Incidence, diagnosis and pathophysiology of amniotic fluid embolism

Echocardiography findings in amniotic fluid embolism: a systematic review of the literature

PURPOSE

Amniotic fluid embolism (AFE) is a leading cause of obstetrical cardiac arrest and maternal morbidity. The pathogenesis of hemodynamic collapse is thought to be from right ventricular (RV) failure; however, there is a paucity of data documenting echocardiography findings in this population. We undertook a systematic review of the literature to evaluate the echocardiography findings in patients with AFE.

SOURCES

We retrieved all case reports and case series reporting AFE in Embase and MEDLINE from inception to 20 November 2021. Studies reporting AFE diagnosed by fulfilling at least one of three different proposed AFE criteria and echocardiography findings during hospitalization were included. Patient and echocardiographic data were retrieved, and univariate logistic regression analysis was performed for outcomes of interest. Bias was assessed using the Joanna Briggs Institute clinical appraisal tool for case series.

PRINCIPAL FINDINGS

Eighty publications reporting on 84 patients were included in the final review. Fifty-five out of 82 patients with data (67%) showed RV dysfunction, including 11/82 (13%) with biventricular dysfunction; 14/82 (17%) had normal systolic function. No data on RV or left ventricular function were reported for two patients. The presence of RV dysfunction on echocardiography was associated with cardiac arrest (odds ratio [OR], 3.66; 95% confidence interval [CI], 1.39 to 9.67; P = 0.009), and a composite risk of cardiac arrest, maternal death or use of extracorporeal membrane oxygenation (OR, 3.86; 95% CI, 1.43 to 10.4; P = 0.007). A low risk of bias was observed in 15/84 (18%) cases.

CONCLUSIONS

Right ventricular dysfunction on echocardiography is a common finding in AFE and is associated with a high risk of cardiac arrest. The finding of RV dysfunction on echocardiography may help diagnose AFE and help triage the highest risk patients with AFE.

STUDY REGISTRATION

PROSPERO (CRD42021271323); registered 1 September 2021.

Neuroimaging and radiation exposure in pregnancy

Physiologic changes occurring in pregnancy and postpartum can have secondary effects on the maternal nervous system. While most alterations to neurologic function during pregnancy are transient, there is an elevated risk for more serious complication in the peripartum period, such as cerebrovascular events or exacerbation of preexisting neurologic conditions. Due to the morbidity and mortality associated with these neurologic manifestations in some cases, timely diagnostic evaluation is essential. In the pregnant population, the use of diagnostic techniques such as computed tomography (CT) and magnetic resonance imaging (MRI), commonly employed to evaluate emergent neurologic abnormalities, requires special consideration of the potential risks associated with prenatal exposure. This review discusses several neurologic conditions affecting women during pregnancy for which diagnostic imaging may be warranted. Concerns relating to CT and MRI procedures, radiation exposure in utero, and exposure to intravenous contrast by placental transfer and breastfeeding are also reviewed.

Efficiency of leukocyte depletion filters and micro-aggregate filters following intra-operative cell salvage during cesarean delivery

BACKGROUND

Intra-operative cell salvage is not routinely used during cesarean delivery because it is not cost-effective for patients at low risk of hemorrhage and there are theoretical concerns about amniotic fluid embolism. Some guidelines recommend using leukocyte depletion filters to decrease the risk of amniotic fluid embolism before re-infusing salvaged blood, but these filters are not available in Japan. We compared the efficacy and safety of leukocyte depletion and micro-aggregate filters in combination with intra-operative cell salvage during cesarean delivery.

METHODS

Blood was collected in a Cell Saver 5 reservoir during cesarean delivery. Four samples were collected: pre-wash, post-wash, post-filtration with a leukocyte depletion filter and post-filtration with a micro-aggregate filter. Each sample was analyzed for amniotic fluid markers of zinc coproporphyrin-1 and sialyl-Tn, for fetal hemoglobin, and the sample underwent pathological examination for white blood cells and squamous cells. Post-filtration samples were compared using paired t-tests with P <0.05 indicating statistical significance.

RESULTS

Zinc coproporphyrin-1 and sialyl-Tn were negative at almost all sample points. Squamous cells decreased by 59.1% post-wash and 91.2% post-filtration using a leukocyte depletion filter. Leukocyte depletion filters removed 99.7% of white blood cells and were more effective in removing white blood cells than micro-aggregate filters (P=0.02).

