Amniotic fluid embolism

Current concepts in the use of cell salvage in obstetrics

PURPOSE OF REVIEW

The worldwide leading cause of maternal death is severe maternal hemorrhage. Maternal hemorrhage can be profound leading to an entire loss of blood volume. In the past two decades, Patient Blood Management has evolved to improve patient's care and safety. In surgeries with increased blood loss exceeding 500 ml, the use of cell salvage is strongly recommended in order to preserve the patient's own blood volume and to minimize the need for allogeneic red blood cell (RBC) transfusion. In this review, recent evidence and controversies of the use of cell salvage in obstetrics are discussed.

RECENT FINDINGS

Numerous medical societies as well as national and international guidelines recommend the use of cell salvage during maternal hemorrhage.

SUMMARY

Intraoperative cell salvage is a strategy to maintain the patient's own blood volume and decrease the need for allogeneic RBC transfusion. Historically, cell salvage has been avoided in the obstetric population due to concerns of iatrogenic amniotic fluid embolism (AFE) or induction of maternal alloimmunization. However, no definite case of AFE has been reported so far. Cell salvage is strongly recommended and cost-effective in patients with predictably high rates of blood loss and RBC transfusion, such as women with placenta accreta spectrum disorder. However, in order to ensure sufficient practical experience in a multiprofessional obstetric setting, liberal use of cell salvage appears advisable.

Society of Family Planning Clinical Recommendation: Management of hemorrhage at the time of abortion

Hemorrhage after abortion is rare, occurring in fewer than 1% of abortions, but associated morbidity may be significant. Although medication abortion is associated with more bleeding than procedural abortion, overall bleeding for the two methods is minimal and not clinically different. Hemorrhage can be caused by atony, coagulopathy, and abnormal placentation, as well as by such procedure complications as perforation, cervical laceration, and retained tissue. Evidence for practices around postabortion hemorrhage is extremely limited. The Society of Family Planning recommends preoperative identification of individuals at high risk of hemorrhage as well as development of an organized approach to treatment. Specifically, individuals with a uterine scar and complete placenta previa seeking abortion at gestations after the first trimester should be evaluated for placenta accreta spectrum. For those at high risk of hemorrhage, referral to a higher-acuity center should be considered. We propose an algorithm for treating postabortion hemorrhage as follows: (1) assessment and examination, (2) uterine massage and medical therapy, (3) resuscitative measures with laboratory evaluation and possible reaspiration or balloon tamponade, and (4) interventions such as embolization and surgery. Evidence supports the use of oxytocin as prophylaxis for bleeding with dilation and evacuation; methylergonovine prophylaxis, however, is associated with more bleeding at the time of dilation and evacuation. Future research is needed on tranexamic acid as prophylaxis and treatment and misoprostol as prophylaxis. Structural inequities contribute to bleeding risk. Acknowledging how our policies hinder or remedy health inequities is essential when developing new guidelines and approaches to clinical services.

Fatal amniotic fluid embolism: incidence, risk factors and influence on perinatal outcome

PURPOSE

This study aimed to estimate the incidence of fatal amniotic fluid embolism, describe its risk factors, and analyze perinatal outcomes.

METHODS

Maternity cases and newborn records of amniotic fluid embolism were collected from the Zhejiang Maternal Surveillance System from October 2006 to October 2019. This study strictly limited the diagnostic criteria for AFE and excluded suspicious cases in order to minimize false-positive AFE cases. The risk factors of fatal amniotic fluid embolism and the relationship between perinatal prognosis and AFE were investigated using logistic regression analysis, estimating the adjusted odds ratios (aORs) and 95% confidence intervals (CIs).

