AJP Rep 2019 Apr 29;9(2):e177-e184. Epub 2019 May 29.
Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri.
To investigate differences in oxytocin (OXT) biodistribution between nonobese and obese parturients during labor. Patients with body mass index (BMI) of either ≥ 18 ≤ 24.9 kg/m ("nonobese") or ≥ 30 kg/m ("obese") undergoing elective induction of labor were included ( = 25 each). Blood samples were collected at baseline (T ), and 20 minutes after maximal OXT augmentation or adequate uterine contractions (T ) for OXT and oxytocinase assays. A mixed-model repeated-measures analysis of variance was used to test for group versus time interaction and analysis of covariance to detect a difference in OXT level at T . Data presented as mean ± standard deviation or median (interquartile range), with < 0.05 considered significant. The mean BMIs (kg/m ) were 22.1 ± 1.6 and 35.9 ± 5.1 in the nonobese and obese groups, respectively. No differences were observed in either the duration of OXT infusion, total dose of OXT, or plasma OXT (pg/mL) either at T or T . However, plasma oxytocinase (ng/mL) was significantly lower at T (1.41 [0.67, 3.51] vs. 0.40 [0.29, 1.12]; = 0.03) in the obese group. We provide preliminary evidence that the disposition of OXT may not be different between obese and nonobese women during labor.