – alternatives available e.g. diagnosis specific risk models e.g. EuroSCORE for CABG, APACHE SMR, trauma scores. Can mask problems in low volume diagnostic groups
- Difficult to draw hospital comparisons and or allow league table construction
- False conclusions can be drawn unless robust statistical methods used
Compared to ICU mortality, avoids many problems of censoring at ICU discharge. Hospital mortality can often be 50% higher than ICU mortality, and is a reasonable surrogate (90%) for 90 days mortality.
- gets over differences in definition of ICU and ICU discharge thresholds.
- Still a simple and robust endpoint which is easy to obtain from existing hospital databases.
- can confound intensive care outcomes with deficiencies in ward or other post ICU care.
- Does not address in any way functional outcomes [so discharge from hospital to a nursing home in a vegetative state is counted as a positive outcome]
90 DAY MORTALITY
Simple robust endpoint which addresses the issue of ongoing mortality after hospital discharge (though this difference is about 10% relative in recent large trials).
- simple robust endpoint
- data may be available by linkage with external registries (e.g. Births, Deaths and Marriages)
- still an arbitrary time point [while 28 days is clearly inadequate, 90 days may still be insufficient to accurately measure the attributable mortality from an episode of critical illness]
- Problems with loss to follow up after ICU discharge.
- Ethical implications of contacting patients after discharge (especially for research studies).
ONE YEAR FUNCTIONAL OUTCOME
- a ‘POEM’ (patient oriented endpoint that matters)
- Takes into account disability and true long-term consequences of critical illness.
- no ideal scoring tool available – existing tools all have problems; some measure particular functional domains well
- problems with face validity
- All functional outcome measures are time consuming to apply
- Problems with loss to follow up
- Time consuming, labour intensive, costly face to face vs. phone vs. mail follow up
- Depending on disease may reflect more the natural history of the disease rather than the ICU care per se
Chris is an Intensivist and ECMO specialist at the Alfred ICU in Melbourne. He is also a Clinical Adjunct Associate Professor at Monash University. He is a co-founder of the Australia and New Zealand Clinician Educator Network (ANZCEN) and is the Lead for the ANZCEN Clinician Educator Incubator programme. He is on the Board of Directors for the Intensive Care Foundation and is a First Part Examiner for the College of Intensive Care Medicine. He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives.
After finishing his medical degree at the University of Auckland, he continued post-graduate training in New Zealand as well as Australia’s Northern Territory, Perth and Melbourne. He has completed fellowship training in both intensive care medicine and emergency medicine, as well as post-graduate training in biochemistry, clinical toxicology, clinical epidemiology, and health professional education.
He is actively involved in in using translational simulation to improve patient care and the design of processes and systems at Alfred Health. He coordinates the Alfred ICU’s education and simulation programmes and runs the unit’s education website, INTENSIVE. He created the ‘Critically Ill Airway’ course and teaches on numerous courses around the world. He is one of the founders of the FOAM movement (Free Open-Access Medical education) and is co-creator of litfl.com, the RAGE podcast, the Resuscitology course, and the SMACC conference.
His one great achievement is being the father of three amazing children.
On Twitter, he is @precordialthump.