APACHE II Critical Illness Score — free guideline decision tool

APACHE II, an ICU severity-of-illness score combining acute physiology, age, and chronic health to estimate in-hospital mortality.

Acute Physiology Score (12 items) + age points + chronic-health points (0–71); rising totals map to higher predicted mortality (e.g. 0–4 ~4%, 15–19 ~25%, 25–29 ~55%, > 34 ~85%).

Use within 24 h of ICU admission, taking the worst physiologic values, to benchmark severity and estimate group mortality risk.

APACHE II is a population benchmark, not an individual outcome predictor — never use it to decide a single patient's prognosis (original synthesis · not guideline verbatim). Use the worst value within the first 24 h for each variable; mixing time points distorts the score. The creatinine points double in acute renal failure, reflecting the added severity of AKI.

For licensed clinicians and clinical researchers. Interpret results with history, investigations and local protocols; not a diagnosis or prescription, and not a substitute for multidisciplinary decision-making or local guidelines.

Inputs: Temperature (core) 37 ℃, Mean arterial pressure MAP 90 mmHg, Heart rate 90 bpm, Respiratory rate 18 /min, FiO₂ < 0.5 (enter PaO₂), Oxygenation: PaO₂ or A-aDO₂ 80 mmHg, Arterial pH 7.40, Sodium 140 mmol/L… → Result: APACHE II 15 pts（Acute Physiology Score (APS): 12, Age points: 3, In-hospital mortality (approx.): ~25%） Inputs: Temperature (core) 37 ℃, Mean arterial pressure MAP 90 mmHg, Heart rate 90 bpm, Respiratory rate 18 /min, FiO₂ ≥ 0.5 (enter A-aDO₂), Oxygenation: PaO₂ or A-aDO₂ 80 mmHg, Arterial pH 7.40, Sodium 140 mmol/L… → Result: APACHE II 17 pts（Acute Physiology Score (APS): 12, Age points: 3, Chronic-health points: 2）