Skip to main content Accessibility help

Nitrous oxide concentrations in maternal and fetal blood during Caesarean section

  • F. Karasawa (a1), A. Takita (a1), I. Fukuda (a1) and Y. Kawatani (a1)



Background and objective: There are little data on nitrous oxide (N2O) concentrations in neonatal blood at delivery. We investigated the effects of the time elapsing between the induction of anaesthesia and delivery (the I–D interval) on umbilical blood N2O concentrations.

Methods: Maternal and neonatal blood N2O concentrations were measured in 27 patients undergoing Caesarean section under N2O 67% anaesthesia. The duration of N2O administration (range 2–50 min) was arbitrarily divided into three groups (each n = 9): short (2–9 min), medium (9.1–14 min) and long duration (14.1–50 min).

Results: Compared with a rapid increase in the maternal arterial N2O concentration (48.9 ± 4.7%), the umbilical venous N2O concentration (17.9 ± 8.3%) rose slowly in the short duration group, whereas the N2O concentrations became more similar (61.6 ± 4.3 and 43.2 ± 10.0%, respectively) in the long duration group. The ratio of umbilical vein to maternal artery N2O concentrations correlated with the duration of N2O anaesthesia (r = 0.739), resulting in ratios of 0.37 ± 0.18, 0.61 ± 012 and 0.70 ± 0.13 for the short, medium and long duration groups, respectively. The Apgar score at 1 min correlated inversely with the duration of anaesthesia and with the umbilical vein N2O concentration (r = −0.457 and −0.423, respectively).

Conclusions: The data suggest that placental N2O transfer during Caesarean section is time-dependent and slower compared with maternal N2O uptake. They also suggest that the Apgar score is less affected by N2O administration when the I–D interval is shorter.


Corresponding author

Correspondence to: Fujio Karasawa, Department of Anaesthesiology, National Defense Medical College, Tokorozawa, Saitama 359-8513, Japan. E-mail:; Tel: +81 42 995 1692; Fax: +81 42 992 1215


Hide All


Santos AC, O'Gorman DA, Finster M. Obstetric anesthesia. In: Barash PG, Cullen BF, Stoelting RK, eds. Clinical Anesthesia, 4th edn. Philadelphia, USA: Lippincott Williams & Wilkins, 2001: 11411170.
Brownridge P. Obstetric anaesthesia and Caesarean section. In: Prys-Roberts C, Brown Jr BR, eds. International Practice of Anaesthesia, vol. 2. Oxford, UK: Butterworth-Heinemann, 1996: 2/98/113.
Stenger VG, Blechner JN, Prystowsky H. A study of prolongation of obstetric anesthesia. Am J Obst Gynec 1969; 103: 901907.
Marx GF, Joshi CW, Orkin LR. Placental transmission of nitrous oxide. Anesthesiology 1970; 32: 429432.
Cohen EN, Paulson WJ, Wall J, Elert B. Thiopental, curare and nitrous oxide anesthesia for cesarean section with studies on placental transmission. Surg Gynec Obstet 1953; 97: 456465.
Eger EI II. Uptake and distribution. In: Miller RD, ed. Anesthesia, 4th edn. Philadelphia, USA: Churchill Livingstone, 2000: 7495.
Mankwitz E, Brock-Utne JG, Downing JW. Nitrous oxide elimination by the newborn. Anaesthesia 1981; 36: 10141016.


Nitrous oxide concentrations in maternal and fetal blood during Caesarean section

  • F. Karasawa (a1), A. Takita (a1), I. Fukuda (a1) and Y. Kawatani (a1)


Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed