**29. Amniotic fluid embolism**

AFE is an exceedingly rare and one of the most catastrophic complications of pregnancy. It remains an enigma to this date, more than half a century after the first published autopsy series. AFE is responsible for significant proportion of maternal mortality (Lang & King, 2008; Lewis, 2007). The presence of fetal debris in the pulmonary circulation of a mother who died suddenly during labor was first reported by Meyer in 1926 (Meyer, 1926) and

1) Size of emboli Larger Smaller

2) Air

1) Cavitation

nodules 3) Peripheral

Echocardiography is an important tool in evaluating patients for endocarditis. Transesophageal echocardiography (TEE) increases the sensitivity of detecting vegetations from 75 to 95 percent while maintaining the specificity of 85 to 98 percent and is thus, superior to the transthoracic technique (TTE) in delineating vegetations, abscesses and leaflet

Recent studies demonstrate improved outcomes for patients with SPE with virtually all patients recovering from their illness. This may be attributable to earlier diagnosis, prompt administration of broad-spectrum antibiotics and improvements in surgical and supportive care. Discontinuation of vascular catheters/devices is recommended. In Lemierre's syndrome, vigorous antibiotic treatment for 4-6 weeks, targeting the organism and drainage of accessible abscesses are indicated. Internal jugular vein ligation/excision is rarely indicated as is the use of anticoagulation (Armstrong et al., 2000; Lustig et al., 1995). Consensus recommendation(American Heart Association (AHA), British Society for Antimicrobial Chemotherapy (BSAC), and the European Society for Cardiology (ESC)) is that, prompt use of antibiotics in treatment of endocarditis may result in reduction of incidence of SPE (Baddour et al., 2005; Elliott et al., 2004). The recommended duration of antibiotics is 4 to 6 weeks. The 2008 American College of Chest Physicians (ACCP) guidelines recommend against the use of routine antithrombotic therapy unless a separate

AFE is an exceedingly rare and one of the most catastrophic complications of pregnancy. It remains an enigma to this date, more than half a century after the first published autopsy series. AFE is responsible for significant proportion of maternal mortality (Lang & King, 2008; Lewis, 2007). The presence of fetal debris in the pulmonary circulation of a mother who died suddenly during labor was first reported by Meyer in 1926 (Meyer, 1926) and

2) Radiographic Characteristics

Table 7. Characteristics of SPE

**28. Treatment** 

indication exists.

**29. Amniotic fluid embolism** 

perforations in the heart (Dodd et al., 2006).

**Features Gram Positive SPE Gram negative SPE** 

bronchograms in

1) 'Halo sign': Central area of soft tissue attenuation surrounded by a halo of groundglass attenuation.

2) Hemorrhagic

sign

3) "Feeding vessel"

nodules and infarcts

wedge shaped opacities

subsequently by Steiner and Lushbaugh in 1941 as an autopsy series (Steiner & Lushbaugh, 1941).

#### **30. Epidemiology and risk factors**

The true incidence of AFE remains unknown and is variably reported in literature. The incidence of AFE has been estimated to be in 1 in 8000 to 80000 deliveries with reported mortality rates in older reports as high as 60%. However, more recent data suggest lower mortality rates ranging between 27-37% (Clark et al., 1995; Morgan, 1979; Tuffnell, 2005). For unknown reasons, the incidence of AFE is much higher in North America, around 1 in 15000 deliveries, Australia -1 in 30000 deliveries (C. L. Roberts et al., 2010), United Kingdom – 1 in 50000 (Abenhaim et al., 2008; Knight et al., 2010; Kramer et al., 2006).

AFE usually occurs during immediate postpartum period. Data from a national registry revealed that AFE occurred during labor but before delivery in 70% of cases and during caesarean section in 19% (Clark et al., 1995). Although, reported as early as second trimester, the diagnosis in cases occurring as late as 36 h postpartum has been described (Devriendt et al., 1995). AFE following trans-abdominal amniocentesis is very rare (Hasaart & Essed, 1983). It has been estimated that AFE accounted for 12% of all maternal deaths related to legally induced abortion since 1972 (Grimes & Schulz, 1985; Guidotti et al., 1981). It is seldom associated with (surgical) manipulation during caesarean section (Laforga, 1997), curettage (Grimes & Cates, 1977), cervical suture removal (Margan et al., 1984) or repair of an incompetent cervix (Margan et al., 1984), or after car or motor vehicle accidents (Olcott et al., 1973). Large fetal size, use of oxytocics and vaginal prostaglandins, advanced gestational age, amnio-infusion or complicated labor have all been implicated (Maher et al., 1994; Morgan, 1979). In reality, specific risk factors have not been conclusively identified. Logistic regression identified advanced maternal age, placental pathologies and caesarean deliveries in a large population-based cohort study (Abenhaim et al., 2008). Maternal age below 20 years and dystocia has been associated with lower incidence of AFE.

