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ICU and 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.

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.

Result

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Clinical inputs

  • Rectal temperature (°C)
  • Mean arterial pressure (mmHg)
  • Heart rate (/min)
  • Respiratory rate (/min)
  • Oxygenation
  • Arterial pH (or serum HCO₃⁻ if no ABG)
  • Serum sodium (mmol/L)
  • Serum potassium (mmol/L)
  • Serum creatinine (mg/dL)
  • Acute renal failure (double creatinine points)
  • Hematocrit (%)
  • White blood cell count (×10³/mm³)
  • Glasgow Coma Scale contribution (15 − measured GCS)
  • Age points
  • Severe chronic health condition

Primary source

Knaus WA, Draper EA, Wagner DP, Zimmerman JE. APACHE II: a severity of disease classification system. Crit Care Med. DOI: 10.1097/00003246-198510000-00009. PMID: 3928249. Scope: APACHE II = Acute Physiology Score (12 physiologic variables with published point ladders, including doubled creatinine points in acute renal failure) + age points + chronic health points (0/2/5); total 0–71 using worst values in the first 24 ICU hours. (1985)

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