Thiopentone and Etomidate Concentrations in Maternal and Umbilical Plasma, and in Colostrum

Abstract

We have measured concentrations of etomidate and thiopentone in maternal plasma, umbilical venous plasma and colostrum after induction of anaesthesia in 40 patients undergoing Caesarean section. Mean plasma etomidate concentration declined rapidly (1242.0 ng ml-1 at 5 min, 434.0 ng ml-1 at 15 min, 64.2 ng ml-1 at 30 min, 7.0 ng ml-1 at 60 min and undetectable 2 h after the injection). Mean plasma concentrations of thiopentone declined more slowly (6.09 micrograms ml-1 at 5 min, 2.64 micrograms ml-1 at 2 h, 1.35 micrograms ml-1 at 4 h, 0.86 microgram ml-1 at 9 h and 0.59 micrograms ml-1 at 12 h). Mean umbilical venous thiopentone concentration was 4.72 micrograms ml-1, whereas the thiopentone concentration in the maternal sample at 5 min was 6.09 micrograms ml-1, giving an umbilical:maternal vein ratio of 1:1.3. Mean umbilical etomidate concentration was 51.7 ng ml-1 and the corresponding maternal vein sample (5 min) was 1242.0 ng ml-1 (P < 0.001), giving an umbilical:maternal vein ratio of 1:24. Mean concentrations of thiopentone in colostrum were 1.98 micrograms ml-1 at 30 min, 0.91 microgram ml-1 at 4 h and 0.59 microgram ml-1 at 9 h, colostrum:plasma ratios at 4 h and 9 h being 0.67 and 0.68, respectively. Mean concentrations of etomidate in colostrum were 79.3 ng ml-1 at 30 min and 16.3 ng ml-1 at 2 h, being undetectable at 4 h. The colostrum:plasma etomidate concentration ratio was 1.2 at 30 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Placental transfer and pharmacokinetics of thiopentone in newborn infants

“…Placental transfer expressed as the fetal/maternal concentration ratio after a single dose exposure has in previous studies on term infants been 0.43–0.96,30–32 which is in agreement with our result in a cohort that also included preterm infants from 25 gestational weeks on.…”

“…In the 1990s thiopentone was studied regarding protein binding in neonatal serum27 and pharmacokinetics in the adult and paediatric populations 28. In the perinatal period, thiopentone has mainly been studied in full-term infants exposed to maternal anaesthesia, and some data are available on placental transfer 29–32. However, in the growing population of preterm infants, delivered by Caesarean sections and exposed to maternal anaesthetics, no studies have been performed.…”

Pharmacokinetic Optimisation of General Anaesthesia in Pregnancy

“…A maternal induction dose of etomidate 0.4 mg/kg still gave satisfactory neonatal Apgar scores and relatively low umbilical concentrations of etomidate (Crozier et al 1993;Gregory & Davidson 1991). Concentrations in colostrum also declined rapidly (Esener et al 1992).…”

Breastfeeding after Anesthesia: A Review for Anesthesia Providers Regarding the Transfer of Medications into Breast Milk

“…The rapid clearance of etomidate suggests etomidate may be safely used when clinically appropriate for breastfeeding mothers. 14 3. There are currently no human studies evaluating the transfer of ketamine to breast milk.…”