Multiple organ dysfunction: baseline and serial component scores

Abstract

Objective: The multiple organ dysfunction score (MODS) describes and quantifies organ-specific physiology. The objective of this study was to examine the relation between six components of MODS (cardiovascular, respiratory, renal, central nervous system, hepatic, and hematologic) measured at admission to the intensive care unit (ICU) and during the ICU stay, with time to death in the ICU.

Design: Prospective observational cohort study.

Setting: Sixteen Canadian ICUs.

Patients: A total of 1,200 patients were mechanically ventilated for >48 hrs.

Measurements and main results: The six organ systems comprising MODS were measured at ICU admission (baseline scores) and daily thereafter. The change in organ dysfunction each day (serial scores) were calculated as daily component scores minus the corresponding baseline component scores. In Cox regression analyses, the independent explanatory variables were the MODS components measured at baseline and serially, and the dependent variable was the time from admission to ICU mortality. When each organ system was analyzed individually, both the baseline and serial MODS for the cardiovascular, respiratory, renal, central nervous system, and hematologic components were significantly associated with ICU mortality. After adjusting for the serial hepatic score, the baseline hepatic score was unrelated to mortality. After adjusting for all baseline and serial MODS components in aggregate, four organ systems were significantly associated with ICU mortality: cardiovascular (baseline relative risk [RR], 1.5; serial RR, 1.4); respiratory (baseline RR, 1.4; serial RR, 1.4); renal (baseline RR, 1.3; serial RR, 1.5); and central nervous system (baseline RR, 1.6; serial RR, 1.7). We found that the relative risk of mortality related to organ dysfunction varied significantly over time and among organ systems. Baseline respiratory function was not associated with mortality until the second ICU week (week 1: RR, 1.1 [0.9-1.4]; week 2 onward: RR, 1.9 [1.5-2.4]); the same was true for the change in respiratory function as measured by the serial respiratory score (week 1: RR, 1.2 [1.0-1.5]; week 2 onward: RR, 1.7 [1.4-2.1]). The serial hepatic score was not associated with mortality until the fourth ICU week (weeks 1-3: RR, 0.9 [0.7-1.1]; week 4 onward: RR, 1.4 [1.0-2.0]).

Conclusions: Organ dysfunction scores describe physiology at ICU admission and during ICU stay. Although patterns vary by system, daily MODS component scores provide additional prognostic value over baseline MODS.