(妇产科学课件）05.3 邵勇 Postpartum Hemorrhage（英文）

1、( (妇产科学课件妇产科学课件05.3 05.3 邵勇邵勇 Postpartum Hemorrhage Postpartum Hemorrhage英文英文Background Postpartum hemorrhage (PPH) is the leading cause of maternal mortality. All women who carry a pregnancy beyond 20 weeks gestation are at risk for PPH and its sequelae. Although maternal mortality rates have decli

2、ned greatly in the developed world, PPH remains a leading cause of maternal mortality elsewhere.The direct pregnancy-related maternal mortality rate in the United States is approximately 7-10 women per 100,000 live births. National statistics suggest that approximately 8% of these deaths are caused

3、by PPH.1 In industrialized countries, PPH usually ranks in the top 3 causes of maternal mortality, along with embolism and hypertension. In the developing world, several countries have maternal mortality rates in excess of 1000 women per 100,000 live births, and World Health Organization statistics

4、suggest that 25% of maternal deaths are due to PPH, accounting for more than 100,000 maternal deaths per year.2 The most recent Practice Bulletin from the American College of Obstetricians and Gynecologists places the estimate at 140,000 maternal deaths per year or 1 woman every 4 minutes.3 The rate

5、 of PPH increased from 1.5% in 1999 to 4.1% in 2021, and the rate of atonic PPH rose from 1% in 1999 to 3.4% in 2021. The risk of total PPH with a morbidly adherent placenta was markedly higher.4Problem The definition of PPH is somewhat arbitrary and problematic. PPH is defined as blood loss of more

6、 than 500 mL following vaginal delivery or more than 1000 mL following cesarean delivery.5, 6 A loss of these amounts within 24 hours of delivery is termed early or primary PPH, whereas such losses are termed late or secondary PPH if they occur 24 hours after delivery. This article focuses on early

7、PPH. Estimates of blood loss at delivery are subjective and generally inaccurate. Studies have suggested that caregivers consistently underestimate actual blood loss. Another proposal suggests using a 10% fall in hematocrit value to define PPH, but this change is dependent on the timing of the test

8、and the amount of fluid resuscitation given.7 More importantly, the diagnosis would be retrospective, perhaps useful for research but not so in the clinical setting. Another consideration is the differing capacities of individual patients to cope with blood loss. A healthy woman has a 30-50% increas

9、e in blood volume in a normal singleton pregnancy and is much more tolerant of blood loss than a woman who has preexisting anemia, an underlying cardiac condition, or a volume-contracted condition secondary to dehydration or preeclampsia. For these reasons, various authors have suggested that PPH sh

10、ould be diagnosed with any amount of blood loss that threatens the hemodynamic stability of the woman. The diagnosis of PPH is usually reserved for pregnancies that have progressed beyond 20 weeks gestation. Deliveries at less than 20 weeks gestational age are spontaneous abortions. Bleeding related

11、 to spontaneous abortion may have etiologies and management in common with those for PPH.EpidemiologyFrequency The frequency of PPH is related to the management of the third stage of labor. This is the period from the completed delivery of the baby until the completed delivery of the placenta. Data

12、from several sources, including several large randomized trials performed in industrialized countries, indicate that the prevalence rate of PPH of more than 500 mL is approximately 5% when active management is used versus 13% when expectant management is used. The prevalence rate of PPH of more than

13、 1000 mL is approximately 1% when active management is used versus 3% when expectant management is used.8, 9 The increased frequency of PPH in the developing world is more likely reflected by the rates given above for expectant management because of the lack of widespread availability of medications

14、 used in the active management of the third stage.2 A number of factors also contribute to much less favorable outcomes of PPH in developing countries. The first is a lack of experienced caregivers who might be able to successfully manage PPH if it occurred. Additionally, the same drugs used for pro

15、phylaxis against PPH in active management of the third stage are also the primary agents in the treatment of PPH. Lack of blood transfusion services, anesthetic services, and operating capabilities also plays a role. Finally, the previously mentioned comorbidities are more commonly observed in devel

