The patient is a 26-year-old, G1P0, BMI 44, with a medical history including coeliac, depression and anxiety. She took no regular medications as she had ceased her Cymbalta prior to conception. She had an allergy to the measles, mumps and rubella (MMR) vaccine, resulting in reactive arthritis at age ten. Antenatal serology was unremarkable and she had normal glucose tolerance tests. She had an early ultrasound at nine weeks for per vaginal (PV) spotting and low-risk combined first trimester screening. On morphology scan, the heart was not adequately visualised and there was a 4mm choroid plexus cyst in the left ventricle. The placenta was posterior and clear. The patient had a growth scan at 30 weeks, revealing an estimated fetal weight on the 95th percentile and follow-up scan at 34 weeks, with growth on the 88th percentile. Her pregnancy was complicated by multiple antenatal triage assessments for high blood pressure from 30 weeks gestation. She was asymptomatic and her PET bloods were repeatedly normal. At 38+5 weeks, her blood pressure was 148/98. The patient was admitted, commenced on labetalol and an induction of labour was booked.

The patient had a Cervidil inserted at 39+1 weeks and had an artificial rupture of membranes the next day. Syntocinon was commenced, liquor was meconium stained and she was on continuous electrode fetal monitoring. The patient spiked a temperature of 38.6C and was given 2g of Cefazolin. She had an immediate allergic reaction, reporting itchiness all over and a dry, tight mouth. A rapid response call was activated.

The patient received IM adrenalin and began vomiting. Observations at the time were a BP of 120/70, HR 43 and sats at 84 per cent. Concurrently, there was fetal bradycardia. A scalp clip was placed and cervical dilatation was 4cm. A category one caesarean section was called for when the patient stabilised. However, she rapidly deteriorated, losing her airway and then cardiac output. She received IV adrenalin, CPR was commenced and she was intubated. At four minutes of CPR, a perimortem caesarean section was performed. A flat baby was delivered in meconium liquor and given to the paediatric team for resuscitation. Attempts to deliver the placenta were complicated by uterine inversion, which was immediately reverted and the placenta was manually removed. Bimanual compression of the uterus continued during CPR. A total of 14 minutes of CPR was performed and 4mg of adrenalin given. When cardiac output was re-established, she was given morphine, midazolam and vecuronium, and prepared for transfer to theatre.

The patient had very difficult vascular access and had a CVC and arterial line inserted. Haemostasis was achieved with a two-layer uterine closure, ergometrine, PG2Fα and a Bakri balloon. She had a VT arrest with an unsuccessful shock of 100J and a second shock of 200J to return her to sinus rhythm. Her arterial blood gas revealed a potassium of 7 and was treated with 10+10mmol of calcium carbonate, 15 units of actrapid and 50ml of 50 per cent glucose, as well as 25+25mmol of sodium bicarbonate. She was stabilised and transferred to ICU.

In ICU, the patient was intubated, on an adrenalin/noradrenalin infusion and had another PEA/hypotensive arrest, requiring a further five minutes of CPR, adrenalin and calcium gluconate. Issues included a new right bundle branch block on ECG and ECHO showing moderate global impairment of systolic function and low urine output. The patient was hyperkalemic and acidotic, febrile, coagulopathic, and high-risk for aspiration pneumonia and pulmonary embolism.

The patient was extubated and received IV antibiotics, 4xPRBC, 2xFFP and vitamin K. She received three days of dialysis and deep vein thrombosis (DVT) prophylaxis and was discharged from ICU on day ten. Her ward stay was complicated by continued high temperatures and multiple septic work-ups. The only source of infection was a wound on her right forearm from a cannula site, which grew E.coli. This was treated with antibiotics and dressings. She was discharged home on day 17 with cardiology and renal follow up.

The infant, at birth, was pale, floppy and had a heart rate of 40. He received immediate intermittent positive-pressure ventilation (IPPV) and cardiac compressions, which were ceased at 50 seconds of life. He was intubated and had meconium liquor suction from below the cords. His APGARs were 3, 3, 4 and 7 at 1, 5, 10 and 20 minutes of age. He weighed 3.7kg and his arterial gas showed a pH of 6.87, lactate 11.9 and base excess of -20, paired with venous pH 6.89, lactate 12.1 and base excess of -20. NETS were called to arrange transport to NICU. Repeat gas at seven hours of age was pH 7.31, lactate 2.14 and base excess -7. The baby had an uncomplicated admission and was cooled from one hour of age to day three. He had a normal EEG and a head ultrasound showed no intraventricular haemorrhage. The baby was transferred back on day four and discharged home to the care of his father at day five and bottle fed.

