The incidence of post-partum hemorrhage is ~ 5%. The major causes are placenta previa, placenta accreta, abruptio placentae (abruption), uterine rupture (rupture), uterine atony, or a retained placenta.
Podcast on Obstetric Anesthesiology, obstetric hemorrhage: Discussion with Cynthia Wong from April 2010
Responsible for 0.9% of maternal mortality but 17-26% of perinatal mortality (i.e., while potentially dangerous for the mother, is extremely threatening to the neonate). Characterized as painless vaginal bleeding at 32 weeks or later, i.e., normally does not occur until month 7. Diagnosis confirmed by ultrasound, after which delivery must occur via Cesarean section – because the risk of catastrophic bleeding is above normal, two large-bore IVs must be in place, ketamine should be available, and neonatal resuscitation should be planned.
Accreta = onto the myometrium, increta = into the myometrium, and percreta = through the myometrium. Incidence is 1:2500 overall, although up to 7% in patients with a placenta previa, even higher in women with a previous Cesarean section (as high as 31% with one previous incision and > 50% with two or more) [Stoelting RK. Basics of Anesthesia, 5th ed. Elsevier (China), p. 497, 2007]. Massive blood loss is common (2000-5000 mL), 20% of women will develop a coagulopathy, and 30-72% will require a hysterectomy. [Stoelting RK. Basics of Anesthesia, 5th ed. Elsevier (China), p. 497, 2007]
Huge volume losses can occur and because of the anatomy, may go unnoticed. Vaginal delivery is a reasonable option in the hemodynamically stable patient (provided that the placenta is not located near the os) as blood loss is, on average, less than with Cesarean section.
Fetal bradycardia is the most sensitive sign. Uterine rupture should always be considered in the differential diagnosis of a bleeding parturient. Associated signs and symptoms include severe abdominal pain, hypotension, and loss of fetal heart tones.
Incidence is 0.5-2.5% in attempts at post-Cesarean vaginal delivery (higher if labor is induced, only 0.16% in post-Cesarean women who do not attempt labor, i.e., an up to 10-fold increase if labor is induced) – note that 60% of women with a prior Cesarean delivery will at least attempt labor [Lydon-Rochelle M et al. NEJM 345: 3, 2001]. Any patient who attempts to labor following a Cesarean section should be considered an operative candidate.
Most common cause of postpartum hemorrhage. Treated with synthetic oxytocins (ex. oxytocin injection, Pitocin®), which do NOT contain vasopressin – if given rapidly (ex. 10 U Pitocin® rapidly, despite that the manufacture recommends only 5 U slowly), these agents can cause vasodilation/hypotension and tachycardia [Pinder AJ et al. Int J Obstetr Anesth 11: 156, 2002]. 10 – 15 units should be given in 500 cc of crystalloid, slowly titrated to effect. If unhelpful, consider methylergonovine (0.2 mg IM, contraindicated in preeclampsia), prostaglandin F2α (0.25 mg IM, may increase airway resistance), or misoprostol (prostaglandin E1 analog).
- 10-20 U Pitocin® infusion over 10 mins
- Methylergonovine 0.2 mg IM (contraindicated in preeclampsia)
- Prostaglandin F2α (0.25 mg IM, may increase airway resistance)
About 1% of placentas are retained. Sometimes removal can be accomplished manually, with IV sedation or inhalation of nitrous oxide. If uterine relaxation is necessary, 50-150 ucg of intravenous nitrogylcerin can be administered. Occasionally, general anesthesia is required.