16、oping countries and combine to decrease a womans tolerance of blood loss.Etiology PPH has many potential causes, but the most common, by a wide margin, is uterine atony, ie, failure of the uterus to contract and retract following delivery of the baby. PPH in a previous pregnancy is a major risk fact

17、or and every effort should be made to determine its severity and cause. In a recent randomized trial in the United States, birthweight, labor induction and augmentation, chorioamnionitis, magnesium sulfate use, and previous PPH were all positively associated with increased risk of PPH.10In a large,

18、population-based study, significant risk factors, identified using multivariable analysis, were as follows:Retained placenta (OR 3.5, 95% CI 2.1-5.8)Failure to progress during the second stage of labor (OR 3.4, 95% CI 2.4-4.7)Placenta accreta (OR 3.3, 95% CI 1.7-6.4)Lacerations (OR 2.4, 95% CI 2.0-2

19、.8)Instrumental delivery (OR 2.3, 95% CI 1.6-3.4)Large-for-gestational-age (LGA) newborn (OR 1.9, 95% CI 1.6-2.4)Hypertensive disorders (OR 1.7, 95%CI 1.2-2.1)Induction of labor (OR 1.4, 95%CI 1.1-1.7)Augmentation of labor with oxytocin (OR 1.4, 95% CI 1.2-1.7). 11 PPH is also associated with obesit

20、y. In a study by Blomberg, the risk of atonic uterine hemorrhage rapidly increased with increasing BMI; in women with a BMI over 40, the risk was 5.2% with normal delivery and 13.6% with instrumental delivery.12 As a way of remembering the causes of PPH, several sources have suggested using the “4 T

21、 s as a mnemonic: tone, tissue, trauma, and thrombosis.15Tone Uterine atony and failure of contraction and retraction of myometrial muscle fibers can lead to rapid and severe hemorrhage and hypovolemic shock. Overdistension of the uterus, either absolute or relative, is a major risk factor for atony

22、. Overdistension of the uterus can be caused by multifetal gestation, fetal macrosomia, polyhydramnios, or fetal abnormality (eg, severe hydrocephalus); a uterine structural abnormality; or a failure to deliver the placenta or distension with blood before or after placental delivery. Poor myometrial

23、 contraction can result from fatigue due to prolonged labor or rapid forceful labor, especially if stimulated. It can also result from the inhibition of contractions by drugs such as halogenated anesthetic agents, nitrates, nonsteroidal anti-inflammatory drugs, magnesium sulfate, beta-sympathomimeti

24、cs, and nifedipine. Other causes include placental implantation site in the lower uterine segment, bacterial toxins (eg, chorioamnionitis, endomyometritis, septicemia), hypoxia due to hypoperfusion or Couvelaire uterus in abruptio placentae, and hypothermia due to massive resuscitation or prolonged

25、uterine exteriorization. Recent data suggest that grand multiparity is not an independent risk factor for PPH.Tissue Uterine contraction and retraction leads to detachment and expulsion of the placenta. Complete detachment and expulsion of the placenta permits continued retraction and optimal occlus

26、ion of blood vessels. Retention of a portion of the placenta is more common if the placenta has developed with a succenturiate or accessory lobe. Following delivery of the placenta and when minimal bleeding is present, the placenta should be inspected for evidence of fetal vessels coursing to the pl

27、acental edge and abruptly ending at a tear in the membranes. Such a finding suggests a retained succenturiate lobe. The placenta is more likely to be retained at extreme preterm gestations (especially 24 wk), and significant bleeding can occur. This should be a consideration in all deliveries at ver

28、y early gestations, whether they are spontaneous or induced. Recent trials suggest that the use of misoprostol for second trimester termination of pregnancy leads to a marked reduction in the rate of retained placenta when compared to techniques using the intrauterine instillation of prostaglandin o

29、r hypertonic saline.16 One such trial reported rates of retained placenta requiring D&C of 3.4% with oral misoprostol compared to 22.4% using intra-amniotic prostaglandin (p=0.002).17 Failure of complete separation of the placenta occurs in placenta accreta and its variants. In this condition, the p

