C1 esterase inhibitor activity in amniotic fluid embolism

Phenotypes of Disseminated Intravascular Coagulation

Two phenotypes of disseminated intravascular coagulation (DIC) are systematically reviewed. DIC is classified into thrombotic and fibrinolytic phenotypes characterized by thrombosis and hemorrhage, respectively. Major pathology of DIC with thrombotic phenotype is the activation of coagulation, insufficient anticoagulation with endothelial injury, and plasminogen activator inhibitor-1-mediated inhibition of fibrinolysis, leading to microvascular fibrin thrombosis and organ dysfunction. DIC with fibrinolytic phenotype is defined as massive thrombin generation commonly observed in any type of DIC, combined with systemic pathologic hyperfibrinogenolysis caused by underlying disorder that results in severe bleeding due to excessive plasmin formation. Three major pathomechanisms of systemic hyperfibrinogenolysis have been considered: (1) acceleration of tissue-type plasminogen activator (t-PA) release from hypoxic endothelial cells and t-PA-rich storage pools, (2) enhancement of the conversion of plasminogen to plasmin due to specific proteins and receptors that are expressed on cancer cells and endothelial cells, and (3) alternative pathways of fibrinolysis. DIC with fibrinolytic phenotype can be diagnosed by DIC diagnosis followed by the recognition of systemic pathologic hyperfibrin(ogen)olysis. Low fibrinogen levels, high fibrinogen and fibrin degradation products (FDPs), and the FDP/D-dimer ratio are important for the diagnosis of systemic pathologic hyperfibrin(ogen)olysis. Currently, evidence-based treatment strategies for DIC with fibrinolytic phenotypes are lacking. Tranexamic acid appears to be one of the few methods to be effective in the treatment of systemic pathologic hyperfibrin(ogen)olysis. International cooperation for the elucidation of pathomechanisms, establishment of diagnostic criteria, and treatment strategies for DIC with fibrinolytic phenotype are urgent issues in the field of thrombosis and hemostasis.

Comparative analysis of hyperfibrinolysis with activated coagulation between amniotic fluid embolism and severe placental abruption

Amniotic fluid embolism (AFE) and placental abruption (PA) are typical obstetric diseases associated with disseminated intravascular coagulation (DIC). AFE is more likely to be complicated with enhanced fibrinolysis than PA. AFE may have an additional mechanism activating fibrinolytic cascade. We aimed to compare the coagulation/fibrinolysis factors among AFE, PA, and peripartum controls. We assessed AFE cases registered in the Japanese AFE Registry, and PA cases complicated with DIC (severe PA) and peripartum controls recruited at our hospital. The following factors in plasma were compared: prothrombin fragment 1 + 2 (PF1 + 2), plasmin α2-plasmin inhibitor complex (PIC), tissue factor (TF), tissue plasminogen activator (tPA), annexin A2 (AnnA2), total thrombin activatable fibrinolysis inhibitor (TAFI) including its activated form (TAFIa), and plasminogen activator inhibitor-type 1 (PAI-1). PF1 + 2 and PIC were markedly increased in both AFE (n = 27) and severe PA (n = 12) compared to controls (n = 23), without significant difference between those disease groups; however, PIC in AFE showed a tendency to elevate relative to PF1 + 2, compared with severe PA. AFE had significantly increased tPA and decreased total TAFI levels compared with severe PA and controls, which might be associated with further plasmin production in AFE and underlie its specific fibrinolytic activation pathway.

Pulmonary Embolism and Amniotic Fluid Embolism

Venous thromboembolism (VTE) as well as other embolic events including amniotic fluid embolism (AFE) remain a leading cause of maternal death in the United States and worldwide. The pregnant patient is at a higher risk of developing VTE including pulmonary embolism. In contrast, AFE is a rare, but catastrophic event that remains incompletely understood. Here the authors review the cause of VTE in pregnancy and look at contemporary and evidence-based practices for the evaluation, diagnosis, and management in pregnancy. Then the cause and diagnostic difficulty of AFE as well as what is known regarding the pathogenesis are reviewed.

