ICU Outcomes

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