Dosing and Pediatrics

 

Dose in Infants

Should the dose of gadolinium be reduced in infants and children?  
gadolinium in infants
 
The dose of gadolinium contrast for infants and children should be the same as that given to adults on a per kilogram basis. This recommendation takes into account two competing factors determining the effectiveness of contrast administration: biological half-life and volume of distribution.
Since newborns and young infants have significantly lower glomerular filtration and renal clearance rates than do older children and adults, the biologic half-life of gadolinium-based MR contrast agents is prolonged. In a full-term newborn the half-life is 6.5 hours; it may be longer than 9 hours in premature infants. By two months of age, the infant half-life reaches the adult value of 1.5 hours.
This prolonged half-life in newborns and young infants results in persisting enhancement of normal structures for up to several hours following injection.  The prolonged half-life thus provides an increased window of time for performing imaging in these patients. For example, a sedated infant who awakes during contrast infusion may be removed from the imager, re-sedated, and re-imaged within 1-2 hours without the need for injection of additional gadolinium.  Alternatively, if only a postcontrast study is desired, the infant may be sedated and given the contrast infusion while still in the neonatal care unit, and then may undergo nonurgent MR imaging. 
gadolinium in infants
Persistent contrast enhancement in a premature neonate seen at 1, 2, 3, and 4 hours after injection. The prolonged half-life (4-9 hrs) of Gd in neonates and young infants provides an expanded postcontrast imaging window.
Renal excretion rates aside, neonates have twice the volume of extracellular fluid than adults have in proportion to their body weights. Therefore neonates and young infants who receive gadolinium contrast on a dose-per-kilogram basis will have blood gadolinium concentrations of only one half that in adults after equilibration. This fact argues against using a lower dose per kilogram in infants than in adults, even though the serum half-life is prolonged. Clinical experience by our group and others has demonstrated that the adult dose of gadolinium contrast (0.1 mmol/kg for most extracellular agents) is also appropriate in infants and children.
 
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