APACHE II Score Calculator

How it is calculated

The score is APACHE II = APS + age points + chronic health points. The Acute Physiology Score (APS) is the sum of points from 12 readings: temperature in °C, mean arterial pressure in mmHg, heart rate and respiratory rate per minute, oxygen (PaO₂ in mmHg), arterial pH, sodium and potassium in mmol/L, creatinine in mg/dL, hematocrit in %, white cell count in thousands per mm³, and Glasgow Coma Scale, which adds 15 − GCS points. Each reading falls into a band worth 0 to 4 points; the middle band is 0. A band runs from its lower limit up to the next band's lower limit, so a reading between two printed edges (such as 38.95 °C) scores like the band below it (1 point, as 38.5 to under 39). Age adds 0 to 6 points. Chronic health adds 5 points for non-operative or emergency admissions and 2 for elective surgery; anything else counts as 0. Mortality is estimated with ln(R/(1−R)) = −3.517 + 0.146 × score. The oxygen band uses PaO₂ only, so it suits patients on room air. This is a teaching estimate, not a clinical decision.

Common mistakes

• Using the latest values instead of the worst values from the first 24 hours; the score is meant to capture the most deranged reading of each variable.
• Entering FiO₂ or an A-aDO₂ value in the oxygen field; the tool expects PaO₂ in mmHg and a high number simply scores 0.
• Entering creatinine in µmol/L; the field is in mg/dL, so a value like 150 would give maximum points.
• Entering the Glasgow Coma Scale as the deficit instead of the score; enter 3 to 15, where 15 is fully alert.
• Entering the temperature in °F or the MAP as systolic pressure; both would land in the wrong bands.