30、lacenta has invaded beyond the normal cleavage plane and is abnormally adherent. Significant bleeding from the area where normal attachment (and now detachment) has occurred may mark partial accreta. Complete accreta in which the entire surface of the placenta is abnormally attached, or more severe

31、invasion (placenta increta or percreta), may not initially cause severe bleeding, but it may develop as more aggressive efforts are made to remove the placenta. This condition should be considered possible whenever the placenta is implanted over a previous uterine scar, especially if associated with

32、 placenta previa. All patients with placenta previa should be informed of the risk of severe PPH, including the possible need for transfusion and hysterectomy.Trauma Damage to the genital tract may occur spontaneously or through manipulations used to deliver the baby. Cesarean delivery results in tw

33、ice the average blood loss of vaginal delivery. Incisions in the poorly contractile lower segment heal well but are more reliant on suturing, vasospasm, and clotting for hemostasis. Uterine rupture is most common in patients with previous cesarean delivery scars. Routine transvaginal palpation of su

34、ch scars is no longer recommended. Any uterus that has undergone a procedure resulting in a total or thick partial disruption of the uterine wall should be considered at risk for rupture in a future pregnancy. This admonition includes fibroidectomy; uteroplasty for congenital abnormality; cornual or

35、 cervical ectopic resection; and perforation of the uterus during dilatation, curettage, biopsy, hysteroscopy, laparoscopy, or intrauterine contraceptive device placement.Trauma may occur following very prolonged or vigorous labor, especially if the patient has relative or absolute cephalopelvic dis

36、proportion and the uterus has been stimulated with oxytocin or prostaglandins. Using intrauterine pressure monitoring may lessen this risk. Trauma also may occur following extrauterine or intrauterine manipulation of the fetus. The highest risk is probably associated with internal version and extrac

37、tion of a second twin; however, uterine rupture may also occur secondary to external version. Finally, trauma may result secondary to attempts to remove a retained placenta manually or with instrumentation. The uterus should always be controlled with a hand on the abdomen during any such procedure.

38、An intraumbilical vein saline/oxytocin or saline/misoprostol injection may reduce the need for more invasive removal techniques.8 Cervical laceration is most commonly associated with forceps delivery, and the cervix should be inspected following all such deliveries. Assisted vaginal delivery (forcep

39、s or vacuum) should never be attempted without the cervix being fully dilated. Cervical laceration may occur spontaneously. In these cases, mothers have often been unable to resist bearing down before full cervical dilatation. Rarely, manual exploration or instrumentation of the uterus may result in

40、 cervical damage. Very rarely, the cervix is purposefully incised at the 2- and/or 10-oclock positions to facilitate delivery of an entrapped fetal head during a breech delivery (Dhrssen incision). Vaginal sidewall laceration is also most commonly associated with operative vaginal delivery, but it m

41、ay occur spontaneously, especially if a fetal hand presents with the head. Lacerations may occur during manipulations to resolve shoulder dystocia. Lacerations often occur in the region overlying the ischial spines. The frequency of sidewall and cervical lacerations has probably decreased in recent

42、years because of the reduction in the use of midpelvic forceps and, especially, midpelvic rotational procedures. Lower vaginal trauma occurs either spontaneously or because of episiotomy. Spontaneous lacerations usually involve the posterior fourchette; however, trauma to the periurethral and clitor

43、al region may occur and can be problematic.Thrombosis In the immediate postpartum period, disorders of the coagulation system and platelets do not usually result in excessive bleeding; this emphasizes the efficiency of uterine contraction and retraction for preventing hemorrhage.5 Fibrin deposition

44、over the placental site and clots within supplying vessels play a significant role in the hours and days following delivery, and abnormalities in these areas can lead to late PPH or exacerbate bleeding from other causes, most notably, trauma. Abnormalities may be preexistent or acquired. Thrombocyto

45、penia may be related to preexisting disease, such as idiopathic thrombocytopenic purpura, or acquired secondary to HELLP syndrome (hemolysis, elevated liver enzymes, and low platelet count), abruptio placentae, disseminated intravascular coagulation (DIC), or sepsis. Rarely, functional abnormalities