Discussion

Cardiopulmonary arrest during pregnancy presents a unique situation that involves potentially two patients, the mother and the fetus, and is associated with high maternal and neonatal mortality rates. The prevalence of cardiac arrest in pregnancy varies from one in 20,000 to one in 50,000 and may be related to conditions that are either unique to pregnancy, or that are found in the non-gravid state.^{1 2} The most common causes of arrest are: pulmonary thromboembolism (PE); haemorrhage; sepsis; peripartum cardiomyopathy; stroke; pre-eclampsia; eclampsia; complications related to anaesthesia; amniotic fluid embolism (AFE); acute myocardial infarction (AMI); pre-existing cardiac disease; and trauma.^{1 2 3} The prevalence of anaphylaxis in pregnancy is estimated at three in 100,000, with antibiotics being the most common trigger.³

Cardiopulmonary arrest requires a rapid multidisciplinary approach, including obstetrics, anaesthetics and paediatrics. BLS and ALS algorithms apply, with some changes necessary to accommodate the anatomical and physiological changes of pregnancy.²

• Airway:
  A difficult intubation needs to be anticipated in a pregnant patient. This case was more challenging, as she was term, obese and anaphylactic. She was also at greater risk of aspiration given she was labouring and not fasted.
• Breathing:
  Ventilation is more difficult secondary to splinting of the diaphragm, as well as the increased oxygen requirements.
• Circulation:
  Aortocaval compression needs to accounted for from 20 weeks gestation with a 15 degree tilt. This can reduce the efficacy of chest compressions.
• Drugs:
  Increased plasma volume results in dilutional anaemia and reduced oxygen-carrying capacity.

Evidence-based practice for the management of an arrest in pregnancy is limited, with most data being drawn from case and cohort studies.^{2 4 5 6} Consensus statements suggest a perimortem caesarean section should begin at four minutes of age, with the fetus delivered by five minutes, and that it is a resuscitative process performed primarily in the interest of the mother.^{2 4 5 6} The aim is to avoid irreversible anoxic brain damage by increasing the effectiveness of the CPR. The emptying of the uterus allows for easier ventilation, more effective cardiac compressions, an increase in circulating blood volume and relief of the aortocaval compression, resulting in a 60–80 per cent increase in cardiac output. Although not a fetocentric measure, a perimortem caesarean section resulting in the delivery of the fetus by five minutes also increases the likelihood of intact fetal survival.^{3 5}

Classically described, a perimortem caesarean section should be a midline incision with a classical uterine incision, however, the operator should use whichever approach they are most comfortable with. Perimortem caesarean section is considered beneficial and in no incidences proved detrimental.⁶

In this case, understanding the principles of maternal collapse and advanced life support in obstetrics allowed for confidence in decision-making to take the urgent action required. Prompt action and great team work were fundamental in the positive outcomes for both mother and baby. A perimortem caesarean section is a rarely encountered and challenging clinical situation, requiring training in the principles of advanced life support and thorough understanding of the role of operative intervention.

1. Lewis G. The Confidential Enquiry into Maternal and Child Health (CEMACH). Saving mothers’ lives: reviewing maternal deaths to make motherhood safer – 2003-2005. The Seventh Report on Confidential Enquiries into Maternal Deaths in the United Kingdom. London: CEMACH. 2007.
2. Suresh MS, LaToya Mason C, Munnur U. Cardiopulmonary resuscitation and the parturient. Best Pract Res Clin Obstet Gynaecol. 2010; 24:383.
3. Mhyre JM, Tsen LC, Einav S, et al. Caridac arrest during hospitalisation for delivery in the United States, 1998-2011. Anesthesiology. 2014; 120:810.
4. Mhyre JM, Tsen LC, Einav S, et al. Cardiac arrest during hospitalisation for delivery in the United States, 1998-2011. Anesthesiology. 2014; 120:810.
5. Rose CH, Faksh A, Traynor KD, et al. Challenging the 4 to 5 minute rule: from perimortem caesarean to resuscitative hysterotomy. AJOG. 2015; 653-656.
6. Einav S, Kaufman N, Sela HY. Maternal cardiac arrest and perimortem caesarean delivery: evidence-based or expert opinion? Resuscitation. 2012;83:1191-200.