武功密笈

小黃藏書

Recently, the term anaphylactoid syndrome of pregnancy has been proposed

instead of AFE (amniotic fluid embolism), to better characterize this condition as

a multisystemic reaction to toxins rather than an embolic phenomenon.

z True incidence of AFE: may not be known, 1/8000 to 1/83000 deliveries

z Growing awareness of the syndrome, rather than a true increase in incidence or idiosyncrasies

z AFE constitute the leading cause of mortality during labor and the first few postpartum hours.

z 5% to 18% of all maternal deaths are due to AFE.

z 7.8 to 12 deaths per million births

z For women diagnosed as having AFE, mortality rates ranging from 26% to

86% have been reported.

z Anaphylaxis plays a role in the syndrome.

z Clinically, the reaction to AFE comprises three distinct phases. Besides, the

syndrome seems to have a logarithimic presentation with decreasing

intensity, frequency, and mortality as time elapses from the onset of

symptoms. If a patient survives with or without intervention, the morbidity

and mortality are dramatically lower.

z The first phase:

Cardiogenic and noncardiogenic pulmonary edema

1). Blue phase: respiratory, including respiratory distress and cyanosis

2). White phase: hemodynamic, with pulmonary edema and shock

3). Neurologic, including seizures, confusion or coma

ø These presentations can occur separately or in combination, and indifferent degrees

z The second phase:

1). Intravascular coagulopathy

2). Red phase: hemorrhage

z The third phase: Gray phase

­ The acute symptoms are over and tissue injury (brain, lung, or renal) is for

the most part already established.

­ During this convalescent period, which may last weeks, affected patients

can die as a result of severe lung or brain injury, multisystemic organ

failure, or infections.

­ Fetal hypoxia, fetal bradycardia, or fetal death may follow as a result of

systemic hypotension.

　

z Establishment of diagnosis of AFE: ~ by a pathologist

Finding in maternal tissue of epithelial squamous cells, lanugo hair, fat

derived from vernix caseosa, mucin derived from infant’s intestinal mucus,

or bile derived from meconium.

z Presumption of diagnosis of AFE:

? Symptoms/signs and their temporal relationship:

Eg. sudden onset of respiratory distress, cardiac collapse, seizures,

unexplained fetal distress, and abnormal bleeding

‚ Clinical conditions associated with AFE:

- Onset of labor

- Rupture of membranes

- Fetal death

- Trauma

- Uterine overdistension by multiple gestation, polyhydramnios, or fetal macrosomia

ƒ Aids for diagnosis of AFE: (see table 2)

z Differential diagnosis of AFE:

z Prompt and aggressive treatment of an acutely ill pregnant patient,

regardless of the cause:

z Medications:

? To maintain systolic blood pressure ³ 90 mmHg, with acceptable

peripheral organ perfusion (manifested by urine output ³ 25 mL/hour)

and to maintain patient’s sensorium:

­ Crystalloids

­ Inotropics (rapid digitalization + b -adrenergics)

­ Pressors (ephedrine, dopamine, dobutamine, norepinephrine infusions)

ø After hypotension has been corrected, fluid therapy should be restricted to

maintenance levels, to minimize pulmonary edema due to developing ARDS.

­ Corticosteroids (hydrocortisone 500 mg iv q6h)

‚ To maintain arterial PO₂ > 60 mmHg or hemoglobin saturation ³ 90%:

­ As in any other conditions when oxygenation and airway patency

may be compromised due to seizures, shock, or severe respiratory

distress, securing an airway through endotracheal intubation is

advisable.

1) Mechanical ventilation and high levels of fractional inspired oxygen (FIO₂)

When still poor oxygenation despite of FIO₂ > 0.6

2) Mechanical ventilation and positive end-expiratory pressure (PEEP)

ƒ To correct coagulation abnormalities:

­ Packed red blood cells

­ Fresh frozen plasma

­ Cryoprecipitates:

- Rich in both fibrinogen and fibronectin, the latter facilitating the uptake of

cellular and particulate debris (such as amniotic fluid contents) from the blood

via the reticuloendothelial system

­ Platelets

­ Oxytocin and other uterotonics for uterine atony

ø The shock seen in these patients is out of proportion to the amount of bleeding,

so vasopressors are an indicated adjunct to blood replacement.

ø If the patient has an epidural catheter, it is prudent to remove it as soon as possible.

However, if bleeding occurs around the device, it may be better to leave it in place

to tamponade the site until further diagnostic testing. After removal of the catheter,

the patient should be monitored closely for any signs of subarachnoid or epidural

hemorrhage.

　

z Data gathered from the National AFE Registry:

- Maternal mortality rate: 61%

z Data from a recently published population-based study from California:

- Maternal survival rate: 73.6%