Haemodynamic Effects of Oxytocin (Syntocinon®) and Methyl Ergometrine (Methergin®) on the Systemic and Pulmonary Circulations of Pregnant Anaesthetized Women

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Abstract
Hemodynamic effects of oxytocin (Syntocinon) and methyl ergometrin (Methergin) were studied in 9 healthy females in the 1st trimester of pregnancy. Patients were anesthetized with sodium thiomebumal, pethidine and pancuronium bromide and ventilated on a Manley respirator. Oxytocin [IOIU] given as an i.v. bolus induced a fall in femoral arterial pressure of 40%, systemic resistance 59% and pulmonary resistance 44% 30 s after injection. Heart rate increased 31% and stroke volume 17%, so that cardiac output increased by 54%. Pulmonary arterial pressure and wedge pressure were increased by 33% and 35%, respectively, 150 s after injection. No changes were seen in hemodynamic parameters during infusion of 80 mU oxytocin for 10 min. Methergin [0.2 mg] brought about an increase in femoral arterial pressure of 11%, pulmonary arterial pressure 27% and wedge pressure 31%, with no changes in other measured parameters. Use of oxytocic drugs in patients with compromised circulation is discussed.