Abstract
Acute neonatal hyperammonemia is associated with poor neurological outcomes and high mortality. We developed, based on kinetic modeling, a user-friendly and widely applicable algorithm to tailor the treatment of acute neonatal hyperammonemia. A single compartmental model was calibrated assuming a distribution volume equal to the patient’s total body water (V), as calculated using Wells’ formula, and dialyzer clearance as derived from the measured ammonia time–concentration curves during 11 dialysis sessions in four patients (3.2 ± 0.4 kg). Based on these kinetic simulations, dialysis protocols could be derived for clinical use with different body weights, start concentrations, dialysis machines/dialyzers and dialysis settings (e.g., blood flow QB). By a single measurement of ammonia concentration at the dialyzer inlet and outlet, dialyzer clearance (K) can be calculated as K = QB∙[(Cinlet − Coutlet)/Cinlet]. The time (T) needed to decrease the ammonia concentration from a predialysis start concentration Cstart to a desired target concentration Ctarget is then equal to T = (−V/K)∙LN(Ctarget/Cstart). By implementing these formulae in a simple spreadsheet, medical staff can draw an institution-specific flowchart for patient-tailored treatment of hyperammonemia.
Highlights
Introduction published maps and institutional affilAcute hyperammonemia is a rare but life-threatening condition in the neonatal period, most commonly caused by inborn errors of metabolism (IEM) such as urea cycle disorders [1,2] and organic acidemias [3,4]
Two neonates were already initiated on nitrogen-scavenging agents in the referring hospital (1 h 23 to 13 h 05 prior to hemodialysis initiation), while the other two patients were started on adequate nutritional and medical management including nitrogen-scavenging agents upon their arrival at our center
HD sessions in total for which sufficient data were available for the kinetic analysis: i.e., five with the 4008 dialysis machine with FXPaed dialyzer, and six with the CarpeDiemTM
Summary
Introduction published maps and institutional affilAcute hyperammonemia is a rare but life-threatening condition in the neonatal period, most commonly caused by inborn errors of metabolism (IEM) such as urea cycle disorders [1,2] and organic acidemias [3,4]. A partial or complete inactivity of enzymes responsible for eliminating nitrogenous waste products results in acute hyperammonemic episodes [1,2,5,6]. During these events, ammonia diffuses into the brain where it exerts severe brain toxicity, resulting in severe neurological sequelae or even death [1,5,6,7]. Brain toxicity and neurological outcome is strongly related to the duration and severity of the hyperammonemia. Early diagnosis and adequate management of hyperammonemia are considered key to improving the neurological outcome of affected neonates [1,10,11,12,13,14,15]
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