Pathophysiology: The pathogenesis of AFE remains poorly understood. The detection of fetal tissue in maternal pulmonary artery is not pathognomonic. In fact, there is no clear temporal relationship between entry of amniotic fluid in to maternal circulation and symptom onset. The "antigenic" nature of AF along with pulmonary eosinophilic infiltrates, elevated antitryptase activity suggestive of mast cell degranulation has resulted in some authors to propose "Anaphylactoid syndrome of Pregnancy" as an alternative name to AFE. Autopsy findings frequently reveal disseminated intravascular coagulation (DIC). Isolated DIC may herald AFE. Amniotic fluid accelerates clot initiation and propagation.

Hemodynamic Effects: A biphasic pattern of hemodynamic changes have been favored in most recent descriptions. The "acute phase" comprising of acute elevation of pulmonary arterial pressure ("acute Cor Pulmonale"), followed by left ventricular dysfunction/failure.

#### **31. Clinical features**

AFE is a diagnosis of exclusion. It typically occurs during labor and delivery or in the immediate postpartum period, although it can occur as late as 48 hours postpartum. About 70% of cases occur before delivery (range, 63–76%). The symptoms are often sudden and protean. AFE is typified by maternal collapse associated with breathlessness, cyanosis, cardiac dysrhythymia, hypotension and then haemorrhage associated with DIC. Clark et al,

Non-Thrombotic Pulmonary Embolism 93

seizures or coma, DIC and in absence of potential alternative explanation for these manifestations (Table 2). Demonstration of fetal squamous cells in pulmonary arterial circulation is not pathognomonic. Presence of AF cells in BAL may be supportive. There are no specific laboratory tests for diagnosing AFE. Diagnostic markers for AFE have been developed which rely on detection of fetal or amniotic fluid constituents in maternal circulation, such as Serum Sialyl Tn Antigen, (Benson et al., 2001; Kobayashi et al., 1993; Oi et al., 1998) and plasma zinc coproporphyrin (a component of meconium) (Kanayama et al., 1992). Serum Tryptase, a marker of mast cell degranulation may be elevated but unreliable

There is no specific treatment for AFE. The condition can be neither predicted nor prevented. The principles of management of AFE are mainly supportive, ie, to restore and maintain hemodynamic stability, to correct hypoxia and maintain adequate oxygenation, correction of coagulopathy with blood products as necessary and to deliver the fetus promptly at the earliest sign of maternal or fetal distress. Given sudden or hyperacute manner of presentation, prompt and aggressive response from the treating clinician is a must. As the diagnosis is not always clear from the onset of collapse, the role of diagnostic tests is to exclude conditions that can be treated specifically such as, Thrombotic PE which is more common compared to AFE. Hypoxia must be corrected promptly as significant proportions of survivors have residual neurological impairment due to cerebral anoxia (Moore & Baldisseri, 2005). Hypotension and shock should be aggressively treated with intravenous fluids, vasopressors and ionotropes as necessary. Since clinical manifestations are biphasic and complex, invasive hemodynamic monitoring is essential. Additional data from trans-thoracic or trans-esophageal echocardiography may be useful (James et al., 2004; Koegler et al., 1994; Stanten et al., 2003; van Haeften et al., 1989; Verroust et al., 2007). Administration of blood component is considered the first line treatment for coagulopathy associated with AFE. DIC is frequently associated with severe hemorrhage, so transfusion of packed red blood cells is a priority to maintain adequate tissue oxygenation. Uterine atony with DIC is a dangerous complication that might require immediate surgical intervention

As AFE occurred during labor in a predominant number of cases, immediate delivery of fetus by means of caesarian section is mandatory to prevent fetal hypoxic damage and to facilitate resuscitation (Davies & Harrison, 1992; Prasad & Howell, September 2001). Advanced cardiac life support (ACLS) protocol should be followed in case of cardiac arrest. The goal of drug therapy is to restore normal maternal hemodynamics in conjunction with the delivery of the fetus as soon as possible after the onset of asystole or malignant arrhythmia. During resuscitation, the uterus should be displaced to the left to avoid

AFE accounts for approximately 10% of all maternal death within the USA (Atrash et al., 1990). Case fatality rate has declined significantly in recent years due to the prompt and aggressive resuscitation measures. (Abenhaim et al., 2008; Benson, 1993; Clark et al., 1995; Morgan, 1979). There is higher likelihood of survival if the women survive long enough to

compression of the large vessels and improve venous return.

(Dorne et al., 2002; Farrar & Gherman, 2001; Marcus et al., 2005; Nishio et al., 2002).

**33. Management** 

such as, hysterectomy.

**34. Prognosis** 


Table 8. Risk factors associated with an increased risk of AFE in two large registries.

found the most common presenting signs and symptoms were hypotension and signs of non-reassuring fetal status (100%), pulmonary edema or respiratory symptoms (93%), cardiac arrest (87%), cyanosis (83%), and coagulopathy (83%). A majority develop seizures, encephalopathy and permanent neurological sequelae [85], due to cerebral ischemia and anoxia. The clinical course seems to have phases that are likely temporally related to pathophysiologic changes (Clark, 1990).


Table 9. Procedures associated with AFE.
