Predicting Outcome in  Critical Care?

Outcome prediction models and severity of illness scoring systems use chronic health information and age as indicators of physiologic reserve.

They also use markers of organ dysfunction to quantify how sick the patient is.

The combined score has been used as a method of predicting outcome, but the results are not 100% reliable.

The prediction of outcomes in intensive care is something of an industry, and numerous scoring systems have been developed to assist the physician with predicting mortality and/or severity of illness (Apache I, II & III, SAPS, MPM, MOF score and SOFA). Although none of these systems is perfect at predicting mortality, there is overall a strong relationship between the patient’s age and chronic health statutes, acute physiologic upset, sequential organ failure and death.

These systems, such as the popular Apache models, use chronic health information and age as indicators of physiologic reserve. By chronic health information I mean evidence of liver, heart, respiratory or renal disease. A patient on home oxygen for COPD or who has dyspnea from heart failure on minimal exertion has minimal baseline reserve. In addition, as we have seen, advancing age is associated with organ deterioration. The models then look at acute physiologic upset – respiratory dysfunction, shock, renal failure, electrolyte abnormalities etc to quantify how acutely sick the patient is. The combined number has been used for outcome prediction.

For example, the Multi Organ Dysfunction Score (Marshall 1995), has been proposed as a method of predicting outcomes in intensive care. The method of calculating this is recorded in the table below and the relationship between score and mortality is graphically represented alongside. As you can see, there is an almost linear relationship between extent of organ dysfunction and mortality. Organ preservation thus is a fundamental objective of critical care. We will explore this further in the tutorial on scoring systems.

There is no ideal method of predicting outcome, but when resources are scarce it is important to prioritize patients in order of potential benefit from ICU admission. One must ask: what can we do for this patient? What intensive care interventions are necessary? What is the possibility of this patient surviving? It is important that intensive care units are not filled with patients who would do just as well elsewhere. On the other hand it is essential that admission is not delayed until such a time as the patient is no longer salvageable.

Please note: these tutorials are for personal study purposes only.  They are not currently peer reviewed, and no responsibility will be taken for mistakes or inaccuracies. Reproduction of information is forbidden. All material is copyrighted by the GasWorks Group.