RESULTS

149 cases of amniotic fluid embolism were registered, of which 80 cases were fatal. The estimated fatal AFE incidence was 0.99 per 100,000. The occurrence of fatal AFE was significantly correlated with spontaneous vaginal delivery (aOR 12.3, 95% CI 3.3-39.2) and cardiac arrest (aOR 64.8, 95% CI 14.6-287.8). The average diagnosis time of fatal AFE is 85.51 min, and the peak period of female death is 1-12 h after the onset of the disease, accounting for 60% (48/80) of cases. Fatal amniotic embolism is a cause of intrauterine fetal death and fetal death during delivery (aOR 11.957, 95% CI 1.457-96.919; aOR 13.152, 95% CI 1.636-105.723). Of the 149 confirmed AFE cases, 11 cases of stillbirth occurred, 12 cases were stillborn, and 7 cases of neonatal death were reported. The perinatal mortality rate was 202 per 1000.

CONCLUSIONS

Early detection, diagnosis, and treatment of amniotic fluid embolism are essential to avoiding fatal AFE. Clinicians should fully evaluate the pros and cons of choosing the delivery method for pregnant women. When cardiac arrest occurs in women with amniotic fluid embolism, obstetricians should be particularly careful and provide timely and effective treatment to minimize the fatality rate. The outcome of AFE is not only related to maternal survival but also plays a decisive role in the prognosis of the infant over the perinatal period.

Procoagulant Activity in Amniotic Fluid Is Associated with Fetal-Derived Extracellular Vesicles

Procoagulant activity in amniotic fluid (AF) is positively correlated with phosphatidylserine (PS) and tissue factor (TF)-expressing(+) extracellular vesicles (EVs). However, it is unknown if pathological fetal conditions may affect the composition, phenotype, and procoagulant potency of EVs in AF. We sought to evaluate EV-dependent procoagulant activity in AF from pregnant people with fetuses with or without diagnosed chromosomal mutations. AF samples were collected by transabdominal amniocentesis and assessed for common karyotype defects (total n = 11, 7 healthy and 4 abnormal karyotypes). The procoagulant activity of AF was tested using a fibrin generation assay with normal pooled plasma and plasmas deficient in factors XII, XI, IX, X, V, and VII. EV number and phenotype were determined by flow cytometry with anti-CD24 and anti-TF antibodies. We report that factor-VII-, X-, or V-deficient plasmas did not form fibrin clots in the presence of AF. Clotting time was significantly attenuated in AF samples with chromosomal mutations. In addition, CD24+, TF+, and CD24+ TF+ EV counts were significantly lower in this group. Finally, we found a significant correlation between EV counts and the clotting time induced by AF. In conclusion, we show that AF samples with chromosomal mutations had fewer fetal-derived CD24-bearing and TF-bearing EVs, which resulted in diminished procoagulant potency. This suggests that fetal-derived EVs are the predominant source of procoagulant activity in AF.

Recurrent Cardiac Arrests Due to Amniotic Fluid Embolism

Amniotic fluid embolism (AFE) is a rare but devastating complication of pregnancy and is associated with high morbidity and mortality. Identifiable maternal risk factors for AFE include older age, multiparity, cesarean section, and placenta previa, while fetal factors include male gender, fetal distress, and death. AFE presents with respiratory distress, seizure, and circulatory collapse and can be complicated with disseminated intravascular coagulopathy, multiorgan failure, and death. In our case, we present a patient who underwent elective cesarean section for placenta previa, which was complicated by sudden cardiac arrest immediately after delivering the placenta in the operating theatre followed by disseminated intravascular coagulation (DIC). The patient developed massive post-partum hemorrhage secondary to the underlying DIC, which required a massive blood transfusion along with platelets, fresh frozen plasma (FFP), and tranexamic acid. The Society of Maternal-Fetal Medicine proposed criteria for the diagnosis of AFE, which include clinical features and laboratory findings. The presence of a DIC picture is considered to be the hallmark finding that helps to differentiate between AFE and other conditions with similar presentation. Treatment of amniotic fluid embolism depends on early recognition and supportive care. 

