APACHE II Score

Why Use

Mortality prediction scores such as APACHE II are often used to assess the baseline risk groups being compared in clinical trials. They can also be used to determine prognosis and help family members make informed decisions about the aggressiveness of care.

When to Use

This score can be calculated on all patients newly admitted to the intensive care unit. While it is not mandatory and will not help with patient management, it is a useful tool for risk stratification and to compare the care received by patients with similar risk characteristics in different units.

Formula

Pearls / Pitfalls

APACHE II is the most widely used ICU mortality prediction score. It differs from the original APACHE score in some ways; the number of variables is decreased and the weight of some of the variables is adjusted. APACHE III and APACHE IV scores were also developed but are not commonly used because their statistical method is under copyright control. The score was derived in a general ICU population and may be less precise when applied to specific populations such as liver failure or HIV patients. Since APACHE II was studied on patients newly admitted to the ICU, it is not accurate when dealing with patients transferred from another unit or another hospital. This is known as lead time bias and is addressed in APACHE III. The APACHE II score must be recalibrated before it can be used in a population other than the one it was derived in. ICU prediction scores in general need to be periodically recalibrated to reflect changes in practice and patient demographics.

Management

The APACHE II score was designed as a mortality prediction tool but was not intended to influence the medical management of patients during their ICU stay.

Critical Actions

A number of variables are used to calculate the APACHE II score. The worst values recorded during the initial 24 hours in the ICU should be used. Alternatively, the variables initially recorded during the patient’s admission can be used for practical reasons. The APACHE II score is calculated at the beginning of the ICU admission to help determine the patient’s mortality risk for the admission. It is not calculated sequentially and is not meant to show improvement or effect of interventions. As such it should not be used to direct medical management.

More Information

The APACHE-II Score provides an estimate of ICU mortality based on a number of laboratory values and patient signs taking both acute and chronic disease into account. Note : The data used should be from the initial 24 hours in the ICU, and the worst value (further from baseline/normal) should be used. The following defines “chronic organ insufficiency” and immunocompromise: Liver insufficiency Biopsy proven cirrhosis Documented portal hypertension Episodes of past upper GI bleeding attributed to portal hypertension Prior episodes of hepatic Cardiovascular New York Heart Association Class IV Heart Failure Respiratory Chronic restrictive, or vascular disease resulting in severe exercice restriction, i.e. unable to climb stairs or perform household duties Documented chronic hypoxia, hypercapnia, secondary severe pulmonary hypertension (>40 mmHg), or respirator dependency Renal Receiving chronic dialysis Immunosuppression The patient has received therapy that suppresses resistance to infection e.g. immuno-suppression, chemotherapy, radiation, or recent hight dose steroids, or has a disease that is sufficiently advanced to suppress resistance to infection, e.g. leukemia, lymphoma, AIDS Point values Criteria Point values Age, years ≤44 0 45-54 +2 55-64 +3 65-74 +5 >74 +6 History of severe organ insufficiency or immunocompromised Yes, and nonoperative or emergency postoperative patient +5 Yes, and elective postoperative patient +2 No 0 Rectal temperature, °C ≥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 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 (use PaO2 if FiO2 <50%, otherwise use A-a gradient ) A-a gradient >499 +4 A-a gradient 350-499 +3 A-a gradient 200-349 +2 A-a gradient <200 (if FiO2 over 49%) or pO2 >70 (if FiO2 less than 50%) 0 PaO 2 = 61-70 +1 PaO 2 = 55-60 +3 PaO 2 <55 +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 Serum 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 Serum 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 Serum creatinine, mg/100 mL ≥3.5 and ACUTE renal failure* +8 2.0 to <3.5 and ACUTE renal failure +6 ≥3.5 and CHRONIC renal failure +4 1.5 to <2.0 and ACUTE renal failure +4 2.0 to <3.5 and CHRONIC renal failure +3 1.5 to <2.0 and CHRONIC renal failure +2 0.6 to <1.5 0 <0.6 +2 Hematocrit, % ≥60 +4 50 to <60 +2 46 to <50 +1 30 to <46 0 20 to <30 +2 <20 +4 White blood count, total/cubic mm in ≥40 +4 20 to <40 +2 15 to <20 +1 3 to <15 0 1 to <3 +2 <1 +4 Glasgow Coma Scale (GCS) 1 - 15 15 - [GCS Score] *Note: "acute renal failure" was not defined in the original study. Use clinical judgment to determine whether has acute kidney injury. Cutoffs differ slightly from original study (by less than 0.1 mg/dL) in order to account for all possible values in this electronic calculator. Approximated in-hospital mortality rates APACHE II Score Nonoperative Postoperative 0-4 4% 1% 5-9 8% 3% 10-14 15% 7% 15-19 25% 12% 20-24 40% 30% 25-29 55% 35% 30-34 73% 73% >34 85% 88% From Knaus et al. 1985 .