Early Diagnosis of the Cardiopulmonary Collapse Type of Amniotic Fluid Embolism with Obstetrical Disseminated Intravascular Coagulation during Elective Cesarean Section : A Case Report

Two types of amniotic fluid embolism (AFE) have been described : cardiopulmonary collapse type and disseminated intravascular coagulation (DIC) type, with the latter proposed as uterine type. This report describes a healthy 28-year-old woman who developed AFE during a cesarean section. Because of a previous cesarean section, the patient underwent an elective cesarean section, under combined spinal-epidural anesthesia, at 38 weeks of pregnancy. She began coughing 5 minutes after delivery of the fetus, subsequently becoming unconscious and developing glossoptosis and bradycardia. Her blood pressure decreased to 76/43 mmHg, and AFE was suspected. Her uterus was atonic, and she experienced persistent noncoagulant bleeding, with a final blood loss of 6300 ml. Considerable blood transfusion was required. The patient survived, and she and her baby were discharged without any sequelae on the eighth postoperative day. This patient met the Japanese criteria for clinical AFE, with an obstetrical DIC score of 21 meeting the criteria for obstetrical DIC. Early diagnosis and treatment likely resulted in patient survival. J. Med. Invest. 67 : 207-210, February, 2020.

Consumptive Coagulopathy Involving Amniotic Fluid Embolism: The Importance of Earlier Assessments for Interventions in Critical Care

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Objectives:

Amniotic fluid embolism is a rare disease that induces fatal coagulopathy; however, due to its rarity, it has not yet been examined in detail. The strict diagnostic criteria by Clark for amniotic fluid embolism include severe coagulopathy complicated by cardiopulmonary insufficiency, whereas the Japanese criteria also include postpartum hemorrhage or Disseminated Intravascular Coagulation in clinical practice. Amniotic fluid embolism cases with preceding consumptive coagulopathy may exist and are potential clinical targets for earlier assessments and interventions among amniotic fluid embolism cases fulfilling the Japanese, but not Clark criteria. The present study was performed to compare coagulopathy in the earlier stage between the amniotic fluid embolism patients diagnosed by Clark criteria (Clark group, n = 6), those by the Japanese criteria (Non-Clark group, n = 10), and peripartum controls and identify optimal clinical markers for earlier assessments of amniotic fluid embolism-related consumptive coagulopathy.

Design:

Retrospective case-control study.

Setting:

A single university-based center. Our amniotic fluid embolism registry program has accumulated clinical information and blood samples since 2003.

Patients:

Amniotic fluid embolism patients in the Clark and Non-Clark groups between 2009 and 2017 and peripartum controls.

Interventions:

None.

Measurements and Main Results:

Clinical information was collected on hemoglobin levels, platelet counts, and coagulation- and fibrinolysis-related variables. Fibrinolytic parameters were also measured and compared among the three groups before blood transfusion. Fibrinogen levels in all patients in the Clark group and most in the Non-Clark group decreased earlier than hemoglobin levels, which was consistent with the high hemoglobin/fibrinogen ratio and, thus, is a promising clinical marker for the earlier assessment of amniotic fluid embolism-related consumptive coagulopathy.

Conclusions:

Earlier evaluations of consumptive coagulopathy and hyperfibrinolysis using the hemoglobin/fibrinogen ratio following preemptive treatment may reduce the occurrence or prevent the aggravation of severe coagulopathy in amniotic fluid embolism patients.

Disseminated intravascular coagulation type of amniotic fluid embolism: a challenging case report with favorable outcome

Amniotic fluid embolism (AFE) is an unforeseeable, life-threatening complication of pregnancy and child birth. Although rare in an absolute sense, most contemporary series of maternal deaths from developed countries report AFE as a leading cause of mortality in the pregnant population. It has a heterogeneous presentation. This clinical heterogeneity makes the diagnosis of AFE difficult based on a beam of clinical and para-clinical arguments. Rapid diagnosis and immediate interdisciplinary treatment are essential for a good outcome. The present is a case of AFE with a disseminated intravascular coagulation (DIC) and a cardiorespiratory collapse following a vaginal delivery.

