Embolism during pregnancy: thrombus, air, and amniotic fluid

Cardiogenic shock in pregnancy

Cardiac disease complicates 1%-4% of pregnancies globally, with a predominance in low and middle-income countries (LMICs). Increasing maternal age, rates of obesity, cardiovascular comorbidities, pre-eclampsia and gestational diabetes all contribute to acquired cardiovascular disease in pregnancy. Additionally, improved survival in congenital heart disease (CHD) has led to increasing numbers of women with CHD undergoing pregnancy. Implementation of individualised care plans formulated through pre-conception counselling and based on national and international guidance have contributed to improved clinical outcomes. However, there remains a significant proportion of women of reproductive age with no apparent comorbidities or risk factors that develop heart disease during pregnancy, with no indication for pre-conception counselling. The most extreme manifestation of cardiac disease is cardiogenic shock (CS), where the primary cardiac pathology results in inadequate cardiac output and hypoperfusion, and is associated with significant mortality and morbidity. Key to management is early recognition, intervention to treat any potentially reversible underlying pathology and supportive measures, up to and including mechanical circulatory support (MCS). In this narrative review we discuss recent developments in the classification of CS, and how these may be adapted to improve outcomes of pregnant women with, or at risk of developing, this potentially lethal condition.

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%.

Pulmonary Embolic Disorders

Deaths due to pulmonary thromboemboli are frequently encountered by the forensic pathologist and account for a significant percentage of sudden, unexpected deaths. Diagnosing these straightforward cases is often not a challenge, but unfortunately some cases in which a thromboembolism is expected can become complicated. Occasionally, a postmortem clot may mimic a thromboembolism and lead to a mistaken diagnosis, and in other situations it may become paramount to attempt to age a thrombus as part of a medicolegal lawsuit. Additionally, many individuals use the less specific term, “pulmonary emboli”, when referring to these cases in which a portion of a thrombus, usually originating in the deep veins of the lower extremities, breaks off and travels to the pulmonary vasculature bed where it occludes vessels and leads to a rapid demise. One must remember, though, that several other materials and tissues including fat, amniotic fluid, air, tumors, solid organs, synthetic materials, and parasites may be displaced and embolize to the lungs and cause significant disease. In the following pages we will provide a thorough review of pulmonary embolic disorders, focusing on those diseases most likely to be encountered by the forensic pathologist. The aim of this review is to aid the pathologist in using proper terminology, diagnosing various types of embolic disorders, and recognizing potential mimics.

Extraabdominal vs intraabdominal uterine repair at cesarean delivery: a metaanalysis

OBJECTIVE

Cesarean section delivery is a commonly performed surgical procedure, and rates of cesarean delivery are increasing. Previous randomized trials that compared extraabdominal and intraabdominal uterine repair at cesarean section delivery have yielded conflicting results.

STUDY DESIGN

We conducted a metaanalysis of published randomized controlled trials that addressed the method of uterine repair at cesarean delivery. The primary outcome was incidence of perioperative complications. The secondary outcomes were operative time, estimated blood loss, and hospital stay. Pooled odds ratios were calculated for categoric variables with random effects models. Continuous variables were compared by means of weighted mean differences.

RESULTS

No significant differences in either postoperative or intraoperative complications were demonstrated between the extraabdominal (n = 1605) and intraabdominal repair (n = 1578) groups. Operative time, estimated blood loss, and hospital stay were all unaffected by repair technique. This study cannot exclude differences in rare complications, such as serious venous air embolism or maternal death.

CONCLUSION

No differences in complication rates were found between extraabdominal and intraabdominal repair at cesarean section delivery; both techniques are valid surgical options.

Cardiac arrest and pregnancy

Cardiopulmonary arrest in pregnancy is rare occurring in 1 in 30,000 pregnancies. When it does occur, it is important for a clinician to be familiar with the features peculiar to the pregnant state. Knowledge of the anatomic and physiologic changes of pregnancy is helpful in the treatment and diagnosis. Although the main focus should be on the mother, it should not be forgotten that there is another potential life at stake. Resuscitation of the mother is performed in the same manner as in any other patient, except for a few minor adjustments because of the changes of pregnancy. The specialties of obstetrics and neonatology should be involved early in the process to ensure appropriate treatment of both mother and the newborn. This article will explore the changes that occur in pregnancy and their impact on treatment. The common causes of maternal cardiac arrest will be discussed briefly.

