From the Editor

Q: Following cesarean delivery, what is the optimal oxytocin infusion duration to prevent postpartum bleeding?

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A: High-reliability cesarean delivery requires a postoperative oxytocin infusion of 4 to 8 hours to reduce the risks of uterine atony and excessive postpartum bleeding


 

References

CASE: DISCONTINUED OXYTOCIN LEADS TO POSTPARTUM HEMORRHAGE
You have just completed a repeat cesarean delivery for a 41-year-old woman, now G2P2. You order an infusion of oxytocin, 20 U in 1 L lactated Ringer’s solution, to run at a rate of 125 mL/hr for 8 hours. Without informing you, the recovery room nurse discontinues the bag with the oxytocin solution and starts an infusion of lactated Ringer’s solution without oxytocin.

One hour later, you are called to the recovery room because your patient is having a postpartum hemorrhage (PPH). Physical examination shows that the uterus is boggy and above the level of the umbilicus. On ­bedside ­ultrasonography, the uterine cavity is demonstrated to contain minimal blood, and Doppler sonography does not demonstrate any vascular tissue within the uterine cavity. You diagnose uterine atony and initiate treatment. You massage the uterus, rapidly infuse 1 L crystalloid solution, place misoprostol 800 µg in the rectum, and reinitiate the oxytocin infusion. The uterine bleeding slows and then stops.

The following morning, the patient’s hematocrit has decreased from a preoperative value of 37% to 21%.

Could this case of PPH have been prevented?

Cesarean delivery is one of the most commonly performed major operations in developed countries. More than 1,250,000 cesarean deliveries are performed annually in the United States. In 2012, there were 3,952,937 births and a cesarean delivery rate of 32.8%.1 It is an important goal of obstetric care providers to continuously improve our approach to cesarean delivery in order to minimize the surgical risks of this procedure. Evidence-based, standardized protocols for cesarean delivery are critical to ensuring high- reliability surgical outcomes.

A key gap in cesarean delivery protocols is the lack of a nationwide, standardized approach to reducing the risk of postoperative bleeding by maintaining a continuous infusion of oxytocin in the hours immediately following cesarean delivery.

OXYTOCIN: A CRITICAL INTERVENTION TO PREVENT PPH
More than half of all maternal deaths occur in the 24 hours following delivery, with the most common cause being PPH.2 In addition to death, serious complications of PPH include coagulopathy, shock, emergency hysterectomy, transfusion complications, respiratory distress, and pituitary necrosis. Most cases of PPH that occur within 24 hours of delivery are caused by uterine atony.3 Other causes include retained products of conception, placenta accreta, infection, coagulation defects, and amniotic fluid embolism.

Administering a uterotonic such as oxytocin at the time of delivery reduces the risk of PPH by approximately 66% and the risk of maternal blood transfusion by about 65%.4 In order to prevent uterine atony and PPH, oxytocin should be routinely administered following birth of the baby or after delivery of the placenta. Appropriate doses following vaginal delivery are oxytocin 10 U administered intramuscularly or 10 U administered as a slow intravenous (IV) infusion.5 The onset of action of oxytocin is approximately 2 to 5 minutes after an intramuscular dose and 1 minute after an IV dose.6

Related article: Routine use of oxytocin at birth: just the right amount to prevent postpartum hemorrhage Robert L. Barbieri, MD (Editorial, July 2012)

OXYTOCIN AND CESAREAN DELIVERY
Many clinical trials have reported that during a cesarean delivery, the routine administration of a uterotonic agent following birth of the baby reduces the risk of uterine atony and excessive bleeding. Three uterotonics: oxytocin, misoprostol, and carbetocin (a long-acting oxytocin analogue, see SIDEBAR), have been reported to reduce the risk of excessive bleeding during cesarean delivery.7 Oxytocin is the uterotonic most commonly used during cesarean delivery in developed countries.

Related article: A new (to the US) first-line agent for heavy menstrual bleeding Robert L. Barbieri, MD (Editorial, October 2010)

In the United States, there is no standardized oxytocin regimen for prevention of uterine atony and hemorrhage at cesarean delivery. The most common regimen is to add 10–40 U of oxytocin in 1 L crystalloid solution and initiate the oxytocin infusion following delivery of the baby. Initially, the infusion is run at a rapid rate. Once the obstetrician reports that there is adequate uterine tone, the infusion rate is slowed to one that maintains uterine tone.

Some clinicians administer a single bolus of oxytocin following birth of the baby. However, a bolus of oxytocin commonly causes hypotension and, less commonly, ST segment changes on the electrocardiogram (EKG) suggestive of cardiac ischemia.8–10Many experts recommend against administering one large bolus of oxytocin over a short period of time and favor a continuous infusion.

At cesarean delivery, the minimum infusion rate of oxytocin that has been reported to avoid most cases of uterine atony, as reported by the obstetrician immediately following delivery, is approximately oxytocin 0.3 U/min.11 Oxytocin infusion rates of 0.2 U/min and 0.1 U/min were associated with uterine atony rates of 21% and 40%, respectively. An infusion rate of oxytocin 0.3 U/min can be achieved by the administration of 20 U of oxytocin in 1 L crystalloid solution at a rate of 15 mL/min until uterine tone is achieved. The oxytocin dose then can be titrated to maintain adequate uterine tone. Following completion of surgery, uterine tone can be maintained with a low-dose continuous infusion of oxytocin.

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