Pulmonary vascular obstruction by squamous cells is not involved in amniotic fluid embolism

Histological differences among thrombi in thrombotic diseases

PURPOSE OF REVIEW

This review aims to summarize the histological differences among thrombi in acute myocardial infarction, ischemic stroke, venous thromboembolism, and amniotic fluid embolism, a newly identified thrombosis.

RECENT FINDINGS

Acute coronary thrombi have a small size, are enriched in platelets and fibrin, and show the presence of fibrin and von Willebrand factor, but not collagen, at plaque rupture sites. Symptomatic deep vein thrombi are large and exhibit various phases of time-dependent histological changes. Cancer-associated venous thromboemboli contain invasive cancer cells that penetrate the vascular walls, and small cancer cell aggregates are observed within the thrombi. The thrombus composition in atherosclerotic and cardioembolic ischemic strokes varies from case to case, while the thrombi in cancer-associated ischemic stroke are rich in platelets and fibrin. A pathological study on amniotic fluid embolism identified uterine vein thrombi and massive platelet-rich microthrombi in the lungs.

SUMMARY

Atherothrombus formation is induced by plaque disruption and may occlude a narrow lumen within a short time. Venous thrombi may grow to a large size in a multistage or chronic manner. Cancer cells can directly contribute to venous thrombus formation. The thrombus formation in amniotic fluid embolism may explain the occurrence of consumptive coagulopathy and cardiopulmonary collapse.

Extracorporeal Membrane Oxygenation in Amniotic Fluid Embolism: A Systematic Review of Case Reports

Amniotic fluid embolism (AFE) is an obstetric complication that can result in acute circulatory failure during and after labor. The effectiveness of extracorporeal membrane oxygenation (ECMO) in AFE patients has not been established, especially in the context of coagulopathy. This review aims to evaluate the efficacy of ECMO support in AFE patients. We conducted a systematic review of case reports following the Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Quality assessment was performed using a standardized tool. Out of 141 studies screened, 33 studies included 79 AFE patients. The median age was 34 years, and the median gestational age was 37.5 weeks. The majority of AFE cases occurred during cesarean section delivery (55.2%), followed by labor before fetal delivery (26.7%). Extracorporeal membrane oxygenation configurations included venoarterial ECMO (81.3%) and extracorporeal cardiopulmonary resuscitation (CPR, 10.7%). The maternal survival rate was 72%, with 21.2% experiencing minor neurological sequelae and 5.8% having major neurological sequelae. Rescue ECMO to support circulation has demonstrated both safety and efficacy in managing AFE. We suggest early activation of local or mobile ECMO as soon as an AFE diagnosis is established. Further studies are needed to assess the benefits and implications of early ECMO support in AFE patients.

Massive platelet-rich thrombus formation in small pulmonary vessels in amniotic fluid embolism: An autopsy study

OBJECTIVE

To identify pulmonary/uterine thrombus formation in amniotic fluid embolism (AFE).

DESIGN

Retrospective, observational.

SETTING

Nationwide.

POPULATION

Eleven autopsy cases of AFE and control cases.

METHODS

We assessed pulmonary and uterine thrombus formation and thrombus area in AFE and pulmonary thromboembolism (PTE) as a control. The area of platelet glycoprotein IIb/IIIa, fibrin, neutrophil elastase, citrullinated histone H3 (a neutrophil extracellular trap marker) and mast cell chymase immunopositivity was measured in 90 pulmonary emboli, 15 uterine thrombi and 14 PTE.

MAIN OUTCOME MEASURES

Pathological evidence of thrombus formation and its components in AFE.

RESULTS

Amniotic fluid embolism lung showed massive thrombus formation, with or without amniotic emboli in small pulmonary arteries and capillaries. The median pulmonary thrombus size in AFE (median, 0.012 mm2 ; P < 0.0001) was significantly smaller than that of uterine thrombus in AFE (0.61 mm2 ) or PTE (29 mm2 ). The median area of glycoprotein IIb/IIIa immunopositivity in pulmonary thrombi in AFE (39%; P < 0.01) was significantly larger than that of uterine thrombi in AFE (23%) and PTE (15%). The median area of fibrin (0%; P < 0.001) and citrullinated histone H3 (0%; P < 0.01) immunopositivity in pulmonary thrombi in AFE was significantly smaller than in uterine thrombi (fibrin: 26%; citrullinated histone H3: 1.1%) and PTE (fibrin: 42%; citrullinated histone H3: 0.4%). No mast cells were identified in pulmonary thrombi.

