Age- and weight-based differences in haemodialysis prescription and delivery in children, adolescents and young adults.

Background: Limited systematic data are available on prescription and dosing of haemodialysis (HD) in children and adolescents compared with adults. We aimed to characterize age- and weight-based differences in HD delivery in children, adolescents and young adults.

Methods: This is a retrospective observational study including 1852 patients <30 years on chronic HD from childhood (53 903 HD sessions), receiving thrice weekly outpatient HD between 2004 and 2016 in the USA (6075 patient-years, of which 2535 were in patients aged 1-18 years; weight range 8.3-168 kg). Median individual prescriptions per year were calculated and overall 50% (IQR) and 90% distribution ranges over age and weight were derived. Repeated measurements analysis of variance assessed differences between age and weight groups.

Results: Prescriptions significantly differed among age and weight groups (P < 0.001). Lower weight patients (<75 kg) had higher (inter-quartile range, IQR) weight-normalized blood flow rate (highest in <25 kg: QB/kg = 6.5-9.1 mL/min/kg), urea dialytic clearance (KD/kg) and single pool Kt/V (spKt/V) (<25 kg: 1.43-1.78; 25-50 kg: 1.52-1.92; 50-75 kg: 1.43-1.74) than heavier patients (lowest in >100 kg: QB/kg = 3.1-4.0 mL/min/kg, spKt/V = 1.22-1.47, respectively). Adolescents had significantly lower QB/kg, KD/kg and spKt/V (1.34-1.71) compared with adults (1.45-1.79) and children <12 years (range of 25th percentiles: 1.37-1.44). Dialytic clearance derived from a mechanistic equation underpredicted KD in children but not in young adults. Significant growth retardation was observed, with the proportion of patients <3rd percentile (height for age) decreasing from 71% (1-2 years) to 15% (>18 years).

Conclusion: Delivered HD treatment varies with age and weight and is more intensified in children aged <12 years, compared with adolescents and overweight young adults, who appear to be at highest risk of receiving suboptimal treatment. Still, delivery of target or higher spKt/V values did not result in appropriate growth in these children, questioning the value of spKt/V as a measure of HD adequacy in children. Provided ranges of outpatient HD prescription can help clinicians and researchers in personalizing and optimizing delivery of dialysis treatment.