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Preterm infants have a shorter plasma heparin half-life and greater clearance compared to adults, necessitating adjusted dosing. This impacts neonatal intensive care unit (NICU) heparin therapy.
Area of Science:
- Pharmacology
- Neonatology
- Biochemistry
Background:
- Heparin is crucial for managing thromboembolic events in neonates.
- Understanding heparin pharmacokinetics in preterm infants is vital for safe and effective anticoagulation.
Purpose of the Study:
- To compare the pharmacokinetics of heparin in preterm neonates with those in normal adults.
- To investigate the impact of gestational age on heparin half-life, volume of distribution, and clearance in neonates.
Main Methods:
- Bolus infusions of sodium heparin were administered to 25 preterm neonates and 8 adults.
- Plasma heparin levels were measured at various time points using chromogenic and one-stage clotting assays.
- Pharmacokinetic parameters including half-life (T1/2), volume of distribution (Vd), and clearance (CI) were calculated.
Main Results:
- Newborn infants exhibited a significantly shorter plasma heparin half-life (33.0–41.6 min) compared to adults (63.3 min).
- The volume of distribution for heparin was larger in neonates and inversely correlated with gestational age.
- Heparin clearance was substantially greater in all newborn groups than in adults.
Conclusions:
- Preterm neonates demonstrate distinct heparin pharmacokinetics, characterized by a shorter half-life, larger Vd, and increased clearance compared to adults.
- Gestational age influences heparin Vd in neonates.
- These findings suggest that standard adult heparin dosing may not be appropriate for preterm infants, highlighting the need for individualized dosing strategies in neonatal intensive care.
Abstract:
Twenty-five preterm newborns were given bolus infusions of sodium heparin (100 units/kg) and plasma heparin levels were assayed at 5, 20, 40, 90, and 150 min. Eight normal adults received a 75 units/kg bolus of heparin and levels were assayed at 5, 30, 60, 120, 180, and 240 min. In comparison with the adult data (mean adult plasma heparin half life (T1/2) = 63.3 min), the newborn infants demonstrated a significantly shorter plasma heparin half life (T1/2 = 35.5 min in group I, 33 to 36 wk gestation; 35.5 min in group II, 29 to 32 wk gestation; and 41.6 min in group III, 25 to 28 wk gestation), as demonstrated by a chromogenic heparin assay. The newborn groups, had a larger volume of distribution (Vd) of heparin which varied inversely with gestational age (Vd =36.6 ml/kg in the adults, 57.8 ml/kg in group I, 73.3 ml/kg in group II, and 81.0 ml/kg in group III babies. Heparin clearance (CI) was significantly greater in all newborn groups when compared with the adult (CIadult = 0.43 ml/kg/min; ClGrIII = 1.49 ml/kg/min). A one-stage clotting assay for heparin generated similar results, although infant plasma heparin levels were slightly higher by this assay. Before heparin administration, the mean antithrombin III antigen (AT-III Ag) of the babies was 26.5% of normal adult and was not furthur decreased 90 min after the heparin bolus.