Biochemical effects of intraoperative cell salvage and autotransfusion during cesarean section: A prospective pilot study

AIM

Intraoperative cell salvage and autotransfusion (ICSA) is a useful technique for women undergoing cesarean sections who are predicted to experience significant bleeding. This method can reduce allogeneic transfusions as well as its associated risks and costs. Amniotic fluid embolism (AFE) is an abnormal maternal response to ICSA similar to the classic systemic inflammatory response syndrome, but its mechanism is not well understood. This study was conducted to investigate the biochemical aspects of AFE.

METHODS

A prospective case-controlled pilot study was conducted in a general perinatal hospital in Japan. ICSA was performed using a two-step retransfusion process. Blood samples were collected presurgery, immediately postsurgery, and 24 h after surgery. Changes in sialyl Tn antigen (STN), complement C3 and C4, fibrinogen, and fibrin degradation product and D-dimer, C1 esterase inhibitor, and interleukin-8 (all considered AFE-related markers) activities were compared between patients who underwent cesarean sections with ICSA (ICSA group) versus without ICSA (control group).

RESULTS

Fibrinogen levels were significantly lower in the ICSA group than in the control group before surgery but not immediately after or 24 h after surgery. D-dimer was significantly higher immediately after surgery but not 24 h later. STN was significantly lower only before surgery. None of the AFE-related markers showed significant differences between the groups after 24 h. No adverse events were observed in the ICSA group.

CONCLUSIONS

There is no clinical evidence that ICSA alters the biochemical statuses of AFE-related markers in a manner that could lead to adverse maternal responses.

Reference range for C1-esterase inhibitor (C1 INH) in the third trimester of pregnancy

OBJECTIVES

The objectives of this study were to (i) establish the reference range and mean value for normal levels of C1-esterase inhibitor (C1 INH) during pregnancy, and (ii) investigate the association between C1 INH and uterine atony, as measured by blood loss at delivery.

METHODS

We prospectively studied 200 healthy pregnant women who were registered. We studied C1 INH levels in 188 women at 34 and 35 gestational weeks of pregnancy. The reference range for C1 INH during the third trimester of pregnancy was calculated using the value of C1 INH that was determined at registration.

RESULTS

The mean value of C1 INH was determined to be 70.3% (95% confidence interval, 68.7-71.9). While the C1 INH levels in four women were determined to be 40% lower than the calculated mean value, amniotic fluid embolism (AFE) did not occur in any of the women studied.

CONCLUSIONS

This study successfully demonstrated that a reference value for C1 INH activity can be established using the methods described herein. Further research is needed to determine whether C1 INH is involved in obstetric coagulopathy syndrome such as amniotic fluid embolism.

Acute inflammation in the uterine isthmus coincides with postpartum acute myometritis in the uterine body involving refractory postpartum hemorrhage of unknown etiology after cesarean delivery

Uterine atony is a major cause of postpartum hemorrhage. We recently proposed the new histological concept of postpartum acute myometritis (PAM) for the pathophysiology of refractory uterine atony of unknown etiology, which is characterized by the diffuse activation of mast cells and the complement system as well as the massive infiltration of macrophages and neutrophils into the uterine body. We herein focused on the uterine isthmus just adjacent to the body. The isthmus becomes significantly elongated throughout pregnancy. It is composed of myocytes and fibroblasts with an extracellular matrix that forms a passive lower segment during labor. The aim of this study was to histologically examine the uterine isthmus in cases of PAM in the uterine body. Under the amniotic fluid embolism-registry program in Japan, we selected PAM cases from uterine samples obtained by cesarean hysterectomy and delivered to us for analyses between 2011 and 2017. Control tissues were collected during elective cesarean section. We investigated the isthmus tissues of these cases and performed immunohistochemistry for inflammatory cell markers, i.e. neutrophil elastase, mast cell tryptase, CD68, CD3, and C5a receptor (C5aR). The numbers of tryptase-positive degranulating mast cells, elastase-positive neutrophils, CD68-positive macrophages, and C5aR-positive cells in the isthmus were significantly higher in uteri with PAM in the body than in controls without PAM. CD3 was negative in both groups. In conclusion, inflammation and an anaphylactoid reaction were histologically detected not only in the uterine body, but in the isthmus among cases of refractory PPH of unknown etiology after cesarean section.

