Tamara van Donge

Dynamics of creatinine in ELBW neonates 131 7 Table 1: Demographic data presented as median [interquartile range] or as n (%), obs, observations. * defined as maternal betamethasone treatment before birth. Characteristics Model building dataset Evaluation dataset ELBW neonates 148 (2814) 69 (1212) obs. per patient 20 [14, 25] 18 [13, 22] Gestational age (weeks) 27 [25, 28] 27 [26, 28] Birth weight (g) 820 [710, 900] 840 [735, 910] Current weight (g) 920 [795, 1105] 924 [786, 1171] obs. per patient 5 [3, 6] 5 [4, 6] Ibuprofen treatment (yes) 96 (64%) 37 (54%) Inotropes treatment (yes) 76 (51%) 23 (34%) Mode of delivery Vaginal 51 (34%) 19 (28 %) Cesarean 97 (65%) 50 (72 %) Sex Female 85 (57%) 30 (44%) Male 63 (42%) 39 (56%) Lung maturation* 128 (86%) 56 (81%) Neonatal death 18 (12%) 10 (14.5%) Crea conc 1 st day of life (mg/dl) 0.57 [0.5, 0.68] 0.71 [0.59, 0.83] Model development Data was described by a turn-over model, assuming a constant creatinine production and time-varying (i.e. postnatal age-dependent) net creatinine clearance (baseline clearance (CL BL ) + postnatal age-dependent clearance increase due to postulated decrease in reabsorption). Hence, if the produced creatinine amount per time interval is greater than the eliminated amount, an increase in Scr will be observed (and vice versa); steady-state Scr will be achieved if the produced creatinine amount equals the eliminated amount. (0) = !"#$% Equation 2 = !"#$%&'(#) − ( ) *+(,()-'(#) × ( ) Equation 3 ( ) !"#$#%&'#(% = ( ) = )* + . × +#"" ,- +#"" + +#"" 4 0.7 . */0 1 × ℎ (/0) Equation 4