Details

Autor(en) / Beteiligte

• Onwochei, Desire N.
• Carvalho, Jose C. A.
• Luca, Alice
• Kingdom, John
• Balki, Mrinalini

Titel

Effect of magnesium sulfate on oxytocin-induced contractility in human myometrium: an in vitro study

Ist Teil von

• Canadian journal of anesthesia, 2017-07, Vol.64 (7), p.744-753

Ort / Verlag

New York: Springer US

Erscheinungsjahr

2017

Quelle

SpringerLink

Beschreibungen/Notizen

• Purpose The purpose of this study was to determine the contractile patterns induced by oxytocin in myometrium exposed to magnesium sulfate (MgSO 4 ). We hypothesized that MgSO 4 pretreatment would reduce oxytocin-induced myometrial contractions in both oxytocin-naïve and oxytocin-desensitized myometrium. Methods In this prospective in vitro study, myometrial samples were obtained from 26 women undergoing elective Cesarean deliveries. Samples were divided into six groups. Four groups were apportioned to no pretreatment (control group), oxytocin 10 −5 M pretreatment (desensitization group), MgSO 4 3.5 mM pretreatment, and MgSO 4 3.5 mM + oxytocin 10 −5 M pretreatment. This was followed by dose-response testing to oxytocin 10 −10 to 10 −5 M in all four groups. Two additional groups included MgSO 4 3.5 mM pretreatment and MgSO 4 3.5 mM + oxytocin 10 −5 M pretreatment, followed by dose-response testing to oxytocin along with MgSO 4 3.5 mM. The outcomes were motility index (MI), as defined by the amplitude (g) × frequency of myometrial contractions (c) over ten minutes, and area under the curve (AUC). Results In oxytocin-naïve myometrium, the mean (standard error [SE]) MI was not affected by MgSO 4 pretreatment [3.31 (0.20) √g⋅c/10 min] as compared with control ( P = 0.88), even when MgSO 4 was continued during dose-response testing [2.50 (0.19) √g⋅c/10 min; P = 0.41]. In the oxytocin-desensitized model, mean (SE) MI was not affected by MgSO 4 pretreatment [2.60 (0.21) √g⋅c/10 min; P = 0.68], but when MgSO 4 was continued during the dose-response period, the MI was significantly reduced compared with control [1.89 (0.13) √g⋅c/10 min; P < 0.001]. The results for AUC were similar to MI, except for a significant reduction in oxytocin-naïve myometrium when MgSO 4 was continued during dose-response testing ( P = 0.02). Conclusion Magnesium sulfate pretreatment does not impair oxytocin-induced myometrial contractility in oxytocin-naïve or desensitized myometrium unless it is continued during oxytocin dose-response testing. These results suggest that its tocolytic effect is likely dependent on an extracellular mechanism. The study was registered with ClinicalTrials.gov, number NCT02647268.