A case of amniotic fluid embolism successfully treated by multidisciplinary treatment

Background

Amniotic fluid embolism (AFE) is a life-threatening obstetric emergency. Because the maternal mortality associated with AFE is very high, early recognition and prompt treatment are important for improving the prognosis. We report a case of amniotic fluid embolism successfully treated by multidisciplinary treatment.

Case presentation

A 39-year-old woman with fetal congenital heart anomaly and polyhydramnios was scheduled for induction of delivery at 37 weeks of gestation with labor epidural analgesia. Uncontrollable bleeding occurred 30 min after vaginal delivery. Based on the clinical diagnosis of AFE, massive blood transfusion, insertion of an aortic occlusion balloon catheter, and hysterectomy was performed. Total blood loss was 12,000 mL. The diagnosis of AFE was confirmed by pathological examination. She was discharged with no complications.

Conclusion

We report a case of AFE who were rescued by prompt diagnosis and treatment.

Practical use of C1 esterase inhibitor concentrate for clinical amniotic fluid embolism

Amniotic fluid embolism (AFE) causes consumption coagulopathy, which requires a massive transfusion to save the mother's life. The preparation of such a massive transfusion is too time-consuming in extremely emergent clinical settings and occasionally leads to devastating side effects such as transfusion-associated acute lung injury. C1 esterase inhibitor (C1INH) is a protein with the ability to inhibit complement, coagulation and kinin pathways. The C1INH concentration in AFE patients is low, and it has been speculated that the administration of C1INH concentrate could have a striking and beneficial effect on AFE patients in critical condition by ameliorating their perturbed coagulation system. We report the case of a 32-year-old Japanese AFE patient in whom deteriorated vital signs and coagulopathy recovered within minutes after an injection of C1INH concentrate. C1INH concentrate can quickly revive the deteriorated vital signs and the atonic uterus that stem from AFE and may reduce the total amount of transfusion.

Amniotic fluid embolism mortality rate

AIM

The objective of this study was to determine the mortality rate of amniotic fluid embolism (AFE) using population-based studies and case series.

METHODS

A literature search was conducted using the two key words: 'amniotic fluid embolism (AFE)' AND 'mortality rate'. Thirteen population-based studies were evaluated, as well as 36 case series including at least two patients.

RESULTS

The mortality rate from population-based studies varied from 11% to 44%. When nine population-based studies with over 17 000 000 live births were aggregated, the maternal mortality rate was 20.4%. In contrast, the mortality rate of AFE in case series varies from 0% to 100% with numerous rates in between.

CONCLUSION

The AFE mortality rate in population-based studies varied from 11% to 44% with the best available evidence supporting an overall mortality rate of 20.4%. Data from case series should no longer be used as a basis for describing the lethality of AFE.

Efficacy of transfusion with fresh-frozen plasma:red blood cell concentrate ratio of 1 or more for amniotic fluid embolism with coagulopathy: a case-control study

BACKGROUND

The Japan Association of Obstetricians and Gynecologists (JAOG) recommends transfusion with a fresh-frozen plasma (FFP):red blood cell (RBC) ratio of 1 or more in postpartum hemorrhage. However, no global consensus exists concerning this, and little is known regarding the impact of FFP:RBC ratio on maternal mortality. This study evaluates the efficacy of transfusion with FFP:RBC ratio of 1 or more for amniotic fluid embolism (AFE) with coagulopathy.

