The MPM II (Mortality Prediction Model) is based on 12,610 patients from multiple hospitals and was developed in 1993. The MPM score is measured immediately on admission (MPM0). It can be refined after 24 hours (MPM24) by updating five of the admission variables and by including eight additional variables such as arterial blood gases, creatinine, prothrombin time, urine output, etc. Each of these variables is entered into a complex mathematical formula whose solution provides the predicted mortality.