Comparison of cell salvage with one and two suction devices during cesarean section in patients with placenta previa and/or accrete: a randomized controlled trial

Background

Cell salvage has recently been recommended for obstetric use in cases with a high risk of massive hemorrhage during cesarean section (CS). However, limited data are available to support the use of one suction device to collect lost blood. This study aimed to investigate the volume of red blood cells (RBCs) salvaged and the components of amniotic fluid (AF) in blood salvaged by one suction device or two devices during CS in patients with placenta previa and/or accrete.

Methods

Thirty patients with placenta previa and/or accrete undergoing elective CS in the Women's Hospital of Zhejiang University School of Medicine were recruited for the present study from November 1, 2017 to December 1, 2018. The patients were randomly assigned to one of the two groups according to an Excel-generated random number sheet: Group 1 (n = 15), in which only one suction device was used to aspirate all blood and AF, and Group 2 (n = 15), in which a second suction device was mainly used to aspirate AF before the delivery of the placenta. Three samples of blood per patient (pre-wash, post-wash, and post-filtration) were collected to measure AF components. The salvaged RBC volumes were recorded. Continuous data of pre-wash, post-wash, and post-filtration samples were analyzed by using one-way analysis of variance with Tukey's test for multiple comparisons, or Kruskal-Wallis test with Dunn test for multiple comparisons. Comparisons of continuous data between Group 1 and Group 2 were conducted using Student's t test or Mann-Whitney U test.

Results

The salvaged RBC volume was significantly higher in Group 1 than that in Group 2 (401.6 ± 77.2 mL vs. 330.1 ± 53.3 mL, t = 4.175, P < 0.001). In both groups, squamous cells, lamellar bodies, and fat were significantly reduced by washing (all P<0.001) and squamous cells were further reduced by filtering (P < 0.001). Squamous cells were found in six post-filtration samples (three from each group). Lamellar bodies and fat were completely removed by filtering. Insulin-like growth factor binding protein 1, alpha-fetoprotein, albumin, lactate dehydrogenase, and potassium were significantly reduced post-wash (all P < 0.05), with no further significant reduction after filtration in either group (all P > 0.05). The mean percentage of fetal RBCs post-filtration was (1.8 ± 0.8)% with a range of 1.0% to 3.5% and (1.9 ± 0.9)% with a range of 0.7% to 4.0% in Groups 1 and 2, respectively, showing no significant difference between the two groups (U = 188.5, P = 0.651).

Conclusion

Cell salvage performed by one suction device could result in higher volume of salvaged RBCs and can be used safely for CS in patients with placenta previa and/or accrete when massive hemorrhage occurs.

Trial registration number

ChiCTR-INR-17012926, http://www.chictr.org.cn/ Chinese Clinical Trial Registry.

Resuscitation of the Pregnant Patient

Many health care providers lack familiarity with maternal physiologic changes and the distinctive underlying etiology of cardiac arrest in pregnancy. Knowledge of what changes are expected in pregnancy and an understanding of how to adapt clinical practice is essential for the care of the pregnant woman in the emergency department. Amniotic fluid embolism should be recognized as a rare cause of cardiac arrest in pregnancy, characterized by the triad of cardiovascular collapse, hypoxic respiratory failure, and coagulopathy. Cardiopulmonary resuscitation should follow standard AHA ACLS guidelines. Resuscitative hysterotomy may be attempted to restore perfusion to both mother and fetus.

