APACHE II Calculator

APACHE II, the Acute Physiology and Chronic Health Evaluation II, is a severity-of-disease classification system developed for adult intensive care populations. It combines points from abnormal physiologic measurements with age, neurologic status, and selected chronic health conditions. Higher totals describe greater physiologic derangement and, within appropriately matched patient groups, are associated with greater hospital mortality. The score supports population comparison and clinical communication; it does not replace diagnosis, judgment, or an individual treatment plan. The acute physiology component uses the most abnormal values recorded during the first 24 hours after ICU admission. Temperature, mean arterial pressure, heart rate, respiratory rate, oxygenation, arterial pH, sodium, potassium, creatinine, hematocrit, and white blood cell count each contribute zero to four points according to validated ranges. The original model also includes oxygenation rules based on inspired oxygen and may use serum bicarbonate when no arterial blood gas is available. This implementation uses arterial PaO2 and should be applied only when that simplification is appropriate. Neurologic points equal 15 minus the measured Glasgow Coma Scale score. A patient with GCS 15 receives no neurologic points, while lower scores add progressively more. Sedation, paralysis, intoxication, intubation, and preexisting neurologic deficits can make GCS difficult to interpret; clinicians should follow local APACHE data-collection rules. Age adds points beginning at 45 years. Severe chronic organ insufficiency or immunocompromise adds either two or five points depending on whether admission follows elective surgery or is nonoperative or follows emergency surgery. An APACHE II total can range from zero to 71, but mortality cannot be inferred from the total alone. Published mortality estimates depend on diagnostic category, operative status, admission context, calibration period, and the population in which the model is used. Modern outcomes may differ from the original cohort. Values must be confirmed from the clinical record, and any unexpected result should prompt review of units, collection timing, oxygenation method, acute renal failure adjustment, and chronic health eligibility. Use this calculator for education and arithmetic support under qualified critical-care supervision.