2.3 Amniotic Fluid Air Embolism

Question 1

A 37-year-old female who is 30 minute postpartum with an epidural
suddenly becomes short of breath and is worsening.

What are the causes of shortness of breath in pregnancy?

Answer 1

Patient factors
* Asthma
* Pulmonary infection
* Anaemia

Obstetric factors
* Pre-eclampsia
* Amniotic fluid embolism (AFE)
* Pulmonary embolism
* Ergometrine use
* Cardiomyopathy

Anaesthetic factors
* High block assuming that the epidural is still being used in this case

Another way to classify the differential diagnoses is to take the obstetric
versus nonobstetric approach.

Question 2

What is the pathophysiology of AFE?

Answer 2

First described by Steiner in 1941,

it is a diagnosis of elimination after other causes of
cardiovascular instability and collapse have been rejected.

Difficult diagnosis is reflected by a wide ranging incidence of
1:8000 to 1:80 000 deliveries

Question 3

Pathogenesis

Answer 3

1. • Embolic:
     due to an emboli caused by entry of
     amniotic fluid or fetal cells in the circulation
2. • Immunological:
     similar to anaphylaxis as fetal cells are not always present

Question 4

Presentation

Answer 4

• Occurs usually during labour and delivery
  (including LSCS) but can occur
  up to 48 hours post delivery, typically in two phases
  .
• Phase 1:
  characterised by acute shortness of breath and hypotension
  followed by cardiac failure,
  cardiac arrest,
  pulmonary oedema,
  acute lung injury, convulsions. and loss of consciousness.
  The maternal mortality rate is 26%–60%.
• Phase 2: 40% of women who survived the first stage will go on to develop
  the haemorrhagic phase due to DIC.

Question 5

What are the risk factors for AFE?

Answer 5

No proven risk factors,
but the following may be associated with a higher risk
of developing AFE:

Advanced maternal age,
multiparity,
meconium stained liquor,
intrauterine fetal death,
polyhydramnios,
strong frequent or tetanic uterine contractions,
microsomia,
chorioamnionitis,
uterine rupture,
and placenta accreta.

Question 6

What systemic changes occur during AFE?

Answer 6

1. Haemodynamic changes
   * Increase in systemic and pulmonary vascular resistance,
   resulting in acute pulmonary hypertension,
   left ventricular dysfunction and pulmonary oedema.

• Myocardial dysfunction results from ischaemia
  and as a direct depressant
  effect of endothelin and humoral factors.

2. Pulmonary
   * Vasospasm and ventricular dysfunction lead to hypoxia.

• Survivors develop an ARDS-like picture.

3. Coagulation.

• DIC
• Amniotic fluid contains activated coagulation factors II, VII, and X. It
  induces platelet aggregation, releases platelet factor III, and has a
  thromboplastin-like effect.
• The clinical picture is one of massive haemorrhage and haemodynamic
  collapse.

Question 7

What is the management of AFE?

Answer 7

The management is mainly supportive,
invasive monitoring,
and transfer to ITU.

Management goals in the operating theatre are

• Maintaining oxygenation—use of PEEP.
• Haemodynamic stability—inotropes are usually required.
• Maintenance of uterine tone.
• Management of DIC—
  Liaise with haematologist. FFP, cryoprecipitate, and
  platelets are usually required.
  Recombinant factor VII has been used in
  massive haemorrhage.