Acute non-traumatic maternal illnesses in pregnancy: imaging approaches

The imaging methods used to obtain diagnostic information for pregnant patients presenting with acute non-traumatic maternal illnesses have been reviewed. Conditions affecting the gastrointestinal tract, urinary tract, uterus, adnexae, central nervous system and chest have been investigated via a variety of imaging methods, which include ultrasound, computed tomography (CT), magnetic resonance imaging (MRI), intravenous pyelography (IVP), angiography and fluoroscopy. The method of choice, application, and safety to the mother and fetus are considered for investigation of each condition.

What’s new and novel in obstetric anesthesia? Contributions from the 2003 scientific literature

THE PREGNANT PATIENT: Age; maternal disease; prophylactic antibiotics; gastroesophageal reflux; obesity; starvation; genotyping; coagulopathy; infection; substance abuse; altered drug responses in pregnancy; physiological changes of pregnancy. THE FETUS: Fetal monitoring; intrauterine surgery. THE NEWBORN: Breastfeeding; maternal infection, fever, and neonatal sepsis evaluation. OBSTETRIC COMPLICATIONS: Embolic phenomena; hemorrhage; preeclampsia; preterm delivery. OBSTETRIC MANAGEMENT: External cephalic version and cervical cerclage; elective cesarean delivery; fetal malpresentation; vaginal birth after cesarean delivery; termination of pregnancy. OBSTETRIC ANESTHESIA: Analgesia for labor and delivery; anesthesia for cesarean delivery; anesthesia for short obstetric operations; complications of anesthesia. MISCELLANEOUS: Consent; ethics; history; labor support; websites/books/leaflets/journal announcements.

Effect of increasing doses of magnesium in experimental pulmonary hypertension after acute pulmonary embolism

OBJECTIVE

To investigate the dose-related effects of magnesium on pulmonary vascular resistance and associated changes in cardiac output in porcine micro-embolic pulmonary hypertension.

DESIGN

Prospective, interventional animal study.

SETTING

University animal laboratory.

SUBJECTS

Forty anaesthetised and ventilated piglets.

INTERVENTIONS

Right heart catheterisation for the measurement of cardiac output, pulmonary artery pressure, central venous pressure and pulmonary capillary wedge pressure; arterial cannulation for measurement of arterial pressures and ionised magnesium levels; calculation of pulmonary and systemic vascular resistance before and after induction of acute pulmonary micro-embolism, and without or with the administration of magnesium (0.5, 1.0, 2.0 mmol/kg bolus and 1 mmol/kg bolus followed by 1 mmol/kg per h continuous infusion).

MEASUREMENTS AND MAIN RESULTS

The bolus administration of increasing doses of magnesium (0.5, 1.0, 2.0 mmol/kg) was associated with an increase in ionised serum magnesium levels and a dose-dependent decrease of mean pulmonary arterial pressure, an increase of cardiac output and a decrease of pulmonary vascular resistance. This effect was sustained after bolus administration (1 mmol/kg) followed by a continuous infusion of magnesium (1 mmol/kg per h).

CONCLUSIONS

Magnesium has a directly dose-dependent beneficial effect on the circulation in acute embolic pulmonary hypertension and improves cardiocirculatory impairment in massive pulmonary embolism (PE).

Pulmonary complications of pregnancy

Pregnancy induces significant physiologic stresses on the pulmonary and cardiovascular systems that may precipitate respiratory compromise. In addition, certain disease states that are unique to the pregnant woman, such as amniotic fluid emboli syndrome, may be associated with respiratory failure. The physiologic changes that affect the pregnant woman are reviewed. Pregnancy-related conditions are discussed as well as how common diseases, such as the acute respiratory distress syndrome, asthma, pneumonia, and AIDS,have to be approached when balancing the needs of the fetus with maternal well-being.