Amniotic fluid embolism and spontaneous hepatic rupture during uncomplicated pregnancy: a case report and literature review

Amniotic fluid embolism (AFE) and spontaneous hepatic rupture both are extremely rare complications of pregnancy that can be fatal to mother and/or child. AFE is characterized by a sudden collapse of the cardiovascular system, a change in mental status, and disseminated intravascular coagulation (DIC), occurring immediately during labor, delivery, or postpartum, caused by the inflow of amniotic components into the maternal circulation. Spontaneous hepatic rupture during pregnancy which is most often occurs alongside hypertensive disorders, eclampsia, or HELLP syndrome. We report on the case of a 28-year-old woman (G3P2) who is suffering from AFE and spontaneous hepatic rupture, without history of hypertensive disorders, preeclampsia/eclampsia, or HELLP syndrome, and she died suddenly after delivering of a severe asphyxial neonate within 1 h with postpartum of hepatic rupture and massive hemorrhage. The lack of typical clinical signs and symptoms resulted to the difficulty of early diagnosis. If AFE and hepatic rupture is highly suspected in a pregnant patient, a collaborative multidisciplinary approach is mandatory. Pregnancy women is simultaneously complicated in amniotic fluid embolism and spontaneous hepatic rupture, similar cases are infrequent in the literature, which is reviewed in this report, explore the pathophysiological changes, we hope that can be helpful for the prevention, diagnosis and treatment of similar cases.

How about "The effect of intraoperative cell salvage on allogeneic blood transfusion for patients with placenta accreta"?: An observational study

Intraoperative cell salvage (IOCS) for high-risk obstetric hemorrhage is now endorsed by a number of obstetric organizations. Most previous studies have focused on the safety of IOCS from case series and small controlled studies. Here, we describe the effect of IOCS on rates of allogeneic blood transfusion (ABT) under different degrees of bleeding during cesarean section in women with placenta accreta, which has seldom been reported in the literature.We conducted a retrospective analysis on the introduction of routine application of IOCS for the management of hemorrhage during cesarean section in women with placenta accreta. We identified 115 women, with prenatally diagnosed placenta accreta/increta/percreta before this change in practice, who served as controls, and 108 women who had IOCS applied during cesarean section.Compared with the control treatment, IOCS was significantly associated with a lower incidence of ABT (odds ratio, 0.179; 95% confidence interval, 0.098-0.328). Among the women with ≤3000 mL of bleeding, ABT was avoided in 80 (93.0%) of the 86 patients in the IOCS group, while 49 (50.0%) of the 98 controls required ABT. For women with an estimated blood loss >3000 mL, the reinfused IOCS blood may have helped prevent the need for ABT in 6 (28.6%) of the 21 patients, while all of the 17 controls required ABT. Subgroup analysis of coagulation function and the need for coagulation components showed no significant difference between the 2 groups (P > .05). Compared with the control treatment, IOCS was associated with a lower intraoperative volume of crystalloid (P < .01) and colloid infusion (P < .01) and a shorter length of postoperative hospital stay (P < .01) in patients with placenta accreta. In addition, there were no complications or adverse reactions in patients with placenta accreta who underwent IOCS.IOCS helped reduce the need for ABT and fluid transfusion in patients with placenta accreta and may be safe for use in obstetrics.

Atypical Amniotic Fluid Embolism Managed with a Novel Therapeutic Regimen

Amniotic fluid embolism (AFE) is the second leading cause of maternal mortality in the USA with an incidence of 1 : 15,200 births. The case fatality rate and perinatal mortality associated with AFE are 13–30% and 9–44%, respectively. This rare but devastating complication can be difficult to diagnose as many of the early signs and symptoms are nonspecific. Compounding this diagnostic challenge is a lack of effective treatment regimens which to date are mostly supportive. We present the case of a 26-year-old woman who suffered from suspected AFE and was successfully treated with the novel regimen of Atropine, Ondansetron, and Ketorolac (A-OK). The authors acknowledge that this case does not meet the new criteria proposed, by Clark in 2016, but feel that it is important to share this case report, due to dramatic patient response to the provided supportive therapy presented in this case report. We hope this case report will prompt further research into this novel approach to treating AFE with Atropine, Ondansetron, and Ketorolac.

