Calculator Inputs
Enter the worst values observed during the first 24 hours of ICU care.
Example Data Table
| Patient Snapshot | Example Value | Points |
|---|---|---|
| Temperature | 39.2 °C | 3 |
| Mean arterial pressure | 62 mm Hg | 2 |
| Heart rate | 128 bpm | 2 |
| Respiratory rate | 30 breaths/min | 1 |
| PaO₂ | 58 mm Hg | 3 |
| Arterial pH | 7.28 | 2 |
| Serum sodium | 149 mmol/L | 0 |
| Serum potassium | 3.2 mmol/L | 1 |
| Serum creatinine | 1.8 mg/dL | 2 |
| Hematocrit | 33% | 0 |
| White blood cells | 18 ×10³/µL | 1 |
| GCS | 11 | 4 |
| Age points | 67 years | 5 |
| Chronic health points | Nonoperative with severe chronic disease | 5 |
| Total | Example APACHE II score | 31 |
Formula Used
APACHE II Score = Acute Physiology Score + Age Points + Chronic Health Points
The acute physiology score is the sum of 12 weighted variables: temperature, mean arterial pressure, heart rate, respiratory rate, oxygenation, acid-base status, sodium, potassium, creatinine, hematocrit, white blood cell count, and Glasgow Coma Score.
GCS Points = 15 − actual GCS
For oxygenation, use PaO₂ when FiO₂ is below 0.50 and A-aDO₂ when FiO₂ is 0.50 or higher. When arterial blood gases are unavailable, serum bicarbonate can replace arterial pH. If acute renal failure is present, the creatinine point value is doubled.
How to Use This Calculator
- Collect the worst vital sign and laboratory values from the first 24 hours.
- Choose the correct oxygenation pathway based on the patient’s FiO₂ level.
- Enter either arterial pH or serum bicarbonate, depending on available data.
- Enter the three Glasgow Coma Scale components to generate GCS points.
- Select the admission type and mark severe chronic disease when applicable.
- Mark acute renal failure only when the creatinine rule should be doubled.
- Press Calculate Score to display the result above the form.
- Use the CSV or PDF buttons to export the breakdown for review.
Frequently Asked Questions
1. What does the APACHE II score measure?
It summarizes acute physiologic disturbance, age impact, and chronic health burden. Higher totals generally reflect greater illness severity during early ICU assessment.
2. Which values should I enter?
Use the worst values recorded during the first 24 hours of ICU care. This follows the standard APACHE II scoring approach.
3. When should I use PaO₂ instead of A-aDO₂?
Use PaO₂ when FiO₂ is below 0.50. Use A-aDO₂ when FiO₂ is 0.50 or higher.
4. Can bicarbonate replace arterial pH?
Yes. Serum bicarbonate can be used when arterial blood gas data are unavailable. Only one acid-base pathway should be scored.
5. Why are GCS component fields included?
Eye, verbal, and motor subscores make data entry more structured. The calculator adds them and converts the total into APACHE II GCS points.
6. How do chronic health points work?
If severe organ insufficiency or immunocompromise is present, elective postoperative patients receive 2 points. Nonoperative and emergency postoperative patients receive 5 points.
7. Does this tool estimate mortality exactly?
No. This version focuses on score calculation and structured interpretation. Real-world prognosis depends on diagnosis, context, and clinical judgment.
8. Should this calculator replace bedside decision-making?
No. It is an educational and documentation aid. Final assessment should always come from qualified clinicians using the full patient picture.