Critical Care

APACHE II calculator

Enter the published formula inputs below to calculate and interpret this score.

Clinical inputs

Rectal temperature (°C)

Mean arterial pressure (mmHg)

Heart rate (/min)

Respiratory rate (/min)

Oxygenation

Use PaO₂ when FiO₂ <0.50; use alveolar–arterial oxygen difference when FiO₂ ≥0.50.

Arterial pH (or serum HCO₃⁻ if no ABG)

Use arterial pH when available. The labels also show the published serum bicarbonate substitute.

Serum sodium (mmol/L)

Serum potassium (mmol/L)

Serum creatinine (mg/dL)

Double the acute-physiology creatinine points when acute renal failure is present.

Acute renal failure (double creatinine points)

Hematocrit (%)

White blood cell count (×10³/mm³)

Glasgow Coma Scale contribution (15 − measured GCS)

APACHE II neurologic points equal 15 minus the measured GCS; assess before sedation when possible.

Age points

Severe chronic health condition

Applies to severe organ-system insufficiency or immunocompromise documented before this admission.

Complete all required inputs to calculate the score.

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