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
What is APACHE II used for?
APACHE II (Acute Physiology and Chronic Health Evaluation II) estimates ICU mortality risk using 12 acute physiological variables, age, and chronic health status. Scores range 0–71. It is used for ICU benchmarking, clinical research stratification, prognosis estimation, and family discussions — not for individual treatment-limitation decisions.
What APACHE II score predicts high mortality?
Score 0–9: <10% mortality. Score 10–19: 15–25%. Score 20–24: ~40%. Score 25–29: ~55%. Score 30–34: ~73%. ≥35: >85%. These are population estimates. Actual mortality depends on diagnosis, ICU interventions, and centre-level factors.
What are the 12 physiological variables in APACHE II?
Temperature (rectal), mean arterial pressure, heart rate, respiratory rate, oxygenation (A-a gradient or PaO2), arterial pH, serum sodium, serum potassium, creatinine, haematocrit, white cell count, and GCS. Each scored 0–4 based on deviation from normal using worst values in first 24 ICU hours.
What chronic conditions add APACHE II points?
5 points added for non-operative or emergency surgical patients with: liver cirrhosis with portal hypertension, NYHA Class IV heart failure, severe COPD/chronic hypoxia, chronic renal replacement therapy, or immunosuppression (chemotherapy, steroids, AIDS). 2 points for elective surgical patients with same conditions.
How does APACHE II compare to SOFA?
APACHE II is calculated once at ICU admission — it is a severity-at-admission score. SOFA is calculated daily to track organ failure trajectory. A rising SOFA predicts poor outcome better than a high initial APACHE II. Use APACHE II for admission severity; SOFA for daily monitoring and sepsis definition.
Is APACHE II validated in Indian ICUs?
APACHE II has been validated in multiple Indian ICU studies and performs reasonably well, though it tends to overestimate mortality in Indian populations compared to the original Western derivation cohort. Several Indian studies suggest calibrating with local mortality data. Despite this, it remains the most widely used ICU severity score in India.
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.