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Placental transfer and pharmacokinetics of thiopentone in newborn infants
  1. Elisabeth Norman1,
  2. Per Westrin2,
  3. Vineta Fellman1,3
  1. 1Department of Paediatrics, Lund University, Lund, Sweden
  2. 2Department of Paediatric Anaesthesia, Lund University, Lund, Sweden
  3. 3Department of Paediatrics, University of Helsinki, Helsinki, Finland
  1. Correspondence to Dr Elisabeth Norman, Neonatal Intensive Care Unit,University Hospital, SE-221 85 Lund, Sweden; elisabeth.norman{at}med.lu.se

Abstract

Background and Objectives Thiopentone, a short-acting barbiturate, has been introduced as premedication for intubation in newborn infants. The objectives of this study were to assess the pharmacokinetics of thiopentone in newborn infants, and to unravel whether placental transfer of the drug should be taken into account if administered to infants exposed to it during delivery.

Methods Plasma concentrations were assessed with high-pressure liquid chromatography in samples from delivering mothers (n=27) receiving a median dose of 5.5 mg/kg (range 3.8–7.7) thiopentone for Caesarean section in gestational week 37.6 (range 25.7–41.4) and from corresponding umbilical cord blood (n=28). In infants (n=30) born at 35.4 weeks gestation (range 27.9–42.0) undergoing surgery at a median postnatal age of 24.5 h (range 4–521), repeated blood levels were assessed after administering a dose of 3 mg/kg thiopentone on clinical indication before intubation (seven samples per infant from 5 min to 48 h after administration).

Results The umbilical/maternal concentration ratio was 0.7, the mean concentration of thiopentone was 55.7 µmol/l (SD±15.3) in mothers and 39.3 µmol/l (SD±12.5) in venous cord blood. In newborn infants undergoing surgery, the terminal half-life of thiopentone was 8 h (interquartile range (IQR) 2.5–10.8), and clearance 0.092 l/min per kg/postnatal age in days (IQR 0.02–0.1).

Conclusions Thiopentone might be used as premedication for short-lasting intubation after birth, for example, for surfactant administration. During the first 4 h after birth the dose needs to be adjusted for maternal dosage as well as for the weight of the infant.

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Footnotes

  • Funding The present study was supported by grants from the Region Skåne (regional medical research grants), Ekdahls and Elsa Lundberg and Greta Flerons Foundations.

  • Competing interests None.

  • Patient consent Obtained from the parents.

  • Ethics approval This study was conducted with the approval of the Regional Ethics Committee, Lund University, Lund, Sweden.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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