title: Effect of decreased fetal perfusion on placental clearance of volatile anesthetics in a dual perfused human placental cotyledon model.
abstract: Placental transfer of volatile anesthetics is a critical issue in managing fetal distress during cesarean section under general anesthesia. Using dual perfused human placental cotyledons obtained from parturients undergoing elective cesarean section (n = 5), we investigated the effect of decreased fetal perfusion on placental clearance of sevoflurane and isoflurane. Keeping the maternal flow rate fixed, fetal flow rate was consecutively decreased from 3 ml/min (control perfusion) to 2 ml/min (intermediate perfusion) and to 1 ml/min (hypoperfusion). Placental transfer was assessed by the clearance of anesthetics by the placenta, defined by the ratio of anesthetic concentration in fetal vein and maternal artery, multiplied by fetal flow rate. Placental clearance was compared between different fetal perfusion states and anesthetics. Hypoperfusion resulted in a lower clearance of sevoflurane and isoflurane compared with control (P = 0.002, P < 0.001) and intermediate (P = 0.04, P = 0.018) perfusion. Clearances of sevoflurane and isoflurane were comparable during control perfusion (P = 0.93), intermediate perfusion (P = 1.00), and hypoperfusion (P = 0.88). Thus, maintenance of volatile anesthetics at a marginally low concentration may not be necessary when fetal distress is observed during emergency cesarean delivery because placental transfer of volatile anesthetics decreases with decreasing fetal perfusion.
authors.affiliation: Department of Anesthesiology, Hyogo College of Medicine, 1-1 Mukogawa-cho, Nishinomiya, Hyogo, 663-8501, Japan, rueki@hyo-med.ac.jp.
authors.forename: Ryusuke
authors.initials: R
authors.lastname: Ueki
authors.forename: Tsuneo
authors.initials: T
authors.lastname: Tatara
authors.forename: Nobutaka
authors.initials: N
authors.lastname: Kariya
authors.forename: Noriko
authors.initials: N
authors.lastname: Shimode
authors.forename: Munetaka
authors.initials: M
authors.lastname: Hirose
authors.forename: Chikara
authors.initials: C
authors.lastname: Tashiro
mesh_terms: D000328:Adult; D018685:Anesthetics, Inhalation / Q000009:adverse effects / Q000378:metabolism*; D002585:Cesarean Section; D005260:Female; D005333:Fetus / Q000098:blood supply*; D006801:Humans; D007231:Infant, Newborn; D007530:Isoflurane / Q000378:metabolism; D008738:Methyl Ethers / Q000378:metabolism; D010920:Placenta / Q000098:blood supply / Q000378:metabolism*; D011247:Pregnancy; D012039:Regional Blood Flow / Q000187:drug effects; D000077149:Sevoflurane
chemical_list: D018685:Anesthetics, Inhalation; D008738:Methyl Ethers; D000077149:Sevoflurane; D007530:Isoflurane