This study will investigate the effects of drugs called "uterotonics" that help with the contraction of the uterus after a baby is born. This uterine contraction is very important to stop the bleeding after delivery. An uncontracted uterine state is called "uterine atony", which can lead to an excessive amount of post-delivery bleeding. Carbetocin is an uterotonic drug that works well to prevent post-delivery bleeding. In some cases, carbetocin is not enough to contract the uterus, and ongoing bleeding continues. When that happens, there are other uterotonic medications that can be used. In this study, we aim to find which uterotonic drug, amongst those available (oxytocin, carbetocin, ergometrine or carboprost), is more effective to lower the risk of post-delivery bleeding once carbetocin has already been administered.
This study will be done by using a very small sample of uterine tissue, taken from the incision site, following delivery by cesarean section. The sample is taken to the laboratory and will be exposed to carbetocin followed by other uterotonic drugs. The information obtained from this study will help modify the treatment for uterine atony and post-delivery bleeding to lower the risk further.
Patients who give written consent to participate in this study
Patients with gestational age 37-41 weeks
Non-laboring patients, not exposed to exogenous oxytocin
Patients requiring elective primary or first repeat CD
Patient refusal
Patients who require general anesthesia
Patients in labour and those receiving oxytocin for induction of labour
Emergency CD
Parallel
Carbetocin
DrugCarbetocin first bolus 10-8 M (equivalent to 100 mcg) will be added to the muscle bath to create ex-vivo environment similar to Cesarean delivery, and after 20 minutes the baths will be washed three time with physiological salt solution (PSS).
Oxytocin
DrugOxytocin 10-5M will be added to all strips for 2 hours to induce desensitization.
Carbetocin
DrugIncreasing concentrations of carbetocin in a pattern of 1 log molar increase every 10 min, from 10-5 M to 10-5 M
Oxytocin
DrugIncreasing concentrations of oxytocin from 10-10 M to 10-5 M
Ergonovine
DrugIncreasing concentrations of ergometrine from 10-10 M to 10-5 M
Carboprost
DrugIncreasing concentrations of carboprost from 10-10 M to 10-5 M
Motility index
Motility index (MI) is a calculated outcome, based on the formula: frequency/(10 x amplitude). Frequency and amplitude are secondary outcome measures as described below. The analysis is undertaken by attaching myometrial strips between an isometric force transducer and the base of an organ bath chamber.
Amplitude of contraction
The maximum extent of uterine muscle contraction, measured in grams (g). The analysis is undertaken by attaching myometrial strips between an isometric force transducer and the base of an organ bath chamber.
Frequency of contraction
The number of contractions in uterine muscle (myometrium) over 10 minutes, spontaneously and in response to an agonist. The analysis is undertaken by attaching myometrial strips between an isometric force transducer and the base of an organ bath chamber.
Integrated area under response curve (AUC)
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