title: A pitfall of measuring lithium levels in neonates.
abstract: If lithium therapy is required during pregnancy or lactation, serum lithium monitoring may be indicated in the newborns. In the neonatal population, however, blood samples are often obtained with a sampling device containing lithium heparin. Given the infrequent nature of lithium measurement in the neonatal population, a risk of oversight on the use of these lithium-containing devices for lithium measurements exists. Two such neonatal cases are reported, which may have been mismanaged if the measured levels of lithium were not suspected to be spurious. Patient 1 was a 3-day-old infant with a congenital heart disease born at 31 weeks' gestation to a mother on lithium. After a surgical repair, because of a potential need to monitor lithium in the infant's serum during breastfeeding, a remaining sample of apparently serum from a previous blood testing on day 1 of life was measured for lithium as a baseline value. Despite the lack of toxic signs, the result showed a toxic lithium level of 4.19 mmol/L. Lithium levels in follow-up samples were 0.11 mmol/L (day 4) and undetectable (day 6). Patient 2 was a full-term infant exposed to maternal lithium throughout the fetal life and breastfeeding. Serum lithium at day three of life in a hospital was undetectable, but after discharge, the lithium concentrations increased to 1.1 mmol/L on day 18, with no sign of lithium toxicity or renal dysfunction. This raised a possibility of significant exposure through breastfeeding, but later they were found to be spurious due to the use of lithium-containing devices. Separate investigation of effects of sampling devices on lithium levels indicated that levels of >3 mmol/L were possible if a sampling volume of blood was substantially small compared with the capacity of a tube containing lithium heparin [corrected]
authors.affiliation: Motherisk Program, Division of Clinical Pharmacology and Toxicology, Department of Paediatrics, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Tanaka
authors.forename: Myla E
authors.initials: ME
authors.lastname: Moretti
authors.forename: Zulfikarali H
authors.initials: ZH
authors.lastname: Verjee
authors.forename: Michael
authors.initials: M
authors.lastname: Shupak
authors.forename: Katalin E
authors.initials: KE
authors.lastname: Ivanyi
authors.forename: Shinya
authors.initials: S
authors.lastname: Ito
mesh_terms: D000328:Adult; D001714:Bipolar Disorder / Q000188:drug therapy; D001800:Blood Specimen Collection / Q000295:instrumentation; D003951:Diagnostic Errors / Q000517:prevention & control*; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D018020:Lithium Compounds / Q000097:blood* / Q000627:therapeutic use; D008297:Male
chemical_list: D018020:Lithium Compounds