Question 9 from the first paper of 2016 explored these issues in detail. Specifically, the examiners were most interested in the esoteric topic of peri-mortem caesarian, and much less interested in the rather mundane practice of saving the pregnant cardiac arrest survivor. Also, Question 16 from the first paper of 2010 asked about the modifications to the normal ALS algorithm, but seems to only have expected about three lines. As that question was mainly interested in the physiology of pregnancy, it has been tucked away into the O&G SAQ section. Question 28 from the first paper of 2018 also asked abut the differences in approach to resuscitation of the pregnant patient, and wanted more detail about the factors which might make resuscitation of the pregnant patient more challenging. 

In short,the pregnant patient in cardiac arrest requires several modifications to the cardiac arrest algorithm. These include performing cardiac compressions in a pelvic tilt position, using manual uterine displacement to relieve aortocaval compression, and proceeding quickly to a perimortem caesarian section.

Modifications to advanced and basic life support

The Australian Resuscitation Council was my main resource for these guidelines (see their Guideline 11.10: Resuscitation in Special Circumstances).

Modifications to diagnostic thinking

  • Though pregnant women may die of the same causes as non-pregnant non-women (i.e. the four Hs and four Ts), one needs to keep in mind the following alternative causes of arrest:
    • 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

Issues which complicate the pregnant arrest and peri-arrest scenario

Airway issues

  • Difficult intubation (for various reasons)
  • Increased risk of aspiration
  • Decreased FRC makes respiratory decompensation more rapid, and makes airway access more urgent (though, some might say, the patient has arrested - how much more urgent could it get)

Breathing issues

  • On the list of differentials are amniotic fluid embolism and pulmonary embolism, which are problems with no real immediate reversible solution in the arrest scenario.
  • Oxygen consumption increased
  • Foetal oxygenation needs to be considered
  • If tension pneumothorax is for some reason a serious differential, the chest drains need to be placed higher because of the displacement of the diaphragm by the gravid uterus

Circulatory issues

  • Venous return impaired by gravid uterus
  • Placental arteries are more sensitive to catecholamines, and will constrict when you start giving large boluses of adrenaline
  • Trans-thoracic echocardiography during CPR will be difficult if not impossible, because of the problematic subcostal view

Disability issues

  • If the patient had eclampsia-related seizures and has arrested because of this, it will not be immediately apparent to the rescuers (i.e. the clues may not be obvious, eg. incontinence and a bitten tongue may go unnoticed in the melee of resuscitation)

Performance issues

  • Though it seems an unusual thing to mention specifically as a hindrance to the normal process of resuscitation, the college in their answer to Question 28 from the first paper of 2018 mention "potential for delay/hesitation in delivering indicated treatment e.g. antiarrhythmics, thrombolysis, extracorporeal support due to concerns regarding pregnancy",  which implies that a necessary consideration in resuscitating a pregnant arrest patient is the possibility that your team will refuse to carry out your order to give adrenaline or amiodarone. If your grasp of the reigns of leadership is indeed so tenuous in this arrest, it is unclear why this comment is limited to antiarrhythmics, thrombolysis and ECMO, as the staff would probably not follow any of your other orders either.

Modifications to basic life support

  • Manually displace the uterus to the left (off the aorta and vena cava)
  • Add a left lateral tilt (the ideal angle is unknown, and is thought to be between 15° and 30°)
    • A left lateral tilt may compromise effective CPR, but is still recommended by the ARC Guideline 11.10  (2011) "Special Circumstances". In contrast, ECC and AHA no longer recommend the left lateral tilt (see the 2015 AHA update and the 2015 ECC guidelines). Presumably, once the ARC get around to it, their guidelines will fall in line with international consensus. 
      Question 16 from the first paper of 2010 offers a weirdly specific 27° pelvis tilt. It probably comes from the old AHA guidelines (these days the guideline-makers for the ECC and AHA no longer recommend the left lateral tilt (see the 2015 AHA update and the 2015 ECC guidelines).A left lateral tilt may compromise effective CPR, but is still recommended by the ARC Guideline 11.10  (2011) "Special Circumstances". Presumably, once the ARC get around to it, their guidelines will fall in line with international consensus. The 27° figure comes from Rees and Willis (1998), who got physicians to perform CPR on specially modified mannequins at different degrees of tilt. The authors found that the 27 degrees was the  angle at which safe positioning and compression efficacy were at optimal compromise. Chest compression force was not too badly affected (80% of the force of compressions with the patient in a supine position), and the patient was unlikely to roll off the bed at this angle.
  • Biaxillary defibrillator pad placement may be considered. Anterolateral pad placement requires the lateral pad to go under the breast rather than over it. 
  • Prepare for an emergency perimortem caesarian.

