Assessment of individual organ failure
The degree of failure of six main organs can be assessed as follows, although the gastrointestinal tract is an elusive organ to evaluate.
1. Respiratory function is best assessed by the evaluation of gas exchange, most commonly using the Pao2/Fio2 ratio. The need for mechanically assisted ventilation may be taken into account.
2. Renal function: urea (or blood urea nitrogen), and creatinine levels can adequately assess the degree of renal dysfunction. The creatinine clearance may be a more precise measure but is not determined daily in many intensive care units (ICUs). Oliguria is another variable that can be employed.
3. Hematological function: coagulation abnormalities are probably the most important indicator of hematological malfunction and are best measured by the platelet count, the prothrombin time, and the activated partial thromboplastin time. A low hematocrit or an abnormal white cell count may be included.
4. Liver function: the degree of hyperbilirubinemia is the most useful index. Levels of the liver enzymes serum glutamic oxaloacetic transaminase and serum glutamic pyruvic transaminase may give useful additional information. Some groups have suggested the use of prothrombin time, but this may reflect abnormalities of the coagulation system and not just liver dysfunction.
5. Cardiovascular function: no specific indicator is a reliable measure of cardiac function, but the presence of significant hypotension is useful. The degree of adrenergic support may be valuable, even though it is clearly a therapeutic measure.
6. Neurological function: the Glasgow Coma Scale is commonly used to assess neurological dysfunction. A major problem with the assessment of neurological function in the intensive care patient is the frequent use of sedatives and analgesics.
7. Gastrointestinal function: it is widely accepted that it would be useful to assess the degree of gastrointestinal dysfunction, particularly with the current interest in the role of the gut in the pathogenesis of multiple organ failure. However, accurate assessment of gastrointestinal function is still virtually impossible. One of the best indicators that could be used is tolerance to enteral feeding, but there is no single objective method of measuring this, and individual interpretation makes it impractical for use in a scoring system.