APACHE II Calculator

The Acute Physiology and Chronic Health Evaluation II (APACHE II) score is one of the critical care scoring systems, developed in 1981.

Clinicians and health professionals worldwide use this system to assess the severity of a disease and the risk of death of an intensive care unit patient within the first 24 hours of admission.

The system allows us to apply the most suitable treatment and compare the morbidity and outcomes of different patients.

Try out our SAPS II calculator to learn more about the popular critical care scoring systems.

In this section, we'll explain all the details needed to properly evaluate the APACHE 2 score and get the patient's predicted mortality.

The APACHE II calculator requires you to fill 16 empty fields, divided into three categories:

• Patient's characteristics;
• Present on examination; and
• Laboratory test results.

❗ Remember to fill in all the fields. You will not obtain your results until you provide all the informations needed

Here are the inputs in detail:

1. Age – the APACHE II score is meant for people over 16 years of age.

2. History of severe organ insufficiency:

   • If yes, did your patient require surgery? Choose between an elective and emergency operation.

   • You may also choose a non-surgical treatment for patients who suffered severe trauma but were not treated surgically.

   List of possible chronic organ insufficiencies:

   • NYHA IV – New York Heart Association Class IV heart failure;

   • Chronic dialysis;

   • Liver cirrhosis and its consequences – e.g., portal hypertension, esophageal bleeding, or encephalopathy; and

   • Immunocompromised patients – includes treatment such as chemotherapy and radiotherapy and diseases such as leukemia and AIDS.

3. Renal failure – evaluate the function of the kidneys.

   The physicians must use their clinical judgment to determine whether the patient suffers from acute or chronic renal failure.

4. Temperature – can be given in either metric or imperial units.

5. Glasgow Coma Scale – points should consist between 3 and 15 (see Glasgow Coma Scale calculator).

6. Mean Arterial pressure (MAP) - can be calculated using the following formula:

   MAP = 1/3 × (Systolic Blood Pressure) + 2/3 × (Diastolic Blood Pressure).

7. Heart rate – is given in beats per minute. (The best way to calculate this is to count the number of beats over 15 seconds and then multiply the result by 4.)

8. Respiratory rate – count your patient's breaths over 1 minute.

9. Oxygenation – FiO₂ level:

   • If your patient's FiO₂ is above or equal to 50%, use the A-a gradient in the next step (see A-a gradient calculator); or

   • If your patient's FiO₂ is below 50%, use the PaO₂ (partial pressure of oxygen – see partial pressure calculator).

10. Hematocrit – ideally, the percentage of red blood cells in the blood should consist between 36-51%.

11. White blood cells – ideally given in thousands per cubic milliliter. A number above 10,000 indicates an ongoing infection or severe trauma.

12. Arterial blood pH – should ideally be between 7.33-7.5.

13. Potassium and sodium levels can be given in either millimole per liter (mmol/L) or milliequivalent per liter (mEq/L). In this case, 1 mmol/L = 1 mEq/L.

14. Creatinine – also evaluates the function of the kidneys.

Creatinine can be evaluated in milligrams per deciliter (mg/dL) or micromoles per liter (μmol/L).

You might also be interested in our general mortality rate calculator.

This section will provide you with the number of points given for each category of the APACHE II score.

The patient's characteristics

On examination

Laboratory test results