Amniotic Fluid Embolism. Is a New Pregnancy Possible? Case Report

Amniotic fluid embolism (AFE) is a rare but potentially catastrophic clinical condition, characterized by a combination of signs and symptoms that reflect respiratory distress, cardiovascular collapse and disseminated intravascular coagulation (DIC). Its pathogenesis is still unclear. More recently, the traditional view of obstruction of pulmonary capillary vessels by amniotic fluid emboli as the main explanation for the etiology has been ruled out, and immunologic factors and the activation of the inflammatory cascade took on an important role. Amniotic fluid embolism has an unpredictable character, its diagnosis is exclusively clinical, and the treatment consists mainly of cardiovascular support and administration of blood products to correct the DIC. No diagnostic test is recommended until now, though multiple blood markers are currently being studied. The authors present a case report of a woman who had survived AFE in her previous pregnancy and had a subsequent pregnancy without recurrence, providing one more clinical testimony of the low risks for the pregnancy after AFE.

Amniotic Fluid Embolism

Amniotic fluid embolism (AFE) is a rare but serious and potentially deadly complication of pregnancy that is unpreventable and unpredictable. Most AFE events occur during labor; however, approximately one third happen during the immediate postpartum period. Presentation is abrupt and thought to be an abnormal response to fetal materials entering maternal circulation through the placental insertion site. Care providers must recognize the signs and symptoms of AFE and react quickly to treat potential complications. This can be challenging as there are no set diagnostic criteria or specific laboratory tests. Generally, the diagnosis is based on clinical status when the classic triad of hypoxia, hypotension, and subsequent coagulopathy are noted in a laboring woman or woman who just gave birth, and no other plausible explanation can be determined. Proper treatment of AFE requires a multidisciplinary approach to decrease maternal morbidity and mortality. Knowledge, simulation, and familiarization of a Massive Obstetric Transfusion protocol can help all members of the perinatal team recognize and respond to women with AFE in a timely and effective manner. A case study is presented of a woman with a seemingly normal obstetric course that became complicated rapidly following development of an AFE.

Amniotic fluid embolism

Amniotic fluid embolism (AFE) is one of the catastrophic complications of pregnancy in which amniotic fluid, fetal cells, hair, or other debris enters into the maternal pulmonary circulation, causing cardiovascular collapse. Etiology largely remains unknown, but may occur in healthy women during labour, during cesarean section, after abnormal vaginal delivery, or during the second trimester of pregnancy. It may also occur up to 48 hours post-delivery. It can also occur during abortion, after abdominal trauma, and during amnio-infusion. The pathophysiology of AFE is not completely understood. Possible historical cause is that any breach of the barrier between maternal blood and amniotic fluid forces the entry of amniotic fluid into the systemic circulation and results in a physical obstruction of the pulmonary circulation. The presenting signs and symptoms of AFE involve many organ systems. Clinical signs and symptoms are acute dyspnea, cough, hypotension, cyanosis, fetal bradycardia, encephalopathy, acute pulmonary hypertension, coagulopathy etc. Besides basic investigations lung scan, serum tryptase levels, serum levels of C3 and C4 complements, zinc coproporphyrin, serum sialyl Tn etc are helpful in establishing the diagnosis. Treatment is mainly supportive, but exchange transfusion, extracorporeal membrane oxygenation, and uterine artery embolization have been tried from time to time. The maternal prognosis after amniotic fluid embolism is very poor though infant survival rate is around 70%.

From appearance to essence: 10 years review of atypical amniotic fluid embolism

PURPOSE

Amniotic fluid embolism (AFE) is an unpredictable and unpreventable complication of maternity. The presentation may range from relatively subtle clinical events to sudden maternal cardiac arrest. However, the neglected diagnosis of non-classical form of AFE (atypical AFE) is very common. The aim of this study was to examine population-based regional data from Suzhou, China. Based on the analysis of all available case reports, we put forward an outline of atypical AFE and investigate whether any variation identified could be ascribed to methodology.

