Editing APACHE II (section)

==Calculation==
{{Copypaste|date=December 2022}}
The point score is calculated from 12 admission physiologic variables comprising the Acute Physiology Score, the patient's age, and chronic health status:

; A. Acute Physiology Score (measured within 24 hours of admission)
# [[Alveolar–arterial gradient|AaDO2]] or [[PaO2]] (for [[FiO2]]≥0.5 or <0.5, respectively)
# [[body temperature]] (rectal)
# [[mean arterial pressure]]
# [[blood pH]] 
# [[heart rate]]
# [[respiratory rate]]
# [[serum sodium]]
# serum potassium 
# [[creatinine]] (Double point score for acute renal failure)
# [[hematocrit]]
# [[white blood cell count]]
# [[Glasgow Coma Scale]] (15 minus actual GCS)

; B. Age points
{| class="wikitable"
|-
! AGE (yrs)!! Points
|-
| ≤44 || 0
|-
| 45-54 || 2
|-
| 55-64 || 3
|-
| 65-74 || 5
|-
| ≥75 || 6
|}

; C. Chronic health points

If the patient has a history of severe organ system insufficiency (i.e. liver cirrhosis, portal hypertension, [[New York Heart Association Functional Classification|NYHA]] class IV heart failure, severe respiratory disease, dialysis dependent) or is immunocompromised (i.e. due to chemotherapy, radiation, high dose steroid therapy, or advanced leukemia, lymphoma or AIDS) assign points as follows:

:a. for nonoperative or emergency postoperative patients: 5 points
:b. for elective postoperative patients: 2 points

The method is optimized for manual calculation, by using [[integer]] values and limiting 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 subsequently readmitted, a new APACHE II score is calculated.

In the original research paper that described the APACHE II score, patient prognosis (specifically, predicted mortality) was computed based on the patient's APACHE II score in combination with the principal diagnosis at admission.<ref name="pmid3928249"/>