Effects of Carbetocin and Oxytocin Used in Cesarean Sections on Postoperative Pain

Postpartum hemorrhage (PPH) is one of the most important causes of perioperative maternal deaths. Oxytocin and carbetocin are the most important uterotonic agents used for PPH. Oxytocin has a half-life of 4-10 minutes (min) and can provide continuous uterotonic properties through infusion. Carbetocin, which has been used increasingly in recent years, is a synthetic analogue of oxytocin and has a strong uterotonic effect on oxytocin receptors. Oxytocin, which is used in PPH prophylaxis and management in cesarean delivery, has some maternal side effects depending on the rate of administration. These are cardiovascular effects, nausea, vomiting, headache and allergic reactions. Since it is structurally similar to vasopressin, water retention in the body and hyponatremia, convulsions and coma can be seen, although rarely. The most common cardiac effects after oxytocin administration are dose-dependent hypotension and tachycardia. Smooth muscle relaxation caused by stimulation of calcium-dependent nitrite oxide is held responsible for hypotension.[3] Carbetocin, a long-acting oxytocin analog, has similar side effects and further research is needed on its effectiveness.

There are potential studies supporting that the oxytocinergic system affects pain perception. Oxytocin released into the central nervous system plays an important role in the transmission and modulation of pain signals. Glutamatergic activation of oxytocin in the dorsal root ganglia results in GABAergic inhibition of Aδ and C fibers that play a role in nociception. Carbetocin is also thought to have similar effects in analgesia. Although there are studies showing that carbetocin reduces postoperative analgesic use compared to oxytocin , there is no clear consensus in the literature on this subject. The studies conducted by De Bonis et al. and Gawecka et al. were guiding in designing this study. While De Bonis et al. found that carbetocin reduces analgesic consumption, Gawecka et al. could not show a significant difference between the two agents.

In this study, the investigators aim to contribute to the literature by comparing the analgesic activities of oxytocin and carbetocin to observe the differences in hemodynamic and other side effects of these two agents.