Objective, quantitative measurement of severity of illness in critically ill patients

Severity of illness must be quantitated in critically ill patients if studies of outcome and therapeutic efficacy [are to be meaningful. Objective physiologic indicators of critical illness, such as pertinent laboratory values, can be quantitated using the Therapeutic Intervention [Scoring System—TISS. TISS data were obtained for 199, consecutive Class IV critically ill surgical ICU patients and compared to the same data obtained in less critically ill Class II and III ICU patients who served as the control group. For the physiologic indicators of critical illness, a wide range of normal values was established prospectively. The actual values generated by Class IV patients were compared to values of the same indicators as measured in Class II and III ICU patients. Of all objective indicators of critical illness, 55% were either outside the normal range or more than 2 SD away from the mean value of objective indicators for [Class II and III ICU patients; 49% were beyond the normal range or more than 3 SD away. Of all TISS indicators, 73% were abnormal, and 36% of all physiologic indicators were still abnormal despite massive therapeutic support when compared to Class II or III ICU patients. Those patients who had more than 40% of; their physiologic indicators abnormal were more likely to die. However, the percentage of abnormal TISS indicators did not discriminate between patients who died and those who lived, because almost all patients received massive support. These results demonstrate the extremely abnormal physiology and the need for massive support in Class IV critically ill patients when compared to other types of, ICU patients. Because conventional care protocols preclude support systems necessary to maintain life, let alone institute specific therapy required by these critically ill patients, it is unlikely that these Class IV patients would have survived their critical illness in the absence of intensive care facilities and resources.