APACHE II ("Acute Physiology and Chronic Health Evaluation II") is a severity-of-disease classification system, 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. Application 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: Some procedures or some medicine is only given to patients with a certain APACHE II score APACHE II score can be used to describe the morbidity of a patient when comparing the outcome with other patients. Predicted mortalities are averaged for groups of patients in order to specify the group's morbidity. Even though newer scoring systems, such as APACHE III, have replaced APACHE II in many places, APACHE II continues to be used extensively because so much documentation is based on it. Calculation 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) 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 C. Chronic health points If the patient has a history of severe organ system insufficiency (i.e. liver cirrhosis, portal hypertension, 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