🏥 APACHE II Critical Illness Score
APACHE II, an ICU severity-of-illness score combining acute physiology, age, and chronic health to estimate in-hospital mortality.
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).
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When to use
Use within 24 h of ICU admission, taking the worst physiologic values, to benchmark severity and estimate group mortality risk.
How it works
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%).
Key points
- 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.
References
- Knaus WA, et al. APACHE II. Crit Care Med 1985.
- Vincent JL, Moreno R. Scoring systems in the critically ill. Crit Care 2010.
Worked calculation
The values below come from this tool's own example placeholders and are computed server-side with the formula shown on this page, so the arithmetic can be checked quickly. It demonstrates how to substitute values only — it is not clinical advice and not a real case.
| 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 |
| Potassium | 4.0 mmol/L |
| Serum creatinine Scr | 80 μmol/L |
| Acute renal failure (creatinine points doubled) | Yes |
| Hematocrit Hct | 40 % |
| White blood cells | 10 ×10⁹/L |
| GCS | 3 |
| Age | 60 yr |
| Chronic health (organ failure/immunocompromise) | None |
→APACHE II15pts
- Acute Physiology Score (APS)：12
- Age points：3
- In-hospital mortality (approx.)：~25%
| 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 |
| Potassium | 4.0 mmol/L |
| Serum creatinine Scr | 80 μmol/L |
| Acute renal failure (creatinine points doubled) | No |
| Hematocrit Hct | 40 % |
| White blood cells | 10 ×10⁹/L |
| GCS | 3 |
| Age | 60 yr |
| Chronic health (organ failure/immunocompromise) | Yes · elective postoperative (+2) |
→APACHE II17pts
- Acute Physiology Score (APS)：12
- Age points：3
- Chronic-health points：2
Frequently asked questions
- What is APACHE II Critical Illness Score?
- APACHE II, an ICU severity-of-illness score combining acute physiology, age, and chronic health to estimate in-hospital mortality.
- How is APACHE II Critical Illness Score calculated? What is the core formula?
- 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%).
- When is APACHE II Critical Illness Score used?
- Use within 24 h of ICU admission, taking the worst physiologic values, to benchmark severity and estimate group mortality risk.
- What are the key clinical points for APACHE II Critical Illness Score?
- 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.
- What are the limits and cautions when using APACHE II Critical Illness Score?
- 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.
- How is APACHE II Critical Illness Score calculated in practice? Can you show a worked example?
- 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）