Amniotic fluid embolism — structured SAQ (15 marks)

(a) Differential diagnosis with the discriminating feature (4 marks)

One mark per diagnosis with its discriminator. A bare list without discriminators scores half. ^[1][2]

Additional credit for naming peripartum cardiomyopathy, aortic dissection, myocardial infarction, sepsis, air embolism or drug error. ^[1]

(b) Immediate management, first five minutes (5 marks)

One mark per point with its reasoning, maximum five. ^[4][6]

• Declare a maternal collapse and activate the maternal cardiac arrest team, allocating airway, compressions, uterine displacement, drugs, scribe and neonatal roles. A protocolised, role-allocated first ten minutes is the intervention with the best evidence in this condition.^[4]
• Airway and 100% oxygen, with early tracheal intubation by the most experienced operator. Hypoxia is what produces the neurological injury that determines outcome.^[6][3]
• If pulseless: CPR flat on a firm surface, hands on the centre of the sternum, with continuous manual left uterine displacement. Drug doses and defibrillation energies are unchanged in pregnancy.^[6]
• Set the clock and perform perimortem caesarean birth by 4 minutes in this undelivered woman at term. It is done in the room, for maternal benefit, because emptying the uterus relieves aortocaval compression.^[6][1]
• Two large-bore cannulae above the diaphragm, bloods including fibrinogen, and activate the massive haemorrhage protocol pre-emptively. The coagulopathy is coming.^[4][5]
• Vasopressors early and fluid cautiously — noradrenaline and vasopressin support the failing right ventricle; large-volume crystalloid distends it and worsens output.^[3]

(c) Haematological management with targets (4 marks)

One mark each for the fibrinogen target and product, the platelet target, the ratio-based plasma and red cell strategy, and one for either tranexamic acid or the factor VIIa caveat. ^[5][1]

• Fibrinogen 0.7 g/L: give cryoprecipitate or fibrinogen concentrate immediately, targeting a fibrinogen at or above 2 g/L. Fibrinogen falls first and fastest in obstetric consumptive coagulopathy.^[5]
• Platelets 62 × 10⁹/L: transfuse to keep platelets above 50 × 10⁹/L, with a higher trigger if she is going to theatre.^[5][1]
• Red cells and fresh frozen plasma in a ratio-based massive transfusion pack until laboratory or viscoelastic guidance is available; use ROTEM or TEG to detect hypofibrinogenaemia and hyperfibrinolysis.^[5][3]
• Tranexamic acid 1 g intravenously over 10 minutes for the haemorrhage component; calcium replacement for the citrate load; active warming throughout.^[1][5]
• Recombinant activated factor VII only as a last resort after full conventional replacement — the systematic review of published cases found worse outcomes in treated women.^[7]

(d) How the diagnosis is confirmed (2 marks)

One mark for stating that it is a clinical diagnosis of exclusion, one for naming the criteria or explaining why no test confirms it. ^[2]

• It is not confirmed by any test. Amniotic fluid embolism is a clinical diagnosis of exclusion made at the bedside. Fetal squames in maternal pulmonary blood are neither sensitive nor specific; tryptase, complement and zinc coproporphyrin are research tools.^[1][2]
• The Clark/SMFM 2016 research criteria define cases for research, not for the bedside: sudden cardiorespiratory arrest, or hypotension with systolic pressure under 90 mmHg plus respiratory compromise; overt disseminated intravascular coagulation documented after the collapse; onset during labour or within 30 minutes of delivery of the placenta; and no fever of 38.0 degrees Celsius or above during labour. All four are required, deliberately trading sensitivity for specificity.^[2]