The Apache-II Score provides an estimate of ICU mortality based on a number of laboratory values and patient signs taking both acute and chronic disease into account. Note: The data used should be from the initial 24 hours in the ICU, and the worst value (furtherest from baseline/normal) should be used. The following defines "chronic organ insufficiency" and immunocompromise:

• Liver insufficiency
• Biopsy proven cirrhosis
• Documented portal hypertension
• Episodes of past upper GI bleeding attributed to portal hypertension
• Prior episodes of hepatic failure / encephalopathy / coma.
• Cardiovascular
• New Heart Association Class IV Heart Failure
• Respiratory
• Chronic restrictive, obstructive or vascular disease resulting in severe exercice restriction, i.e. unable to climb stairs or perform household duties.
• Documented chronic hypoxia, hypercapnia, secondary polycythemia , severe pulmonary hypertension (> 40 mmHg), or respirator dependency.
• Renal
• Receiving chronic dialysis
• Immunosuppression
• The patient has received therapy that suppresses resistance to infection e.g. immuno-suppression, chemotherapy, radiation, long term or recent hight dose steroids, or has a disease that is sufficiently advanced to suppress resistance to infection, e.g. leukemia, lymphoma, AIDS.

Knaus WA, Draper EA, Wagner DP, Zimmerman JE. APACHE II: a severity of disease classification system.