Critical Care

APACHE II Score

ICU severity of illness and mortality risk.

Education and reference only. Not a substitute for clinical judgement, local policy or product labelling. Always verify before clinical use. Values are calculated in your browser and never stored.

When to use

Use within 24 hours of ICU admission to quantify severity of illness and estimate hospital mortality. Use the worst value for each variable in the first 24h.

Why use

It is a long-established ICU severity score used for benchmarking and prognosis.

Temperature (°C)

Mean arterial pressure (mmHg)

Heart rate (/min)

Respiratory rate (/min)

Oxygenation

Arterial pH

Sodium (mmol/L)

Potassium (mmol/L)

Creatinine (mg/dL) — double if acute renal failure

Haematocrit (%)

White cell count (×10³/µL)

Glasgow Coma Scale (points = 15 − GCS)

Age

Chronic health (severe organ insufficiency / immunocompromise)

Critical actions

Use the WORST value in the first 24h. Creatinine points double in acute renal failure (select the higher band manually). Oxygenation uses A-a gradient if FiO₂ ≥0.5, otherwise PaO₂ (mmHg).

Evidence & references

Knaus WA et al. APACHE II: a severity of disease classification system. Crit Care Med. 1985.

About the creator

Knaus WA et al.

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