APACHE II

APACHE II ("Acute Physiology and Chronic Health Evaluation II") is a severity-of-disease classification system (Knaus et al., 1985), one of several ICU scoring systems. It is applied within 24 hours of admission of a patient to an intensive care unit (ICU): an integer score from 0 to 71 is computed based on several measurements; higher scores correspond to more severe disease and a higher risk of death. The first APACHE model was presented by Knaus et al. in 1981.

APACHE II was designed to measure the severity of disease for adult patients admitted to intensive care units. It has not been validated for use in children or young people aged under 16.

This scoring system is used in many ways which include:

Even though newer scoring systems, such as SAPS II, have replaced APACHE II in many places, APACHE II continues to be used extensively because so much documentation is based on it.

The point score is calculated from a patient's age and 12 routine physiological measurements:

These were measured during the first 24 hours after admission, and utilized in additional to information about previous health status (recent surgery, history of severe organ insufficiency, immunocompromised state) and baseline demographics such as age. The calculation method is optimized for paper schemas, by using integer values and reducing the number of options so that data fits on a single-sheet paper form.

The score is not recalculated during the stay; it is by definition an admission score. If a patient is discharged from the ICU and readmitted, a new APACHE II score is calculated.

In the original research paper that described the APACHE II score (see references), patient prognosis (specifically, predicted mortality) was computed based on the patient's APACHE II score in combination with the principal diagnosis at admission.

A method to compute a refined score known as APACHE III was published in 1991.

The score was validated on the dataset from 17,440 adult medical/surgical intensive care unit (ICU) admissions at 40 US hospitals.

The prognostic system of APACHE III has two options:

This provides an initial risk classification of severely ill hospitalized patients in defined groups.

This uses APACHE III Score with a number of additional variables including the primary reason for ICU admission (from a reference list of 212 conditions classified according to etiology, major organ involved, and distinction between surgical/medical categories); age, sex, race and preexisting comorbidities; and location prior to ICU admission (operating room, recovery or emergency room, transfer or readmission from another hospital or ICU).

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