Oxytocin Dosage. A 1-mL ampule containing 10 units of oxytocin usually is diluted into 1000 mL of a crystalloid solution and administered by infusion pump. A typical infusate consists of 10 or 20 units, which is 10,000 or 20,000 mU or one or two 1-mL vials, respectively, mixed into 1000 mL oflactated Ringer solution. his mixture results in an oxytocin concentration of 10 or 20 mU/mL, respectively. To avoid bolus administration, the infusion should be inserted into the main intravenous line close to the venipuncture site.
Oxytocin is generally very successful when used to stimulate labor. In one large Cochrane metaanalysis, oxytocin was compared with expectant management, and fewer women-8 versus 54 percent-failed to deliver vaginally within 24 hours
Induction and Augmentation of Labor 509
TABLE 26-3. Various Low-and High-Dose Oxytocin Regimens Used for Labor Induction
Low-dose 0.5-1.5 15-40 2 15 4,8,12,s16,20,25,30 4.5 15-30 4.5 aUterine tachysystole is more common with shorter intervals. bWith uterine tachysystole and after oxytocin infusion is discontinued, It is restarted at one half the previous dose and then increased at 3 mU/min incremental doses.
Data from Merrill, 1999; Satin, 1992, 1994; Xenakis, 1995.
with oxytocin (Alfirevic, 2009). This analysis studied diferent oxytocin dosing regimens.
Oxytocin Regimens. Several evidence-based regimens for labor stimulation are now recommended by the American College of Obstetricians and Gynecologists (2016). hese and others are shown in Table 26-3. Initially, only variations of low-dose protocols were used in the United States. Subsequently, O'Driscoll and colleagues (1984) described their Dublin protocol for the active management of labor that called for oxytocin at a starting dosage of 6 mU/min and advanced in 6-mU/min increments. Subsequent comparative trials during the 1990s studied high-dose (4 to 6 mU/min) versus conventional low-dose (0.5 to 1.5 mU/min) regimens, both for labor induction and for augmentation.
From Parkland Hospital, Satin and associates (1992) evaluated an oxytocin regimen using an initial and incremental dosage of 6 mU/min compared with one using 1 mU/min. Increases at 20-minute intervals were provided as needed. Among 1112 women undergoing induction, the 6-mU/min regimen resulted in a shorter mean admission-to-delivery time, fewer failed inductions, and no cases of neonatal sepsis. Among 1676 women who had labor augmentation, those who received the 6-mU/min regimen had a shorter duration-to-delivey time, fewer forceps deliveries, fewer cesarean deliveries for dystocia, and lower rates of intrapartum chorioamnionitis or neonatal sepsis. With this protocol, uterine tachysystole was managed by oxytocin discontinuation followed by resumption when indicated and at half the stopping dosage. hereafter, the dosage was increased at 3 mU/min when appropriate, instead of the usual 6-mU/min increase used for women without tachysystole. No adverse neonatal efects were observed.