MORTALITY PROBABILITY-MODELS FOR PATIENTS IN THE INTENSIVE-CARE UNIT FOR 48 OR 72 HOURS - A PROSPECTIVE, MULTICENTER STUDY

Objective: To develop models in the Mortality Probability Model (MPM I I) system to estimate the probability of hospital mortality at 48 and 72 hrs in the intensive care unit (ICU), and to test whether the 24-hr Mortality Probability Model (MPM(24)), developed for use at 24 hrs in the ICU, can be used on a daily basis beyond 24 hrs. Design: A prospe ctive, multicenter study to develop and validate models, using a cohor t of consecutive admissions. Setting: Six adult medical and surgical I CUs in Massachusetts and New York adjusted to reflect 137 ICUs in 12 c ountries. Patients: Consecutive admissions (n = 6,290) to the Massachu setts/New York ICUs were studied. Of these patients, 3,023 and 2,233 p atients remained in the ICU and had complete data at 48 and 72 hrs, re spectively. Patients <18 yrs of age, burn patients, coronary care pati ents, and cardiac surgical patients were excluded. Outcome Measure: Vi tal status at the time of hospital discharge. Results: The models cons ist of five variables measured at the time of ICU admission and eight variables ascertained at 24-hr intervals. The 24-hr model demonstrated poor calibration and discrimination at 48 and 72 hrs. The newly devel oped 48- and 72-hr models-MPM(48) and MPM(72)-contain the same 13 vari ables and coefficients as the MPM(24). The models differ only in their constant terms, which increase in a manner that reflects the increasi ng probability of mortality with increasing length of stay in the ICU. These constant terms were adjusted by a factor determined from the re lationship between the data from the six Massachusetts and New York IC Us and a more extensive data set, from which the ICU admission Mortali ty Probability Model (MPM(0)) and MPM(24) were developed. This latter data set was assembled from ICUs in 12 countries. The MPM(48) and MPM( 72) calibrated and discriminated well, based on goodness-of-fit tests and area under the receiver operating characteristic curve. Conclusion s: Models developed for use among ICU patients at one time period are not transferable without modification to other time periods. The MPM(4 8) and MPM(72) calibrated well to their respective time periods, and t hey are intended for use at specific points in time. The increasing co nstant terms and associated increase in the probability of hospital mo rtality exemplify a common clinical adage that if a patient's clinical profile stays the same, he or she is actually getting worse.