Predicts hospital mortality in ICU based on physiological patient data and chronic health conditions.
In the text below the calculator there is more information about the scoring method, its variables and about the score interpretation.
APACHE II scoring method explained
The Acute Physiology and Chronic Health Evaluation II (APACHE II) is one of the ICU scoring systems that classify disease outcome in hospitalized patients.
The above calculator consists of two different versions of the APACHE II model to answer to specialist preferences.
The first tab from the APACHE II score calculator requires the direct input of clinical data whilst the second tab allows the selection of the intervals in which the patient belongs. The second tab has the advantage of showing the number of points each interval is awarded.
The variables used in both calculation methods are:
■ Chronic health conditions and/ or severe organ system insufficiency or is immunocompromised and the following conditions:
1) Cirrhosis of the liver – biopsy confirmed or portal hypertension or previous history of hepatic failure/encephalopathy/coma.
2) New York Heart Association Class IV cardiovascular disease.
3) Severe COPD -- Hypercapnia, home O2 use, or pulmonary hypertension, documented chronic hypoxia or respiratory dependency.
4) Renal dialysis.
5) Immunocompromised – through immunosuppression therapy, chemotherapy, radiation, long term steroid medication or autoimmune disease such as lymphoma, AIDS.
■ Age – as mortality risk factor in many comorbidities;
■ Temperature in Fahrenheit or Celsius – body temperature as indicator of infection and general health;
■ pH – is factored in as sign of pulmonary, metabolic acidosis and several other conditions;
■ Mean arterial pressure - measured in mmHg, offers information on blood circulation and possible dysfunctions;
■ Heart rate in beats per minute – the predictive value of resting heart rate;
■ Respiratory rate in breaths per minute – respiration rhythm provides information on the respiratory system;
■ Sodium in mEq/L and Potassium in mEq/L – are determined in order to check the serum balance between Na and K;
■ Acute renal failure (ARF) – is used as risk factor for adverse outcome in critically ill patients with aggravated renal condition;
■ Creatinine in mg/dL – provides information about renal function, glomerular filtration rate and muscular activity;
■ Hematocrit % - evaluates the proportion of red blood cells in the blood sample;
■ White blood cell count in x103/µL – factors in a possible infectious state;
■ A - a gradient if FiO2 ≥0.5 or PaO2 if FiO2 <0.5 – offers information on respiratory function;
■ Glasgow coma scale points – the score obtained here is subtracted from the maximum score (15).
The main limitation of the model is the fact that it can only be used in adults, as it has not been validated in pediatric populations.
The table below introduces the variables used and the number of points awarded to each of their intervals.
| Pts | Chronic organ insufficiency | Age | Temp (°C) | pH | Mean arterial pressure in mmHg | Heart rate in beats per minute |
| 4 | - | - | ≥41 | ≥7.7 | ≥160 | ≥180 |
| 3 | - | - | 39 - 40.9 | 7.6 - 7.69 | 130 - 159 | 140 - 179 |
| 2 | - | - | - | - | 110 - 129 | 110 - 139 |
| 1 | - | - | 38.5 - 38.9 | 7.5 - 7.59 | - | - |
| 0 | no | ≤44 | 36 - 38.4 | 7.33 - 7.49 | 70 - 109 | 70 - 109 |
| 1 | - | - | 34 - 35.9 | - | - | - |
| 2 | yes + elective surgery | 45 - 54 | 32 - 33.9 | 7.25 - 7.32 | 50 - 69 | 55 - 69 |
| 3 | - | 55 - 64 | 30 - 31.9 | 7.15 - 7.24 | 40 - 54 | |
| 4 | - | - | ≤29.9 | <7.15 | ≤49 | ≤39 |
