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APACHE (AcutePhysiologyAndChronicHealthEvaluation)
There are various ways of qualitative control of health services. One, which is particularly popular, is counting the frequency of undesirable events. Mortality is often used in categorizing the outcome in patients suffering from acute and life threatening conditions. However in the group of patients that died as well as in the group of patients that survived, some patients may have lived after having received poor quality care while others may have died having received excellent quality care.
One way of measuring quality of care provided by health services is to
check in a group of patients the mortality factors and see if these are
higher or lower than those expected taking in account the severity of
their illness. In order for this to happen it is important to be able
to separate the effects of illness severity from the effects of 0quality
of care provided.
Two methods are available:
- To randomly distribute patients into different therapeutic institutions that all have the same possibility of admitting patients with severe or less severe conditions.
- To measure the severity of each case and then to statistically explain the fluctuation of the mortality factors initially in all levels of disease severity and then to relate these fluctuations to quality of care.
Because the first method of randomly distributing patients in different
therapeutic institutions is rather difficult, the second approach is more
common and is known as
‘severity adjusted assessment of outcomes’.
The APACHE II scale gives a mathematical estimation of the severity of the patient’s condition. With a further calculation it also provides us with the probability that each patient has to die from the specific problem at the specific time.
The areas included are:
- Age
- Past history of severe organ failure or immunodeficiency
- Rectal temperature
- Mean arterial pressure
- Heart rate
- Respiratory rate
- Blood oxygen(value taken by measuring the PO2 with a blood gas analyzer
- PH of blood
- Serum Na
- Serum K
- Creatinine
- Hematoctrit
- Number of white cells
- 15-GCS (Glasgow coma scale rating)
From the above parameters we obtain the score of the APACHE II scale.
Then a list of 50 disease categories follows. To each one there is a corresponding cofactor-usually a negative number.
R is the death risk of the specific patient. The following formula calculates the neperian logarithm of (R/1-R), i.e. (R/1-R):
In (R/I-R) =-3.517+ (APACHE scorex0.146) + (0.603 only if the patient
has been subjected to an emergency operative procedure) + (the cofactor
of the disease category).
If this logarithm is labeled x, then the risk R is equal to:
R = e (to the x)/1-e (To the x).
All this of course does not need to be done manually. There are programs
to do this. Soon the ‘FORMULAE’ section of our pages will be available
on line being a tool to estimate the APACHE II score.
Disadvantages
- The APACHE II score has been designed for patients in intensive care
units (ICU).
There are no studies available which correlate measurable risks with real mortality of ICU patients. - Sometimes it is not able to measure the risk at all e.g. in the patient with severe cerebral injury and is kept alive with mechanical means, the APACHE II score will estimate probability of mortality of 30-40%, whereas the real probability is 100%.
Despite these problems the score continues to be a good index of patient severity. When estimated during the patient’s admission, it provides a rating which shows if the patient is improving or deteriorating. The APACHE II score, in the absence of a better measuring tool, is used by 1051 for the valuating the adequacy of the home care it provides.