title: Fetoscopy under gas amniodistension: pressure-dependent influence of helium vs nitrous oxide on fetal goats.
abstract: OBJECTIVE
  Recently, gas amniodistension has been advocated for fetoscopic surgery to employ ergonomics similar to laparoscopy. However, neither the optimal type of gas nor its physiological influence on the fetus have been clearly outlined yet. This study investigates the impact of helium (HE) vs nitrous oxide (N2O) on fetal goats during fetoscopy.
  
  
  METHODS
  We insufflated either HE or N2O in 12 pregnant goats (15 fetuses; HE = 7, N2O = 8), then increased the pressures from 0, 4, 7, to 10 mm Hg in 30-minute intervals and recorded the fetal and maternal vital parameters. Finally, whole-body computed tomography to asses for intracorporeal gas was performed.
  
  
  RESULTS
  All fetuses survived. Mean fetal vital signs showed no significant differences between HE or N2O at specific pressure levels. In detail, HE/N2O at 0 vs 10 mm Hg caused a fetal temperature decrease (32.9 degrees C/33.2 degrees C vs 32 degrees C/32.5 degrees C), heart rate increase in the N2O group (100/102 vs 102/121 beats per minute), and no significant change in arterial pressure (45.8/48.3 vs 53.7/46.7 mm Hg). The PO2 was adequate (3.7/3.3 vs 3.7/2.9 kPa), whereas the pH remained unchanged (7.4/7.3 vs 7.3/7.3). However, fetal pCO2 was elevated in the N2O group before insufflation (5.5/7.2 vs 6.8/8.0 kPa) owing to maternal hypoventilation (maternal PCO2: 4.9/5.8 vs 5.0/5.4 kPa), correction of which was slower in the fetus than in the maternal animal. Computed tomography ruled out intracorporeal gas accumulation.
  
  
  CONCLUSIONS
  Neither HE nor N2O impose significant physiological harm for the fetus. Heating of the gas and maternal anesthesia seem essential. Considering the potential teratogenicity of N2O, however, HE could be the favorable environment for fetoscopic procedures under gas amniodistension.
authors.affiliation: Department of Pediatric Surgery, University of Leipzig, Childrens' Hospital, 04317 Leipzig, Germany. holger.till@medizin.uni-leipzig.de
authors.forename: Holger
authors.initials: H
authors.lastname: Till
authors.forename: Chung Kwong
authors.initials: CK
authors.lastname: Yeung
authors.forename: Wendy
authors.initials: W
authors.lastname: Bower
authors.forename: Yimin
authors.initials: Y
authors.lastname: Shi
authors.forename: Q
authors.initials: Q
authors.lastname: Tian
authors.forename: W
authors.initials: W
authors.lastname: Chu
authors.forename: H Y
authors.initials: HY
authors.lastname: Yip
authors.forename: J
authors.initials: J
authors.lastname: Tse
mesh_terms: D000650:Amnion / Q000502:physiology*; D000818:Animals; D005260:Female; D005332:Fetoscopy; D006041:Goats; D006371:Helium; D006863:Hydrogen-Ion Concentration; D007327:Insufflation / Q000379:methods*; D009609:Nitrous Oxide; D011247:Pregnancy; D011897:Random Allocation; D012307:Risk Factors
chemical_list: D006371:Helium; D009609:Nitrous Oxide