Daily assessment of organ dysfunction and survival in intensive care unit cardiac surgical patients.

BACKGROUND: The purpose of this study was to develop a specific postoperative score for intensive care unit (ICU) cardiac surgical patients for assessment of organ dysfunction and survival.
METHODS: This prospective study consisted of all consecutive adult patients admitted after cardiac surgery to our ICU over a period of 3 years. Evaluation of variables was performed using the first year patients who stayed in the ICU for at least 24 hours. The reproducibility was then tested in two validation sets using all patients. Performance was assessed with the Hosmer-Lemeshow (chi2 statistics) goodness-of-fit test and receiver operating characteristic (ROC) curves and compared with the Acute Physiology and Chronic Health Evaluation (APACHE II) and Multiple Organ Dysfunction Score (MODS).
RESULTS: A total of 3,230 patients were admitted to the ICU after cardiac surgery. Mean chi2 values for the new score were 5.8 (APACHE II, 11.3; MODS, 9.7) for the construction set, 7.2 (APACHE II, 8.0; MODS, 4.5) for the validation set I, and 5.9 for the validation set II. The mean area under the ROC curve was 0.91 (APACHE II, 0.86; MODS, 0.84) for the new score in the construction set, 0.88 (APACHE II, 0.84; MODS, 0.84) in the validation set I, and 0.92 in the validation set II.
CONCLUSIONS: Our new 10-variable risk index performs very well, with calibration and discrimination very high, better than general severity systems; and it is an appropriate tool for daily risk stratification in ICU cardiac surgery patients. Thus, it may serve as an "expert system" for diagnosing organ failure, decision making, resource evaluation, and predicting mortality among ICU cardiac surgical patients.