1APACHE II — ICU Mortality Reference
| APACHE II Score | Non-Operative | Post-Operative | Severity |
|---|---|---|---|
| 0–4 | 4% | 1% | Low |
| 5–9 | 8% | 3% | Low–Moderate |
| 10–14 | 15% | 7% | Moderate |
| 15–19 | 25% | 12% | Moderate–High |
| 20–24 | 40% | 30% | High |
| 25–29 | 55% | 35% | High |
| 30–34 | 73% | 73% | Very High |
| ≥35 | >85% | >85% | Critical |
APACHE II — Clinical Context
APACHE II was developed by Knaus et al. (1985) from data on 5,815 ICU admissions across 13 US hospitals. It remains one of the most widely used and externally validated ICU severity scores globally. The score is calculated from the worst physiological values recorded in the first 24 hours of ICU admission, reflecting the severity of acute illness at its worst. Age and chronic health status add independent prognostic weight.
APACHE II is used for: ICU performance benchmarking, research stratification, quality improvement, resource allocation decisions, and family counselling regarding prognosis. It should NOT be used as the sole determinant for treatment limitation decisions, which require full multidisciplinary assessment and patient/family consultation.
APACHE II Limitations
- Derived from 1979–1982 data — overestimates mortality in modern ICUs due to improved treatment
- Does not account for lead-time bias or pre-ICU treatment
- Poorly calibrated for some diagnoses (burns, post-cardiac arrest, liver failure)
- APACHE IV and SOFA have largely replaced APACHE II in research; APACHE II remains widely used clinically
2Frequently Asked Questions
APACHE II provides an objective assessment of ICU admission severity using acute physiology, age, and chronic health, serving as a reliable benchmark for expected mortality and resource allocation.
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Medical disclaimer: This calculator is for educational and clinical decision-support purposes only. It does not replace clinical judgment or specialist consultation. RxMedCalc is not liable for clinical decisions made solely on this tool.