Does this give a predicted mortality percentage?

No. A precise APACHE II predicted-mortality percentage requires the admission diagnosis–specific coefficient, which varies by condition. This calculator shows the validated score and an approximate, group-level risk band rather than inventing a patient-specific percentage.

Which values should I enter?

Use the worst physiological values in the first 24 hours of ICU admission for each variable, as in the original definition.

When do I use A-aDO₂ versus PaO₂ for oxygenation?

Use the alveolar–arterial oxygen gradient (A-aDO₂) when FiO₂ is 0.5 or higher, and PaO₂ when FiO₂ is below 0.5 — the calculator scores whichever you select.

What raises the creatinine points?

In the presence of acute renal failure, the creatinine points are doubled. Toggle the acute-renal-failure control to apply that.

APACHE II Score Calculator — ICU Severity & Mortality Risk

Acute Physiology and Chronic Health Evaluation II — twelve physiology variables, plus age and chronic-health points, from the worst values in the first 24 hours. Every point is shown in the breakdown.

What APACHE II is

APACHE II (Acute Physiology and Chronic Health Evaluation II) is a severity-of-illness classification for adult ICU patients. It combines an Acute Physiology Score (twelve variables), age points and chronic-health points into a total from 0 to 71, computed from the worst values in the first 24 hours of admission.

When to use it

APACHE II is used within 24 hours of ICU admission for severity stratification, cohort benchmarking and research. It describes a population; it is not a bedside tool for individual treatment decisions.

How it is calculated

Acute Physiology Score — temperature, MAP, heart rate, respiratory rate, oxygenation (A-aDO₂ if FiO₂ ≥ 0.5, else PaO₂), arterial pH, sodium, potassium, creatinine, hematocrit, WBC, and GCS.
GCS contributes 15 − GCS (not banded).
Creatinine points are doubled in acute renal failure.
Age: ≤44 → 0 · 45–54 → +2 · 55–64 → +3 · 65–74 → +5 · ≥75 → +6.
Chronic health (if severe organ insufficiency or immunocompromise): nonoperative or emergency post-op → +5; elective post-op → +2.

Interpretation

Approximate, group-level bands: 0–9 low · 10–19 moderate · 20–29 high · ≥ 30 very high (roughly > 50% predicted in-hospital mortality). This tool deliberately shows the score and a band rather than a precise predicted-mortality percentage, because that figure requires an admission-diagnosis-specific coefficient and must not be invented.

Limitations

Requires the worst first-24h values; misuse of the time window changes the result.
A precise predicted mortality needs a diagnosis coefficient not included here — bands are approximate and population-level, not patient-specific.
Newer models (APACHE III/IV, SAPS II/III) exist; APACHE II remains widely used and cited.

References

Knaus WA, Draper EA, Wagner DP, Zimmerman JE. APACHE II: a severity of disease classification system. Crit Care Med. 1985;13(10):818–829.

Related scores

UltraCare

This is one instrument on a much larger chart.

Inside the UltraCare workspace, APACHE II recomputes itself on every charted value — alongside SOFA, qSOFA, NEWS2, deterioration signals and I-PASS handovers, admission to discharge. The clinician stays in the loop.

Request a pilot See the workspace