46、 of platelets may also occur. Most of these are preexisting, although sometimes previously undiagnosed. Preexisting abnormalities of the clotting system, such as familial hypofibrinogenemia and von Willebrand disease, may occur and should be considered. An expert panel recently issued guidelines to

47、aid in the diagnosis and management of women with such conditions.18 An underlying bleeding disorder should be considered in a woman with any of the following: menorrhagia since menarche, family history of bleeding disorders, personal history of notable bruising without known injury, bleeding from t

48、he oral cavity or GI tract without obvious lesion, or epistaxis of longer than 10 minutes duration (possibly requiring packing or cautery). If a bleeding disorder is suspected, consultation is suggested. Acquired abnormalities are more commonly problematic. DIC related to abruptio placentae, HELLP s

49、yndrome, intrauterine fetal demise, amniotic fluid embolism, and sepsis may occur. Fibrinogen levels are markedly elevated during pregnancy, and a fibrinogen level that would be in the reference range in the nonpregnant state should be viewed with suspicion in the aforementioned clinical scenarios.

50、Finally, dilutional coagulopathy may occur following massive PPH and resuscitation with crystalloid and packed red blood cells (PRBCs). Risk factors and associated conditions for PPH are listed above; however, a large number of women experiencing PPH have no risk factors. Different etiologies may ha

51、ve common risk factors, and this is especially true of uterine atony and trauma of the lower genital tract. PPH usually has a single cause, but more than one cause is also possible, most likely following a prolonged labor that ultimately ends in an operative vaginal birth.Prevention High-quality evi

52、dence suggests that active management of the third stage of labor reduces the incidence and severity of PPH.9 Active management is the combination of (1) uterotonic administration (preferably oxytocin) immediately upon delivery of the baby, (2) early cord clamping and cutting, and (3) gentle cord tr

53、action with uterine countertraction when the uterus is well contracted (ie, Brandt-Andrews maneuver). The value of active management in the prevention of PPH cannot be overstated (see Management of the Third Stage of Labor). The use of active versus expectant management in the third stage was the su

54、bject of 5 randomized controlled trials (RCTs) and a Cochrane meta-analysis.19, 8, 9 These trials included more than 6000 women, and the findings are summarized in Table 1.OutcomeControl Rate, %Relative Risk95% CI*NNT95% CIPPH of 500 mL140.380.32-0.461210-14PPH of 1000 mL2.60.330.21-0.515542-91Hemog

55、lobin 99%) are handled without what would traditionally be considered surgical intervention. In most cases, surgical intervention is a last resort. An exception is those cases in which uterine rupture or genital tract trauma has occurred and surgical repair is clearly indicated.Transfusion of packed

56、 RBC and other blood products may be necessary in the management of severe PPH. Some women may refuse such an intervention on personal or religious grounds. The most widely known group that does not accept blood transfusion are Jehovahs Witnesses. The wishes of the patient must be respected in this

57、matter. Significant increased risk of maternal mortality due to obstetric hemorrhage has been noted in the Jehovahs Witness population. The increased risk of death was found to be 6-fold in a recent national review of 23 years experience in the Netherlands and 44-fold in a much smaller study of 391

58、deliveries in a US tertiary level center.27, 28 Discussion regarding the implications of such prohibitions should be undertaken early in the pregnancy whenever possible and subsequently reviewed. In almost all cases in which surgical management is chosen after medical management has failed, not atte

59、mpting surgery would lead to maternal death. Even an unstable condition cannot be considered a true contraindication. One type of surgery may be chosen over another, but when medical management has failed, surgery is most likely the only life-saving option.Laboratory Studies In the antenatal period,

60、 a CBC is performed. Findings alert caregivers to women with anemia and indicate interventions to attempt to improve the hemoglobin level. Hemoglobin levels below 10-10.5 g/dL have been associated with adverse pregnancy outcome, and the rare patient with thrombocytopenia will be identified.29 Women