METHODS

Retrospective study from January 2004 to December 2013, 53 cases was identified from the database of Center for Disease Control (CDC) in the city of Suzhou. We investigated the presentations of atypical AFE and maternal characteristics with potential factors underlying AFE. Multiple-regression analysis was used to calculate adjusted odds ratios (ORs) and 95 % confidence intervals (CIs).

RESULTS

The incidence of AFE was 6.91 per 100,000 deliveries (53/766,895). Seventeen deaths occurred, a mortality rate of 32 %. Atypical AFE may as the earlier stage or mild form of AFE, there was no death case in the study with timely remedy. The atypical AFE appear is obstetric hemorrhage and/or pulmonary and renal dysfunction postpartum. Hyperfibrinolysis and coagulopathy may the early laboratory findings of atypical AFE. Atypical and classical AFE shared the same risks, such as advanced maternal age, placental abnormalities, operative deliveries, eclampsia, cervical lacerations, and induction of labor.

CONCLUSION

Staying alert to premonitory symptoms of AFE is critical to turn it to a remediable disease. Patient complaints such as breathlessness, chest pain, feeling cold, distress, panic, a feeling of nausea, and vomiting should elicit close attention. The management of a suspected episode of amniotic fluid embolism is generally considered to be supportive. Hysterectomy must be performed if there is further progression of symptoms. Due to advances in acute care, mortality has decreased in recent years, highlighting the importance of early detection and treatment.

Amniotic fluid embolism: an interdisciplinary challenge: epidemiology, diagnosis and treatment

BACKGROUND

Amniotic fluid embolism (AFE) is a life-threatening obstetric complication that arises in 2 to 8 of every 100 000 deliveries. With a mortality of 11% to 44%, it is among the leading direct causes of maternal death. This entity is an interdisciplinary challenge because of its presentation with sudden cardiac arrest without any immediately obvious cause, the lack of specific diagnostic tests, the difficulty of establishing the diagnosis and excluding competing diagnoses, and the complex treatment required, including cardio - pulmonary resuscitation.

METHOD

We selectively reviewed pertinent literature published from 2000 to May 2013 that was retrieved by a PubMed search.

RESULTS

The identified risk factors for AFE are maternal age 35 and above (odds ratio [OR] 1.86), Cesarean section (OR 12.4), placenta previa (OR 10.5), and multiple pregnancy (OR 8.5). AFE is diagnosed on clinical grounds after the exclusion of other causes of acute cardiovascular decompensation during delivery, such as pulmonary thromboembolism or myocardial infarction. Its main clinical features are severe hypotension, arrhythmia, cardiac arrest, pulmonary and neurological manifestations, and profuse bleeding because of disseminated intravascular coagulation and/or hyperfibrinolysis. Its treatment requires immediate, optimal interdisciplinary cooperation. Low-level evidence favors treating women suffering from AFE by securing the airway, adequate oxygenation, circulatory support, and correction of hemostatic disturbances. The sudden, unexplained death of a pregnant woman necessitates a forensic autopsy. The histological or immunohistochemical demonstration of formed amniotic fluid components in the pulmonary bloodflow establishes the diagnosis of AFE.

CONCLUSION

AFE has become more common in recent years, for unclear reasons. Rapid diagnosis and immediate interdisciplinary treatment are essential for a good outcome. Establishing evidence-based recommendations for intervention is an important goal for the near future.

Acute hypotension associated with intraoperative cell salvage using a leukocyte depletion filter during management of obstetric hemorrhage due to amniotic fluid embolism

Amniotic fluid embolism (AFE) is a rare but catastrophic obstetric complication that can lead to profound coagulopathy and hemorrhage. The role of cell salvage and recombinant human Factor VIIa (rFVIIa) administration in such cases remains unclear. We present a case of AFE and describe our experience with the use of cell salvage and rFVIIa administration during the resuscitation. Cell salvage and transfusion through a leukocyte depletion filter was attempted after the diagnosis of AFE was made, but the attempted transfusion was immediately followed by hypotension and a worsening of hemodynamics. rFVIIa, on the contrary, was used with clinical improvement in coagulopathy and without apparent adverse thrombotic effect.

