APACHE II Calculator

Created by Łucja Zaborowska, MD, PhD candidate
Reviewed by Bogna Szyk and Jack Bowater
Last updated: Nov 29, 2022

The APACHE II calculator allows you to compute the intensive care unit (ICU) mortality rates for nonoperative and postoperative patients using their medical history, characteristics, physical examination, and laboratory test results.

Follow the article below to learn what is the APACHE II score, more about the APACHE score for ICU, and its possible medical applications.

Read on – we will also cover the essential rules for assessing a patient's state and comorbidities according to the APACHE scoring system. 🧪

What is the APACHE II score?

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.

How to use the APACHE II calculator?

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. OxygenationFiO₂ level:

  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.

How to calculate APACHE II score?

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

The patient's characteristics

Age (years)

No. of points

≤44

0

45-54

2

55-64

3

65-74

5

>74

6

History of severe organ insufficiency/ immunocompromised patient

Yes: nonoperative/ emergency postoperative patient

5

Yes: elective postoperative patient

2

No

0

On examination

Rectal temperature (°C)

No. of points

≥41

4

39 to <41

3

38.5 to <39

1

36 to <38.5

0

34 to <36

1

32 to <34

2

30 to <32

3

<30

4

Glasgow Coma Scale (GCS score)

3-15

15

Mean arterial pressure (mmHg)

>159

4

>129-159

3

>109-129

2

>69-109

0

>49-69

2

≤49

4

Heart rate (beats per minute)

≥180

4

140 to <180

3

110 to <140

2

70 to <110

0

55 to <70

2

40 to <55

3

<40

4

Respiratory rate (breaths per minute)

≥50

4

35 to <50

3

25 to <35

1

12 to <25

0

10 to <12

1

6 to <10

2

<6

4

Oxygenation

FiO₂ ≥ 50%

A-a gradient >499

4

A-a gradient 350-499

3

A-a gradient 200-349

2

A-a gradient <200

0

FiO₂ < 50%

PaO2 >70

0

PaO2 = 61-70

1

PaO2 = 55-60

3

PaO2 <55

4

Laboratory test results

Hematocrit (%)

No. of points

≥60

4

50 to <60

2

46 to <50

1

30 to <46

0

20 to <30

2

<20

4

White blood count (mm³)

≥40 000

4

20 000 to <40 000

2

15 000 to <20 000

1

3 000 to <15 000

0

1 000 to <3 000

2

<1 000

4

Arterial pH

≥7.70

4

7.60 to <7.70

3

7.50 to <7.60

1

7.33 to <7.50

0

7.25 to <7.33

2

7.15 to <7.25

3

<7.15

4

Potassium (mmol/L)

≥7.0

4

6.0 to <7.0

3

5.5 to <6.0

1

3.5 to <5.5

0

3.0 to <3.5

1

2.5 to <3.0

2

<2.5

4

Sodium (mmol/L)

≥180

4

160 to <180

3

155 to <160

2

150 to <155

1

130 to <150

0

120 to <130

2

111 to <120

3

<111

4

Creatinine (mg/100 mL)

Acute renal failure:

≥3.5 + acute renal failure

8

2.0 to <3.5 + acute renal failure

6

1.5 to <2.0 + acute renal failure

4

Chronic renal failure:

≥3.5 + chronic renal failure

4

2.0 to <3.5 + chronic renal failure

3

1.5 to <2.0 + chronic renal failure

2

Chronic/acute:

0.6 to <1.5

0

<0.6

2

🙋 Our APACHE II score calculator can be embedded into your page using our widget, available at the top of the page.

Łucja Zaborowska, MD, PhD candidate
Patient's characteristics
Age
years
History of severe organ insufficiency
No
Renal failure
No
On examination
Temperature
°F
Glasgow Coma Scale
Mean arterial pressure
mmHg
Heart rate
bpm
Respiratory rate
breaths per min
FiO₂
<50%
PaO₂
>70
Lab tests
Hematocrit
%
White blood count
/μL
Arterial pH
Potassium (K⁺)
mmol/L
Sodium (Na⁺)
mmol/L
Creatinine
mg/dL
Result
Apache II score
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