STUDY DESIGN AND METHODS

The Maternal Death Exploratory Committee, established by the JAOG, conducted this retrospective nationwide case-control study in Japan. Women with AFE and coagulopathy were included in the study and were stratified into survival and death groups. Obstetric variables and therapy methods (hysterectomy, uterine artery embolism, and transfusion with FFP:RBC ratio ≥ 1) were compared between the survival and death groups.

RESULTS

A total of 54 women had AFE and coagulopathy (death group, n = 22; survival group, n = 32). Only nine (40.9%) women in the death group were transfused with FFP:RBC ratio of 1 or more, whereas 29 (90.6%) women in the survival group were transfused with FFP:RBC ratio of 1 or more. FFP:RBC ratio of 1 or more was found to be associated with better survival rate (adjusted odds ratio, 28.32; 95% confidence interval, 4.26-188.37). No difference was found in obstetric variables, hysterectomy, and uterine artery embolism between survival and death groups.

CONCLUSION

Transfusion with FFP:RBC ratio of 1 or more is associated with higher survival rate in women with AFE with coagulopathy.

Egg serpins: The chicken and/or the egg dilemma

Twenty-seven serpins belonging to clade A, B, C, D, E, F, G, H and I serpins are currently referenced in chicken genome databases. Phylogenetic analysis of chicken serpins revealed that ovalbumin (Serpinb14) and its paralogs ovalbumin-related protein Y (Serpinb14b) and ovalbumin-related protein X (Serpinb14c) are found in bird species. These clade B serpins are specifically expressed in reproductive tissues and exported in the egg where they constitute major protein components. These data suggest that these three paralogs have probably appeared in birds to face new environments and ensure the extra-uterine development of an embryo in a shell egg. Twelve other serpins have been identified in the newly produced egg, some of them having a specific distribution in the respective egg structures (eggshell, egg white, vitelline membrane and egg yolk). The physiological role of these egg serpins remain largely unexplored, but there is increasing evidence in literature or by homologies with their mammalian counterparts, that some of them participate in cell proliferation, tissue remodeling and/or angiogenesis associated with folliculogenesis and development of extraembryonic structures, eggshell biomineralization, egg defense and nutrition of the embryo. A better knowledge of the phylogenetic evolution of these 15 serpins in other oviparous species, on their egg distribution, on their regulation during embryonic development (activation/degradation/transfer) and on their functional specificity, is needed to better appreciate their role and their bird-specificity. These review shed light on the multiple possibilities that offer the avian egg model to study the role of serpins in reproduction and developmental biology.

Acute respiratory failure in pregnancy

Respiratory failure affects up to 0.2% of pregnancies, more commonly in the postpartum period. Altered maternal respiratory physiology affects the assessment and management of these patients. Respiratory failure may result from pregnancy-specific conditions such as preeclampsia, amniotic fluid embolism or peripartum cardiomyopathy. Pregnancy may increase the risk or severity of other conditions, including thromboembolism, asthma, viral pneumonitis, and gastric acid aspiration. Management during pregnancy is similar to the nonpregnant patient. Endotracheal intubation in pregnancy carries an increased risk, due to airway edema and rapid oxygen desaturation following apnea. Few data are available to direct prolonged mechanical ventilation in pregnancy. Chest wall compliance is reduced, perhaps permitting slightly higher airway pressures. Optimizing oxygenation is important, but data on the use of permissive hypercapnia are limited. Delivery of the fetus does not always improve maternal respiratory function, but should be considered if benefit to the fetus is anticipated.

Therapeutic application of C1 esterase inhibitor concentrate for clinical amniotic fluid embolism: a case report

We present the successful application of C1 esterase inhibitor (C1INH) concentrate to a patient with clinical amniotic fluid embolism (AFE).

