Maternal Hemodynamic Effects of Medical Gases and Uterotonics in Obstetrics

Abstract: Aim of study: To elucidate the hemodynamic effects of pharmaceutical and medical interventions during pregnancy and childbirth on the mother.Introduction: Oxytocin, oxygen, and nitrous oxide are pharmaceuticals very commonly used in labor and delivery. These pharmaceuticals have known cardiovascular adverse effects. Some of these effects might be detrimental for the mother in case of major blood loss or preexisting cardiovascular disease, but the full extent of these effects is not known. The newer uterotonic carbetocin may have another adverse effect profile.Study population: Pregnant women during elective cesarean section; first trimester pregnant women during scheduled surgery for suction curettage; and pregnant and nonpregnant women during the third trimester.Methods: Cardiovascular effects are measured through ECG, blood pressure, oxygen saturation, and photoplethysmographic pulse wave analysis. By measuring the light absorption of infrared light through the finger, a waveform is obtained, from which it is possible to calculate indices of vascular stiffness and cardiac performance.Results: Oxytocin and carbetocin both have similar effects of vasodilation and blood pressure decrease. Pregnant women experienced more profound subjective side effects from nitrous oxide inhalations than nonpregnant controls. Oxygen alone and in a mix with nitrous oxide have vasoconstrictive and possible negative inotropic effects. These effects were more profound in pregnant women than in nonpregnant controls.Conclusion: The abovementioned medical interventions have cardiovascular effects that are sometimes quite profound. These effects can be shown with a simple and pain-free methodology. Carbetocin seems to have similar cardiovascular adverse effects compared to Oxytocin. Prudence should be taken when administering these drugs to compromised mothers. Both nitrous oxide and oxygen have vasoconstrictive and possible negative inotropic effects that were more prominent in pregnant women than in nonpregnant controls. Some of the effects seen from nitrous oxide might be due to the oxygen fraction in the gas mixture. Awareness of cardiovascular effects is important when treatment of the mother with oxytocin receptor agonists as well as with nitrous oxide and oxygen is considered. Oxygen treatment should not be used without a precise indication.