title: Serum ionized magnesium in premature and term infants.
abstract: Magnesium is the element with the second highest concentration in the body and is found almost entirely in the intracellular compartment. The small serum component gives a poor representation of the active, physiologic state of the metal. This state is assessed much better by measuring ionized magnesium in the serum, which can now be performed with a sensitive ion-selective electrode. This study was undertaken to establish the normal serum ionized magnesium levels in newborn infants and to define normal serum ionized calcium/ionized magnesium ratios. Ninety-seven infants were investigated. Six were born before 32 weeks gestation, 28 between 33 and 37 weeks gestation, and 63 were term. Ionized magnesium levels were 0.69 +/- 0.14 mmol/L, 0.63 +/- 0.10 mmol/L, and 0.57 +/- 0.07 mmol/L in each group, respectively. These findings demonstrate a significant decline in serum ionized magnesium with increasing maturity. This decrease may relate to a greater need for magnesium uptake during earlier gestation, more magnesium-induced vasodilation to maintain adequate blood flow to developing tissues and organs, or immature parathormone function earlier in pregnancy. The progressive rise in serum ionized calcium/ionized magnesium ratios found herein supports the latter hypothesis.
authors.affiliation: Department of Pediatrics, SUNY-Health Sciences Center, Brooklyn, New York 11203, USA.
authors.forename: J C
authors.initials: JC
authors.lastname: Marcus
authors.forename: G B
authors.initials: GB
authors.lastname: Valencia
authors.forename: B T
authors.initials: BT
authors.lastname: Altura
authors.forename: R Q
authors.initials: RQ
authors.lastname: Cracco
authors.forename: D
authors.initials: D
authors.lastname: Jean-Baptiste
authors.forename: K
authors.initials: K
authors.lastname: Sinha
authors.forename: B M
authors.initials: BM
authors.lastname: Altura
mesh_terms: D001774:Blood Chemical Analysis / Q000295:instrumentation; D002412:Cations / Q000097:blood; D004566:Electrodes; D005260:Female; D006801:Humans; D007231:Infant, Newborn / Q000097:blood*; D007234:Infant, Premature / Q000097:blood*; D008274:Magnesium / Q000097:blood*; D008297:Male; D012680:Sensitivity and Specificity; D014664:Vasodilation
chemical_list: D002412:Cations; D008274:Magnesium