Utero tonics may be given before or after placental expulsion without afecting rates of postpartum hemorrhage, placental retention, or third-stage labor length (Soltani, 2010). If they are given before delivery of the placenta, however, they may entrap an undiagnosed, undelivered second (Win. hus, abdominal palpation should conirm no additional fetuses. Notably, this concern is less relevant with current widespread sonography use.
Synthetic oxytocin is identical to that produced by the posterior pituitary. Its action is noted at approximately 1 minute, and it has a mean half-life of 3 to 5 minutes. When given as a bolus, oxytocin can cause profound hypotension. Secher and coworkers (1978) reported that an intravenous bolus of 10 units of oxytocin caused a marked transient fall in blood pressure with an abrupt increase in cardiac output. Svansrrom and associates (2008) conirmed those findings. hese hemodynamic changes could be dangerous for women hypovolemic from hemorrhage or those with certain types of cardiac disease. Thus, oxytocin should be given as a dilute solution by continuous intravenous infusion or as an intramuscular injection.
Water intoxication can result from the antidiuretic action of high-dose oxytocin if administered in a large volume of electro lyte-free dextrose solution (Whalley, 1963). Thus, if oxytocin is to be administered in high doses for a considerable period of time, its concentration should be increased rather than increas ing the infusion flow rate.
Despite the routine use of oxytocin, no standard prophylactic dose has been established for its use following either vaginal or cesarean delivery. Our practice is to add 20 units (2 mL) of oxytocin per liter of infusate. his solution is administered after delivery of the placenta at a rate of 10 to 20 mUmin-200 to 400 mU/min-for a few minutes until the uterus remains irmly contracted and bleeding is controlled. he infusion rate then is reduced to 1 to 2 mUmin until the mother is ready for transfer from the recovery suite to the postpartum unit. The infusion is usually then discontinued. For women without intravenous access, 10 units of intramuscular oxytocin are injected.
Ergonovine and methylergonovine have similar activity levels in myometrium, and only methylergonovine is currently manufactured in the United States. These ergot alkaloid agents do not provide superior protection against postpartum hemorrhage compared with oxytocin. \10reover, safety and tolerability are greater with oxytocin (Liabsuetrakul, 2011). For these reasons, ergot alkaloid agents are considered second-line for prevention of postpartum hemorrhage. If selected, a 0.2-mg dose of methylergonovine is slowly given intravenously in a period not less than 60 seconds to avoid sudden hypertension (Novartis, 2012). Methylergonovine is relatively contraindicated in the hypertensive woman.
Misoprostol is a prostaglandin E, analogue, which has proved inferior to oxytocin for postpartum hemorrhage prevention (Tun:alp, 2012). However, in resource-poor settings that lack oxytocin, misoprostol is suitable for hemorrhage prophylaxis and is given as a single oral 600-�g dose (Mobeen, 2011; World Health Organization, 2012). Notably, although oxytocin is preferred for prevention of hemorrhage, ergot alkaloids and prostaglandins playia greater role in postpartum hemorrhage treatment, discussed in Chapter 41 (p. 759).
• Manual Removal of Placenta