Outline the principles of illness severity scoring systems used in the critically ill patient, and using examples outline their relationship to clinical outcome.
Scoring systems stratify groups of critically ill patients by severity, compare groups of patients in research trials, compare ICUs, and predict mortality for individuals and groups. Most measure physiological variables, some measure interventions. Derived by logistic regression from large demographic data sets of critically ill patients. Commonly used systems include:
• APACHE II. Commonly used in Australia to measure patient severity. Uses 12 physiological variables and previous health estimate. Requires measure of worst values in first 24 hours in ICU, so affected if ICU admission delayed. Not reliable for predicting outcome in individuals. Limited by derivation from an historical data set.
• APACHE III. Better outcome predictions by using additional variables and a more recent data set for comparisons. Outcome predictions for Australian patients more accurate.
• GCS. Used to quantify severity of coma. Scale from 3-15. Eye (1-4), Verbal (1-5), and Motor (1-6) components. Key score for outcome prediction after head injury. Affected by alcohol and sedation. Should be scored in non-sedated non-paralysed patients. Important component of other scoring systems eg APACHE 11.
• TISS. System to score patient severity by counting procedures done. Less widely used.
Physician dependent, so less useful to compare ICUs.
• SOFA. Organ dysfunction scores. Often a secondary endpoint in research trials.
Here is a link to the LITFL article on ICU scoring systems.
Here are some links to the seminal articles which describe these systems:
How are these scoring systems useful?
APACHE stands for Acute Physiology, Age and Chronic Health Evaluation (I-IV).
SOFA stands for Sequential Organ Failure Assessment .
There is a defined score of 1-4 for each organ system, which is collected daily. This not a predictive model- there are no mortality algorithms here. A higher SOFA score can be said to relate to increased mortality, but there is no mathematical model to help us figure out exactly how the total score relates to survival.
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