OVERVIEW
- outcome measures are important for research and quality control
- clinically meaningful outcomes measure how patients feel, function or survive, e.g. mortality, quality of life
- surrogate outcomes is a substitute that would be expected to be beneficial based on epidemiological, physiological, therapeutic or other scientific grounds
- unless validated surrogate outcomes should not be used to change clinical practice
ICU MORTALITY
Advantages
- 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 organisational 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
Disadvantages
- Definition of ICU is very hospital specific which can influence mortality (e.g. non-ICU stepdown areas in some hospitals)
- 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 such as 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
HOSPITAL MORTALITY
- Hospital mortality can often be 50% higher than ICU mortality, and is a reasonable surrogate (90%) for 90 days mortality
Advantages
- gets over differences in definition of ICU and ICU discharge thresholds and avoids avoids many problems of censoring at ICU discharge.
- Still a simple and robust endpoint
- easy to obtain from exisiting hospital databases
Disadvantages
- can confound intensive care outcomes with deficiencies in ward or other post ICU care
- Does not address in any way functional outcomes, e.g discharge from hospital to a nursing home in a vegetative state is counted as a positive outcome
90 DAY MORTALITY
Advantages
- simple robust endpoint
- addresses the issue of ongoing mortality after hospital discharge (though this difference is about 10% relative in recent large trials)
- data may be available by linkage with external registries (e.g. Births, Deaths and Marriages)
Disadvantages
- still an arbitrary time point
- 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)
1 YEAR FUNCTIONAL OUTCOME
Advantages
- a ‘POEM’ (patient oriented endpoint that matters)
- Takes into account disability and true long-term consequences of critical illness
Disadvantages
- 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
- Follow up— time consuming, labour intensive, costly face to face vs. phone vs. mail
- Depending on disease may reflect more the natural history of the disease rather than the ICU care per se
Critical Care
Compendium
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