Histological characteristics of the myometrium in the postpartum hemorrhage of unknown etiology: a possible involvement of local immune reactions

The aim of this study was to evaluate the histological characteristics of the myometrium obtained in postpartum hemorrhage (PPH) of unknown etiology secondary to uterine atony. These characteristics were selected from among registered cases of clinically suspected amniotic fluid embolism (AFE) and classified as PPH of unknown etiology because of no obvious cause of PPH at Hamamatsu University School of Medicine, a registration center for clinical AFE in Japan. Immunohistochemical studies were performed on myometrium using anti-mast cell tryptase, anti-neutrophil elastase, anti-CD68, anti-CD88, anti-CD3, and anti-ZnCP-1 antibodies. Massive infiltrations of inflammatory cells with mast cell degranulation within the myometrium secondary to complement activation were observed in PPH of unknown etiology (n=34), but not in control pregnant women (n=15) or after delivery in women without PPH (n=18). The concomitant immunohistochemical detection of meconium in myometrium suggests that amniotic fluids or fetal materials are one of the candidates for inducing maternal local immune activation in the PPH of unknown etiology. Postpartum acute myometritis in the absence of an infective etiology may be a histological characteristic of PPH of unknown etiology.

Amniotic fluid embolism pathophysiology suggests the new diagnostic armamentarium: β-tryptase and complement fractions C3-C4 are the indispensable working tools

Amniotic fluid embolism (AFE) is an uncommon obstetric condition involving pregnant women during labor or in the initial stages after delivery. Its incidence is estimated to be around 5.5 cases per 100,000 deliveries. Therefore, this paper investigated the pathophysiological mechanism, which underlies AFE, in order to evaluate the role of immune response in the development of this still enigmatic clinical entity. The following databases (from 1956 to September 2014) Medline, Cochrane Central, Scopus, Web of Science and Science Direct were used, searching the following key words: AFE, pathophysiology, immune/inflammatory response, complement and anaphylaxis. The main key word “AFE” was searched singularly and associated individually to each of the other keywords. Of the 146 sources found, only 19 were considered appropriate for the purpose of this paper. The clinical course is characterized by a rapid onset of symptoms, which include: acute hypotension and/or cardiac arrest, acute hypoxia (with dyspnoea, cyanosis and/or respiratory arrest), coagulopathies (disseminated intravascular coagulation and/or severe hemorrhage), coma and seizures. The pathology still determines a significant morbidity and mortality and potential permanent neurological sequelae for surviving patients. At this moment, numerous aspects involving the pathophysiology and clinical development are still not understood and several hypotheses have been formulated, in particular the possible role of anaphylaxis and complement. Moreover, the detection of serum tryptase and complement components and the evaluation of fetal antigens can explain several aspects of immune response.

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Successful resuscitation of amniotic fluid embolism applying a new classification and management strategy

Amniotic fluid embolism (AFE) is a rare but life-threatening maternal emergency caused by the entry of amniotic fluid contents into the maternal circulation. The clinical manifestations of AFE are heterogeneous, leading to misdiagnosis or treatment delay. Kanayama and colleagues distinguished the cardiopulmonary collapse type (or classic type) from the disseminated intravascular coagulation (DIC) type of AFE on the basis of the presence of uterine atony and DIC in the latter prior to cardiopulmonary failure. We report a case of DIC-type AFE successfully treated by blood volume replacement and coagulation therapy. The patient was scheduled for elective cesarean delivery because of a previous cesarean section and moyamoya disease. Delivery was uneventful, but massive vaginal bleeding without clotting and ensuing hypovolemic shock occurred 4 h later. She was transferred to the operating room for emergency laparotomy, but sustained a cardiac arrest. The patient was successfully resuscitated and a hysterectomy performed. During surgery, the patient received fresh frozen plasma, platelets, fibrinogen, and antithrombin concentrate. In cardiopulmonary collapse type AFE, cardiopulmonary resuscitation without delay is important. In the present case of DIC-type AFE, however, early supplementation of clotting factors and platelets was critical for patient survival.