Background: The Injury Severity Score (ISS) has been observed consistently to be a robust predictor of postinjury multiple organ failure (MOF). However, the ISS fails to account for multiple injuries to the same body region. Recently, the “new” ISS (NISS) has been proposed to address this shortcoming. Preliminary studies suggest the NISS is superior to the ISS in predicting trauma mortality. Our purpose was to determine whether the NISS is a better predictor of postinjury MOF than the ISS.
Methods: A total of 558 patients admitted to our Level I trauma center with ISS > 15, age > 15 years, and survival > 48 hours were prospectively identified; 101 (18%) developed postinjury MOF. Data characterizing postinjury MOF were collected, and the NISS was calculated retrospectively. The ISS and NISS were compared as univariate predictors of MOF. Multivariate analysis was used to determine whether substitution of NISS for ISS resulted in a superior predictive model.
Results: In 295 patients (53%), the NISS was greater than the ISS. This subgroup of patients experienced a greater frequency of MOF (26.7% vs. 8.3%, p < 0.0001), a higher mortality (12.8% vs. 4.9%, p < 0.001), and a higher early transfusion requirement (6.7 U vs. 3.6 U, p < 0.0001) compared with the group in which NISS equaled ISS. Moreover, the NISS yielded better separation between patients with and without MOF reflected by the greater difference in median NISS scores compared with ISS scores. The multivariate predictive model, including NISS, showed a better goodness of fit compared with the same model that included ISS.
Conclusions: The NISS is superior to the ISS in the prediction of postinjury MOF. This measure of tissue injury severity should replace the ISS in trauma research.
Extensive investigative efforts have advanced our understanding of the pathophysiology of postinjury multiple organ failure (MOF). 1–8 Unfortunately, this advancement has not translated into improved outcome. 9 Clinical trials of newer therapeutic modalities aimed at modulating the inflammatory response have been disappointing. 10–14 This failure is largely related to the complexity of the inflammatory response;1,5,6,15,16 but the early identification of high-risk patients has been problematic as well. 2
Measures of tissue injury, in particular the Injury Severity Score (ISS), have consistently emerged as robust predictors of postinjury MOF. 18–22 However, the ISS has been plagued by several inadequacies. 23 In particular, it fails to account for multiple injuries to the same body region, limiting its usefulness in penetrating trauma. 24 The Anatomic Profile (AP) 25,26 and a Severity Characterization of Trauma (ASCOT) 27 were introduced to address these shortcomings; however, they offered only modest gains in predicting trauma mortality. 28,29 Moreover, their computational complexity further hindered general acceptance as an alternative to the ISS. 29 Recently, Osler et al. 30 reported a new ISS (NISS) based on the three most severe injuries, regardless of body region. This simple modification of the ISS was demonstrated to improve mortality prediction, especially after penetrating trauma. The purpose of this study was to determine whether the NISS is also a superior predictor of postinjury MOF compared with the ISS.