CONCLUSIONS

Amniotic fluid may induce distinct thrombus formation in the uterus and lung. Pulmonary and uterine thrombi formation may contribute to cardiorespiratory collapse and/or consumptive coagulopathy in AFE.

McConnell's Sign in a Patient with Amniotic Fluid Embolism and Severe Right Ventricular Dysfunction

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McConnell’s sign may be an early sign of acute RV strain in amniotic fluid embolus.

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TTE could be considered to facilitate timely diagnosis of amniotic fluid embolus.

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The presence of RV dysfunction on TTE may help guide hemodynamic therapies.

Society for Maternal-Fetal Medicine Special Statement: Checklist for initial management of amniotic fluid embolism

Amniotic fluid embolism is a rare syndrome characterized by sudden cardiorespiratory collapse during labor or soon after delivery. Because of its rarity, many obstetrical providers have no experience in managing amniotic fluid embolism and may therefore benefit from a cognitive aid such as a checklist. We present a sample checklist for the initial management of amniotic fluid embolism based on standard management guidelines. We also suggest steps that each facility can take to implement the checklist effectively.

Amniotic fluid embolism syndrome: analysis of the Unites States International Registry

BACKGROUND

Incidence, risk factors, and perinatal morbidity and mortality rates related to amniotic fluid embolism remain a challenge to evaluate, given the presence of differing international diagnostic criteria, the lack of a gold standard diagnostic test, and a significant overlap with other causes of obstetric morbidity and mortality.

OBJECTIVE

The aims of this study were (1) to analyze the clinical features and outcomes of women using the largest United States-based contemporary international amniotic fluid embolism registry, and (2) to investigate differences in demographic and obstetric variables, clinical presentation, and outcomes between women with typical versus atypical amniotic fluid embolism, using previously published and validated criteria for the research reporting of amniotic fluid embolism.

MATERIALS AND METHODS

The AFE Registry is an international database established at Baylor College of Medicine (Houston, TX) in partnership with the Amniotic Fluid Embolism Foundation (Vista, CA) and the Perinatology Research Branch of the Division of Intramural Research of the NICHD/NIH/DHHS (Detroit, MI). Charts submitted to the registry between August 2013 and September 2017 were reviewed, and cases were categorized into typical, atypical, non-amniotic fluid embolism, and indeterminate, using the previously published and validated criteria for the research reporting of AFE. Demographic and clinical variables, as well as outcomes for patients with typical and atypical AFE, were recorded and compared. Student t tests, χ2 tests, and analysis of variance tables were used to compare the groups, as appropriate, using SAS/STAT software, version 9.4.

RESULTS

A total of 129 charts were available for review. Of these, 46% (59/129) represented typical amniotic fluid embolism and 12% (15/129) atypical amniotic fluid embolism, 21% (27/129) were non-amniotic fluid embolism cases with a clear alternative diagnosis, and 22% (28/129) had an uncertain diagnosis. Of the 27 women misclassified as an amniotic fluid embolism with an alternative diagnosis, the most common actual diagnosis was hypovolemic shock secondary to postpartum hemorrhage. Ten percent (6/59) of the women with typical amniotic fluid embolism had a pregnancy complicated by placenta previa, and 8% (5/61) had undergone in vitro fertilization to achieve pregnancy. In all, 66% (49/74) of the women with amniotic fluid embolism reported a history of atopy or latex, medication, or food allergy, compared to 34% of the obstetric population delivered at our hospital over the study period (P < .05).

CONCLUSION

Our data represent a series of women with amniotic fluid embolism whose diagnosis has been validated by detailed chart review, using recently published and validated criteria for research reporting of amniotic fluid embolism. Although no definitive risk factors were identified, a high rate of placenta previa, reported allergy, and conceptions achieved through in vitro fertilization was observed.

Extracorporeal Therapies for Amniotic Fluid Embolism

BACKGROUND

Amniotic fluid embolism (AFE) is a catastrophic disease with significant mortality. Because the cardiopulmonary dysfunction associated with AFE is self-limited, the disease could be well suited to the use of extracorporeal therapies.

CASE

A woman progressed into cardiac arrest immediately after an elective cesarean delivery. Owing to severe hypoxemia and hypotension, AFE was suspected and peripheral venoarterial extracorporeal membrane oxygenation was quickly initiated. Subsequent evolution was complicated by intrabdominal bleeding, which required massive transfusion and multiple surgeries. The patient recovered well, with a healthy newborn. We have identified 19 similar cases in the literature and present their outcomes as a series.

CONCLUSION

Extracorporeal therapies can support severely ill women affected by AFE and could be considered even in the presence of disseminated intravascular coagulation and bleeding.