Viva 1

You have been called to an emergency on the obstetric ward. The patient is a 32-year-old  female who has been in hospital for 4 days for management of hypertension during labour (at 37 weeks). She had just undergone induction of labour, planning for normal vaginal delivery. She has become acutely breathless, lost consciousness, and has no palpable pulse. 

What are the main differential diagnoses and how would you distinguish between them?

Originally, the CICM paper said that "This viva dealt with the management of asthma in pregnancy." The text has been altered to add cardiac arrest, and to remove the asthma. 

Main differentials would have to include:

  • Standard 4 Hs and 4 Ts:
    • Hypoxia 
    • Hypovolemia 
    • Hyper/hypokalemia 
    • Hyper/hypothermia 
    • Tension pneumothorax 
    • Tamponade 
    • Toxins 
    • Thrombus 
  • Additional possibilities because of the hypertensive pregnancy:
    • Amniotic fluid embolism
    • Hypertensive disorder of pregnancy (with ensuing cardiac failure)
    • Seizures (with ensuing hypoxia and arrest)
    • Haemorrhage from liver rupture
    • Haemorrhage from uterine rupture

If they need to be redirected:

What findings would help discriminate between these differentials?
  • Massive PE (distended neck veins, cyanosis, tachycardia and hypotension)
  • Tension pneumothorax (unequal air entry, deviated trachea, unilaterally hyper-resonant chest)
  • Massive haemothorax or effusion (unequal air entry, deviated trachea, dull percussion note over the hemithorax)
  • Pulmonary oedema (pink frothy sputum, coarse gurgling creps)
  • Extremes of hypovolemia (collapsed veins, empty chambers, slow capillary refill, dry mucosae, cool extremities, weak rapid pulse)
  • Haemorrhagic shock ( exactly as above but also deathly pallor)
  • Cardiac tamponade (distended neck veins, muffled heart sounds, electrical alternans on ECG)
  • Peri-arrest arrhythmia (eg. VT or SVT on monitor)
  • Severe sepsis (mottled skin, fever, hyperdynamic circulation with hypotension)
The ward staff have commenced CPR. What specific instructions will you give them?

If you need to reword this question, you could also ask: "what modifications to the normal ALS algorithm are required in pregnancy?"

  • Manually displace the uterus to the left (off the aorta and vena cava)
    • The 2015 AHA guidelines recommend this, instead of a 15° and 30° tilt (as the tilt can decrease the efficiency of chest compressions).
    • The 2021 ESC guidelines still recommend a lateral tilt.
    • ARC guidelines date back to 2011, so who cares what they think.
  • Biaxillary defibrillator pad placement may be necessary. Anterolateral pad placement requires the lateral pad to go under the breast rather than over it. 
  • Prepare for an emergency perimortem caesarian.
The rhythm is PEA. How does this narrow the range of possibilities?
  • PEA is more often the consequence of some sort of restriction on either preload or afterload (i.e. an empty heart pumping) - for instance, obstructive shock, or massive hypovolemia.
  • Dynamic hyperinflation, amniotic fluid embolism, PE and haemorrhage become more likely
What are the clinical features which could help distinguish amniotic fluid embolism from other causes of cardiac arrest?

Physical examination findings:

  • Severe hypoxia
  • PE-like VQ mismatch
  • Cardiogenic pulmonary oedema, plus non-cardiogenic "capillary leak" oedema
  • Bronchospasm (similar mechanism to anaphylaxis)
  • Petechii

For a conscious patient, a history of:

  • Chills, nausea, vomiting, agitation
  • Coma or seizures
  • Foetal distress

TTE findings:

  • Dilated right heart
  • Features of right heart pressure overload and right heart strain
  • Generally, resembles massive PE
How would you make the diagnosis of amniotic fluid embolism?
  • This is usually a diagnosis of exclusion and based on strong clinical suspicion.
  • Bloods:
    • FBC (thrombocytopenia)
    • Coags/fibrinogen (DIC)
    • Troponin (cardiac strain)
    • ABG (hypoxia, lactic acidosis)
  • Imaging etc:
    • TTE/TOE (right heart strain, evidence of obstructive shock)
    • ECG (RV strain)
    • CXR (pulmonary oedema)

Viva candidates are unlikely to know these details, but in case they spontaneously come up with this stuff, they should get full marks, and a puppy.