CONCLUSION

Leucocyte depletion filters are more effective in removing white blood cells and squamous cells than micro-aggregate filters, and their introduction for intra-operative cell salvage during cesarean delivery should be considered in Japanese clinical practice.

Clinical Presentation and Treatment of Amniotic Fluid Embolism

Obstetric emergencies often require intensive care intervention. Amniotic fluid embolism is a rare, unpredictable, and often catastrophic complication of pregnancy that is suspected in a woman who experiences cardiac arrest after a cesarean section. The condition occurs in approximately 1 in 40 000 births and has an average case-fatality rate of 16%. This complication may result from activation of an inflammatory response to fetal tissue in the maternal circulation. Risk factors may include maternal age over 35 years and conditions in which fluid can exchange between the maternal and fetal circulations. The presentation is abrupt, with profound cardiovascular and respiratory compromise, encephalopathy, fetal distress, and disseminated intravascular coagulopathy. Diagnosis is by exclusion and clinical presentation. Treatment is supportive, with a focus on reversal of hypoxia and hypotension, delivery of the fetus, and correction of coagulopathy. Staff debriefing and psychological support for the woman and family are vital.

Beyond Pulmonary Embolism; Nonthrombotic Pulmonary Embolism as Diagnostic Challenges

Nonthrombotic pulmonary embolism (NTPE) is less well understood and is encountered less frequently than pulmonary embolism from venous thrombosis. NTPE results from embolization of nonthrombotic material to the pulmonary vasculature originating from many different cell types as well as nonbiologic or foreign materials. For many radiologists NTPE is a challenging diagnosis, presenting nonspecific or unusual imaging findings in the setting of few or unusual clinical signs. The aim of this paper is to review the pathophysiology of diverse causes of NTPE, which should aid radiologists to better understand and, more importantly, diagnose these infrequent events.

Comparison of the Different Definition Criteria for the Diagnosis of Amniotic Fluid Embolism

INTRODUCTION

There are several sets of criteria for the diagnosis of Amniotic Fluid Embolism (AFE), but little is known about their degree of agreement.

AIM

To evaluate the concordance of the Japan criteria for AFE in comparison with two definitions: the US AFE registration entry criteria (the US criteria) and UK Obstetric Surveillance System criteria for defining cases of amniotic fluid embolism (the UK criteria).

MATERIALS AND METHODS

A retrospective observational study was conducted in which the AFE cases registered in the Obstetrical Gynaecological Society of Kinki District in Japan for the period of April 2005 to December 2012 have been analysed by the expert steering obstetric committee, organized by the members of the Obstetric Research group. Cohen's kappa coefficient was used to calculate the agreement among three clinical diagnoses. For inter-group comparison, the Pearson Chi-square test was used (for categorical) and Mann-Whitney test was used (for continuous variables).

RESULTS

Among the 26 cases registered for this period, a total of 18 women were selected as having AFE according to the Japan criteria. Five women died (case fatality rate 27.8%). Agreement between the Japan criteria and the US and UK criteria was k = 0.453 and k = 0.538, respectively, reflecting moderate agreement. However, only 38.9% were given a diagnosis of AFE according to all three criteria. The factor that most often caused disagreement in diagnosis between the Japan criteria and the US criteria was "onset within 30 minutes postpartum". The UK criteria excluded "women with postpartum haemorrhage as the first presenting feature in whom there was no evidence of cardiorespiratory compromise". The case fatality rates in US and UK are higher than in Japan (50.0% and 38.5% vs 27.8%), but this did not result in a significant difference (p=0.497).

CONCLUSION

The groups of subjects identified as having AFE by the Japan criteria had a medium agreement with the US (k=0.453) or UK criteria (k=0.538). These three definition criteria identified different subgroups of patients. Such disagreement has serious implications for research and treatment.

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.

Pulmonary embolism in the setting of HELLP syndrome

HELLP syndrome (hemolysis, elevated liver enzymes and low platelets) complicates 0.5-0.9% of pregnancies and is frequently associated with multiorgan dysfunction. Treatment relies on prompt diagnosis, delivery and supportive care. The clinical presentation may make the concurrent diagnosis and management of other disease entities challenging. This case report describes a patient with postpartum HELLP syndrome complicated by severe multiorgan dysfunction and pulmonary embolism.

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