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Plenary Lecture

Creatinaemia in neonates: from biochemical quantification to clinical interpretation

Dr. Karel Allegaert
Neonatal Intensive Care Unit
University Hospitals Leuven
BELGIUM
E-mail: karel.allegaert@uzleuven.be

Abstract: Recognition of acute renal failure (ARF) in neonates is of relevance to adapt medical treatment and as prognostic indicator during neonatal stay. The incidence of ARF in neonates however is extremely variable due to the absence of a robust definition of renal impairment in neonates and due to the use of fixed cut off values for serum creatinine (Scr) despite maturational differences within the preterm age. We therefore aimed to describe postnatal Scr trends and its covariates in a cohort of extreme low birth weight (ELBW, i.e. < 1000 g) infants.
Serum creatinine (Scr) reflects to a certain extent glomerular filtration rate in neonates, but also depends on the technique used to quantify Scr [Jaffe colorimetry or enzymatic quantification].We compared observations of maternal-neonatal ELBW samples in whom Jaffe or compensated Jaffe (maternal) and enzymatic quantification (neonate) were applied. Finally, in an attempt to quantify differences between these techniques, we compared postnatal Scr trends in two consecutive cohorts of extremely low birth weight (ELBW) neonates before and following a switch from Jaffe to enzymatic Scr quantification. Postnatal Scr (day 1,2,3,4,5,6,7,14,21,28,42) in a cohort of 151 ELBW neonates (Jaffe) was compared to 116 more recently admitted ELBW neonates (enzymatic).
Firstly, ELBW neonates display trends similar to heavier neonates, but peak Scr is higher, the subsequent decrease slower. Raised creatinemia in ELBW neonates reflects both immaturity (the lower GA, the higher the peak Screa and the slower the subsequent decrease) and morbidity (ventilation, Apgar, ibuprofen). Secondly, the quantification method affect the paradigm that creatinaemia at birth is similar to maternal creatinaemia. Creatinaemia values in mothers and neonates depend on the method used. Method-specific reference values are needed. Finally, while clinical characteristics were similar, median postnatal Jaffe Scr (66,88,96,95,86,82,77,68,60,54 and 49 mmol.l-1) remained significantly higher compared to enzymatic quantification (51,64,80,77,72,70,65,49,39,36 and 31 mmol.l-1, all at least p<0.001) throughout postnatal life (day 1,2,3,4,5,6,7,14,21,28,42). The difference in within-day median values fluctuated between 11-24 mmol.l-1. It was therefore concluded that there is no fixed absolute difference between both techniques. A similar comparison between Jaffe and enzymatic quantification (pre)term neonates with a birth weight above 1 000 g confirms these findings.
Consequently, clinicians and researchers should use the appropriated age-dependent references values, dependent on the quantification technique used and Scr centiles (dependent on gestational and postnatal age) should be used to evaluate individual observations.

Brief Biography of the Speaker: Karel Allegaert, MD, PhD graduated from the Katholieke Universiteit Leuven as medical doctor (1994), with a subsequent training in Pediatrics/Neonatology (2001) and Clinical Pharmacology (2005). Following the presentation of his PhD defence (neonatal analgesia: towards an integrated approach), he further combined clinical care as a consultant of the neonatal intensive care unit, University Hospitals Leuven with clinical research with specific emphasis on perinatal clinical pharmacology (special populations, including preterm neonates and pregnancy). He was appointed as associated professor of the Katholieke Universiteit Leuven in 2005, and subsequently further developed these research activities, currently reflected in about 200 publications in national and international journals, conference proceedings and chapters in book. His clinical research has (FWO clinical doctoral grant) and still is supported by a Fundamental Clinical Investigatorship (2009-2013) of the FWO Vlaanderen. This research also resulted in several awards of the Belgian Academy of Medicine and Sciences (Govaerts award for Clinical Toxicology 2006-2008, and Heymans Award Clinical Pharmacology 2002-2004), the Belgian Pain Society (2005),and the Galenus price, clinical research pharmacology, Belgium (2009).