  • Gold standard of diagnosis is the totally unrealistic manoeuvre of sucking some amniotic fluid debris out of a distal port of the PA catheter. 
  • Foetal debris in maternal sputum  is a more civilised alternative, but again unlikely to be game-changing if you already strongly suspect AFE.
  • Foetal antigen serology looking for TKH-2 antibodies ( or insulin-like growth factor binding protein-1) are apparently not well validated.
What are the risk factors for amniotic fluid embolism?
  • Precipitous or tumultuous labour.
  • Advanced maternal age.
  • Caesarean and instrumental delivery.
  • Placenta previa and abruption.
  • Grand multi-parity (≥5 live births or stillbirths), 
  • Cervical lacerations.
  • Foetal distress.
  • Eclampsia, or any sort of hypertensive disorder of pregnancy
  • Medical induction of labour.
  • Polyhydramnios
What are the criteria for considering a perimortem caesarian section?
  • Patient meeting criteria for perimortem caesarian
    • Less than 4-5 minutes from arrest
    • Without a prolonged period of unwitnessed collapse
    • At or after 23 weeks of gestation
  • If the delivery is being performed with foetal survival as the rationale, further criteria apply:
    • Without a prolonged period of maternal haemorrhage or hypoxia
    • With foetal heart beat confirmed as present
What is the rationale for a perimortem caesarian?
  • The practice is recommended for pregnancies later than the 23rd week (fundal height more than 2 finger breadths above the umbilicus), because:
    • A foetus beyond the 23rd week has a chance of extrauterine survival  
    • A gravid uterus beyond the 23rd week is large enough to cause aortocaval compression
    • Aortocaval compression by the gravid uterus is the most significant barrier to successful resuscitation
    • The priority is maternal survival. If maternal survival is impossible, there should be no delay in ensuring foetal survival. As the college put it, "There is no requirement for transfer to an operating theatre, obstetric/surgical expertise, and equipment beyond a scalpel or lengthy antiseptic procedures"
    • In the presence of truly unsalvageable maternal pathology, it offers a chance for foetal survival
    • Delivery of the foetus and placenta allows ample space in the abdomen for transabdominal direct cardiac massage to take place.
What are the theoretical risks of a perimortem caesarian?
  • Foetal injury during the rushed procedure
  • Maternal complications consistent with survival, but resulting in disability (eg. ranging from loss of fertility to bowel perforation, infection, paraplegia etc)
  • Medicolegal risks, which work in both ways (i.e.one may be determined negligent for not performing this potentially lifesaving procedure).
An O&G registrar carries out an emergency caesarian through a laparotomy midline incision at 10 minutes. Maternal ROSC is achieved. 
The patient remains haemodynamically unstable, with evidence of severe right heart strain on TOE. What will your ongoing management consist of?

This is an optional question to mop up extra marks, if the candidate did really well, or really badly (i.e. skipped all the other questions)

Specific management:

  • Maintain normoxia.
    • Ventilate with 100% FiO2
    • Ensure adequate filling to improve shunt fraction
    •  
  • Encourage pulmonary arterial vasodilation:
    • Inhaled nitric oxide
    • Inhaled prostacycline
  • Maintain satisfactory cardiac output
    • Inotropes and vasopressors
    • IABP
    • VA ECMO
  • Consider decontaminating the circulation
    • CVVHDF to clear out the circulating proinflammatory foetus chunks
      (Kaneko et al, 2001)
    • Plasma exchange, which frequently happens in an uncontrolled manner as the patient tries to bleed to death and receives a massive transfusion "in exchange"(Awad et al,  2001).
    • Cell salvage and blood filtration may work. Water et al (2000) reported a case where much of the foetal debris was removed from the blood by a cell saver device.

Supportive management:

  • Attention to electrolytes to ensure ionised calcium is well corrected
  • Aggressive fluid resuscitation to account for third-space losses (leaky capillaries)
  • Activated Factor VIIa for DIC-induced haemorrhagic complications (Lim et al, 2004)

Disclaimer: the viva stem above may be an original CICM stem, acquired from their publicly available past papers. Or, perhaps it is a slightly altered version of the original CICM stem. Or, it is a completely original viva stem, concocted by the monstrously amoral author of Deranged Physiology for nothing more than his own personal amusement. In either case, because the college do not make the main viva text or marking criteria available, almost everything here has been confabulated. It might sound like a plausible viva and it could be used for the purpose of practice, but all should be aware that it does not represent the "true" canonical CICM viva station. 

References

Jeejeebhoy, Farida M., et al. "Cardiac arrest in pregnancy: a scientific statement from the American Heart Association." Circulation 132.18 (2015): 1747-1773.

Lott, Carsten, et al. "European resuscitation council guidelines 2021: cardiac arrest in special circumstances." Resuscitation (2021).

Lim, Y., et al. "Recombinant factor VIIa after amniotic fluid embolism and disseminated intravascular coagulopathy." International Journal of Gynecology & Obstetrics 87.2 (2004): 178-179.

Davies, Sharon. "Amniotic fluid embolism and isolated disseminated intravascular coagulation." Canadian Journal of Anesthesia 46.5 (1999): 456-459.

Kaneko, Yuhko, et al. "Continuous Hemodiafiltration for Disseminated Intrav ascular Coagulation and Shock due to Amniotic Fluid Embolism: Report of a Dramatic Response." Internal medicine 40.9 (2001): 945-947.

Awad, I. T., and G. D. Shorten. "Amniotic fluid embolism and isolated coagulopathy: atypical presentation of amniotic fluid embolism." European journal of anaesthesiology 18.6 (2001): 410-413.

Waters, Jonathan H., et al. "Amniotic fluid removal during cell salvage in the cesarean section patient.The Journal of the American Society of Anesthesiologists 92.6 (2000): 1531-1536.

Knight, Marian, et al. "Incidence and risk factors for amniotic-fluid embolism."Obstetrics & Gynecology 115.5 (2010): 910-917.

Knight, Marian, et al. "Amniotic fluid embolism incidence, risk factors and outcomes: a review and recommendations." BMC pregnancy and childbirth12.1 (2012): 7.