The use of therapeutic hypothermia in the management of amniotic fluid embolism

Background:

Amniotic fluid embolism (AFE) is a rare peripartum obstetric emergency where patients seldom survive neurologically intact. The exact pathophysiology is not completely understood and treatment remains mainly supportive.

Case:

A 34-year-old African American woman gravida 1, para 0-0-0-0 at 38 weeks and four days induced for chronic hypertension with superimposed preeclampsia experienced an AFE during labour. Supportive treatment included early use of therapeutic hypothermia resulting in a normal neurological outcome.

Conclusion:

This case demonstrates the timely use of therapeutic hypothermia in a patient surviving an AFE and suffering no neurological sequelae. Therapeutic hypothermia should be considered in the supportive treatment of AFE.

Amniotic fluid induces platelet-neutrophil aggregation and neutrophil activation

OBJECTIVE

Amniotic fluid embolism syndrome is a fatal disease in pregnant women. The exact role of platelets and neutrophils in amniotic fluid embolism syndrome is not clear. We examined whether amniotic fluid could affect platelet-neutrophil aggregation and activation and the possible mechanisms.

STUDY DESIGN

Blood samples from the pregnant women were pretreated ex vivo with their own amniotic fluid. Flow cytometry was used to measure platelet-neutrophil aggregation and activation. Neutrophil-mediated activity of p38 mitogen-activated protein kinase and extracellular signal-regulated protein kinases 1 and 2 was analyzed by Western blotting.

RESULTS

Amniotic fluid significantly induced platelet-neutrophil aggregation, neutrophil CD11b expression, and reactive oxygen species production. Amniotic fluid induced minimal platelet P-selectin expression. The increase of intracellular calcium level of neutrophils and the activity of p38 mitogen-activated protein kinase were enhanced by amniotic fluid stimulation.

CONCLUSION

Amniotic fluid was able to induce neutrophil activation and platelet-neutrophil aggregation with minimal effect on platelet activation. These findings may provide a new insight in the understanding of the pathophysiologic condition of amniotic fluid embolism syndrome.

Electrical impedance tomography may optimize ventilation in a postpartum woman with respiratory failure

Amniotic fluid embolism is a rare peripartum complication with the sudden onset of haemodynamic instability, respiratory failure and coagulopathy during labour or soon after delivery. A 31-year-old woman with amniotic fluid embolism was treated with vasopressors, inotropes, intravenous fluid, tranexamic acid and ventilatory support. Assessment of respiratory impairment was made using conventional chest X-ray, computed tomography and electrical impedance tomography. The potential for electrical impedance tomography to improve monitoring and guide respiratory therapy is explored.

The introduction of intra-operative cell salvage in obstetric clinical practice: a review of the available evidence

Intra-operative blood salvage is common practice in many surgical specialties but its safety is questioned with concerns about the risks of contamination of recovered blood with amniotic fluid and of maternal-foetal alloimmunization. However, the role of cell salvage as a blood-saving measure in this clinical setting is progressively acquiring relevance thanks to the growing body of evidence regarding its quality and safety. Modern cell savers remove most particulate contaminants and leukodepletion filtering of salvaged blood prior to transfusion adds further safety to this technique. Amniotic fluid embolism is no longer regarded as an embolic disease and the contamination of the salvaged blood by foetal Rh-mismatched red blood cells can be dealt with using anti-D immunoglobulin; ABO incompatibility tends to be a minor problem since ABO antigens are not fully developed at birth. Maternal alloimmunization can be caused also by other foetal red cell antigens, but it should also be noted that the risk of alloimmunization of the mother from allogeneic transfusion may be even greater. Therefore the use of cell savers in obstetric clinical practice should be considered in patients at high risk for haemorrhage or in cases where allogeneic blood transfusion is difficult or impossible.