Effect of Magnesium Sulphate Pre-exposure on Oxytocin-induced Contractility in Desensitized Human Myometrium - an in Vitro Study

• Status: Completed
• Trial end date: 2017-04-01

Summary

Postpartum hemorrhage (PPH) is the loss of more than 500ml of blood within 24 hours after delivery. It is a major cause of maternal morbidity and mortality across the globe.

Oxytocin is a naturally-occurring hormone that causes the uterus to contract, thereby causing labor. A synthetic form of oxytocin is used in obstetric medicine in the same way. It causes the uterus to contract by acting at the oxytocin receptor (OTR). It is used for both the prevention and the treatment of PPH. By causing the uterus to contract, it constricts the blood vessels within it, thus reducing bleeding.

Oxytocin is also used to augment labor in women with slow labor progression. Desensitization of the OTR after prolonged exposure to oxytocin occurs, leading to reduced contractions of the uterus with the same doses of oxytocin. This has been demonstrated in previous studies done by the investigators. The resultant need for a higher oxytocin dose to cause adequate uterine contraction has also been demonstrated in laboring women having received oxytocin for labor augmentation.

Magnesium sulphate (MgSO4) is widely used within obstetric medicine. It is used for seizure prevention and treatment in preeclampsia and eclampsia, and is used for fetal neuroprotection in preterm labor, to reduce the risk of cerebral palsy. It is well-known to have a relaxant effect on uterine muscle, and as such, has been used as a tocolytic agent in preterm labour to prevent premature contractions and premature delivery. The effect of MgSO4 on contractions in oxytocin pre-treated myometrium has not been fully elucidated with human lab studies. There are suggestions it may lead to increased oxytocin requirements or increased postpartum hemorrhage (PPH) in preeclamptic patients. This bears significance in the preeclamptic and eclamptic populations who are likely to be receiving MgSO4 in combination with oxytocin.

The investigators hypothesize that MgSO4 will reduce uterine contractions in oxytocin pre-treated myometrium, as well as untreated myometrium, and higher oxytocin doses will be needed to produce equivalent contractions. This will help us to better understand the implications of the use of these drugs together in the clinical setting.

• Phase: N/A

Details

• Lead Sponsor: Samuel Lunenfeld Research Institute, Mount Sinai Hospital
• Treatments: Magnesium Sulfate; Oxytocin; Pharmaceutical Solutions