| 5 | yes with or without surgery | 65 - 74 | - | - | - | - |
| 6 | - | ≥75 | - | - | - | - |
| Pts | Na in mEq/L | K in mEq/L | Creatinine in mg/dL | Hematocrit % | White blood cell count in x103/µL | A - a gradient if FiO2 ≥0.5 or PaO2 if FiO2 <0.5 |
| 4 | ≥180 | ≥7 | ≥3.5 | ≥60 | ≥40 | ≥500 |
| 3 | 160 - 179 | 6 - 6.9 | 2 - 3.4 | - | - | 350 - 499 |
| 2 | 155 - 159 | - | 1.5 - 1.9 | 50 - 59.9 | 20 - 39.9 | 200 - 349 |
| 1 | 150 - 154 | 5.5 - 5.9 | - | 46 - 49.9 | 15 - 19.9 | - |
| 0 | 130 - 149 | 3.5 - 5.4 | 0.6 - 1.4 | 30 - 45.9 | 3 - 14.9 | <200, >70 PaO2 |
| 1 | - | 3 - 3.4 | - | - | 61 – 70 PaO2 | |
| 2 | 120 - 129 | 2.5 - 2.9 | <0.6 | 20 - 29.9 | 1 - 2.9 | - |
| 3 | 111 - 119 | - | - | - | - | 55 - 60 PaO2 |
| 4 | ≤110 | <2.5 | 1.5 - 1.9 (yes ARF) | <20 | <1 | 2 |
| 5 | - | - | - | - | - | - |
| 6 | - | - | 2 - 3.4 (yes ARF) | - | - | |
Score interpretation
The APACHE II is calculated by a medical professional within 24h of admission and provides an integer score that establishes patient prognosis and mortality risk.
The score ranges from 0 to 71, the higher the score, the higher the severity of the patient’s condition.
A direct connection between increases in score and increases in mortality risk has been found in both surgical and non-surgical patients.
The following table assigns the mortality risk percentages to each APACHE II score interval:
| APACHE II | non op | post op |
| 0 - 4 | 4% | 1% |
| 5 - 9 | 8% | 3% |
| 10 - 14 | 15% | 7% |
| 15 - 19 | 24% | 12% |
| 20 - 24 | 40% | 30% |
| 25 - 29 | 55% | 35% |
| 30 - 34 | 73% | 73% |
| ≥ 35 | 85% | 88% |
About the study
APACHE II was created in 1985 by Knaus et al. following a study on 5815 patients from 13 hospitals.
12 routine physiological measurements have been taken into account, along with patient age, and previous health status. The score has shown good prognostic value in acutely ill patients.
Higher scores have been found closely correlated with the subsequent risk of hospital death in many common diseases.
The model was subsequently validated in a cohort of 1721 patients with the area under the ROC curve found to be higher than 0.8.
Other patient severity score
APACHE II belongs to a group of general illness scoring systems which are used to evaluate the severity, organ dysfunction and prognosis of patients in the ICU and other units.
The most commonly used outcome score is the Glasgow Coma Scale (GCS). The Mortality Probability Model (MPM) predicts hospital mortality while the Multiple Organ Dysfunction Score (MODS) allows an individual organ failure prognostic.
Similar to APACHE II, the Simplified Acute Physiology Score (SAPS) provides information on morbidity and mortality, however, with slightly more factors taken into account.
Original source
Knaus WA, Draper EA, Wagner DP, Zimmerman JE. APACHE II: a severity of disease classification system. Crit Care Med. 1985;13(10):818-29.
Validation
Headley J, Theriault R, Smith TL. Independent validation of APACHE II severity of illness score for predicting mortality in patients with breast cancer admitted to the intensive care unit. Cancer. 1992; 70(2):497-503.
Other references
1. Naved SA, Siddiqui S, Khan FH. APACHE-II score correlation with mortality and length of stay in an intensive care unit. J Coll Physicians Surg Pak. 2011; 21(1):4-8.
2. Niskanen M, Kari A, Nikki P, Iisalo E, Kaukinen L, Rauhala V, Saarela E, Halinen M. Acute physiology and chronic health evaluation (APACHE II) and Glasgow coma scores as predictors of outcome from intensive care after cardiac arrest. Crit Care Med. 1991; 19(12):1465-73.