Perimortem Caesarian section

This became a 70%-weighted topic included in Question 9 from the first paper of 2016. An excellent article by Elkady et al (2015) is contemporary to the question, and should act as the main resource. Elkady and colleagues scraped together all the existing case reports and performed an extensive literature review. They lamented the scarcity and poor quality of the literature, which cannot even agree on a satisfactory definition of "perimortem" (is it a better term than "in extremis", or "moribund", or" ante-mortem"?). In celebration of this confusion, these terms (as well as alterative spellings of perimortem and peri-mortem) are used interchangeably throughout this chapter.

Rationale for peri-mortem 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
  • In the case of pregnant cardiac arrest, relief of aortocaval compression is the major modification to BLS/ALS algorithms because aortocaval compression by the gravid uterus is the most significant barrier to successful resuscitation

Arguments for peri-mortem Caesarian

  • Improved venous return to the heart
  • Improved efficiency of external cardiac compressions (in the absence of pelvic tilt)
  • 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.

Arguments against peri-mortem Caesarian

  • Strong evidence in support of perimortem caesarian is lacking.
  • The procedure must occur within 4 minutes of maternal arrest, or the benefit to either mother or foetus is lost. This sort of slick obstetric speed is relatively rare: Katz et al (1986) report on a case series where only 48% of the infants were delivered within this timeframe.
  • The average time from arrest to delivery was 16 minutes in a recent case series of non-trauma arrests (Einav et al, 2012).
  • Of the infants delivered "late", many will have persisting severe neurological sequelae. Katz et al (1986) report that only 66% were neurologicall normal 18 months after delivery.

Theoretical risks of 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, eg. years later an angry father of a disabled child turns up, "why did you do this to my family" etc.; this is particularly concerning in the vacuum of evidence and with only weak support from major society recommendations.
  • Medicolegal risks work in both ways (i.e.one may be determined negligent for not performing this potentially lifesaving procedure).

Evidence regarding the efficacy and safety of  peri-mortem Caesarian

  • An old study (Morris, 1996) reports satisfactory outcomes for both mothers and infants in non-arrest trauma setting (75% survived)
  • In a more modern non-trauma series of perimortem caesarian neonatal survival rate was 62% and a "good" outcome was achieved in half of the survivors.
  • Perimortem caesarian may lead to improved maternal survival and increased rates of ROSC. Beckett et al (2015) found that in all survivors, the median time from arrest to caesarian was shorter than in non-survivors, suggesting that perimortem caesarian has a significant survival benefit.
  • It is true that the recommendations to perform caesarian within 4 minutes of arrest are rarely met, but this does not mean that we should sttop trying to meet them. A rapid and successful perimortem caesarian it is most likely to happen in a large tertiary hospital. Thus, in-hospital arrest is the most important predictor of maternal and foetal survival.

"Own approach"

  • 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
  • Without a prolonged period of maternal haemorrhage or hypoxia
  • With foetal heart beat confirmed as present
  • If there is ample warning to resuscitating staff (eg. advanced notice to the ED), the following measures should take place
    • Neonatologist available on site
    • O&G team scrubbed and ready to meet the patient
    • Brief ABC assessment in the ED to confirm the abovelisted criteria are met
    • Transfer straight to the operating theatre, where the resuscitation may continue
    • If there is no maternal ROSC within 5 minutes, go ahead with the caesarian
    • The caesarian is carried out through a laparotomy midline incision (Elkady et al)
    • If ROSC occurs during the caesarian, one has the option of stopping the delivery and going ahead with normal 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"

References

Einav, Sharon, Nechama Kaufman, and Hen Y. Sela. "Maternal cardiac arrest and perimortem caesarean delivery: evidence or expert-based?." Resuscitation 83.10 (2012): 1191-1200.

Morris Jr, John A., et al. "Infant survival after cesarean section for trauma." Annals of surgery 223.5 (1996): 481.

Beckett, V. A., P. Sharpe, and M. Knight. "CAPS—A UKOSS STUDY OF CARDIAC ARREST IN PREGNANCY AND THE USE OF PERI-MORTEM CAESAREAN SECTION. IMPLICATIONS FOR THE EMERGENCY DEPARTMENT." Emergency Medicine Journal 32.12 (2015): 995-995.

Elkady, A. A. "Peri-mortem Caesarean Section Delivery: A Literature Review and Comprehensive Overview." Enliven: Gynecol Obstet 2.3 (2015): 005.

Campbell, Tabitha A., and Tracy G. Sanson. "Cardiac arrest and pregnancy." Journal of emergencies, trauma, and shock 2.1 (2009): 34.

Katz, Vern L., Deborah J. Dotters, and William Droegemueller. "Perimortem cesarean delivery." Obstetrics & Gynecology 68.4 (1986): 571-576.

Manner, Richard L. "Court-Ordered Surgery for the Protection of a Viable Fetus:, 247 6a. 8b, 274 SE 2d 457 (1981)." (1982).