External validation cohort
For the external validation of the developed models, data from 53,943 patient-days from 9576 patients were used, corresponding to 45.8% of the University Hospitals Leuven patients included in the M@tric database. Compared to the development cohort, the age was younger (median (IQR) 65.6 (54.6–75) years, p < 0.01), emergency admission was less frequently (n = 3231, 33.7%, p < 0.01), APACHE II score was lower (median (IQR) 17 (13–21), p < 0.01), cardiac surgery was still the major admission diagnosis but occurred less often (n = 3229, 33.7%, p < 0.01), and average CrCl over the entire ICU stay was similar (median (IQR) 93.1 (56.2–133.6) ml/min, p = 0.7) (Table 