Peripartum extracorporeal life support

Learning objectives.

By reading this article you should be able to:

• •Describe the common indications and outcomes (maternal, neonatal) of extracorporeal life support (ECLS) in the peripartum period.
• •Explain the importance of extracorporeal membrane oxygenation (ECMO) consultants in high-risk peripartum patients.
• •Compare the management of ECMO in peripartum and non-peripartum patients

Key points.

• •The use of peripartum ECMO including ECPR has increased dramatically over the last two decades.
• •Peripartum ECMO patients are best cared for by a multidisciplinary team.
• •The physiological changes of pregnancy dictate different physiological targets during ECMO support.
• •Obstetric patients have better outcomes with ECLS compared with other groups of patients.
• •Management of maternal cardiac arrest should include early activation of potential ECPR.

Maternal morbidity and mortality

During the last two decades, healthcare outcomes have improved for patients with congenital conditions with increasing numbers surviving into adulthood, more patients living with chronic medical conditions and most recently, a global respiratory pandemic with coronavirus disease (COVID-19). These trends are reflected in the obstetric population worldwide with increasing maternal morbidity and are relevant for the consideration of advanced therapies including extracorporeal life support (ECLS). The leading cause of maternal death in the USA and the UK is cardiovascular disease and the most recent maternal mortality report from the Centers for Disease Control and Prevention demonstrates that the rate has increased in 2022 to 32.9 deaths per 100,000 live births compared with 23.8 in 2020.¹ The Confidential Enquiries into Maternal Deaths and Morbidity in the United Kingdom and Ireland also noted an increase in the maternal mortality rate with a rate of 10.9 deaths per 100,000 live births during the period of 2018–20 compared with 8.9 from 2017–19.² Given this trend of rising maternal morbidity and mortality, there is an increasing need for treatment of life-threatening pathology including cardiomyopathy, acute heart failure, thromboembolism and respiratory failure.

Extracorporeal life support

Extracorporeal life support has been increasingly used as a rescue therapy in acute respiratory distress syndrome (ARDS) and cardiovascular decompensation in adults. Extracorporeal membrane oxygenation (ECMO) can be used in various configurations depending on the need for respiratory or cardiac support. Venovenous (VV) and venoarterial (VA) configurations support respiratory failure and cardiac or combined cardiorespiratory failure, respectively. Combined configurations are also used as needed for certain instances of mixed cardiorespiratory support.

Indications for respiratory ECMO (most commonly VV) include ARDS; as a bridge to lung transplantation; primary graft dysfunction after lung transplantation; chronic obstructive lung disease; and asthma. Cardiac ECMO (most commonly VA) is indicated for acute myocardial infarction; cardiomyopathy; shock after cardiotomy; septic shock; hypertension; bridge to heart transplant; primary graft dysfunction after heart transplantation; blunt cardiac injury; massive pulmonary embolism; intoxications; and arrhythmias. Extracorporeal cardiopulmonary resuscitation, or ECPR, is used in the context of cardiac arrest with ongoing chest compressions (or inability to achieve sustained return of spontaneous circulation for at least 20 min) to restore systemic perfusion. Table 1 lists the most commonly reported aetiologies for ECMO in the pregnant and peripartum population.

Table 1.

Summary of the most common current indications for pulmonary and cardiac ECLS.

Pulmonary	Cardiac
•Acute respiratory distress syndrome •Asthma •Hypertensive disorders of pregnancy •Fluid overload •Pulmonary embolism •Cardiac disease •Pneumonia •Aspiration •Pulmonary haemorrhage •Sepsis	•Cardiac arrest •Heart failure •Peripartum cardiomyopathy •Septic cardiomyopathy •Pulmonary embolism •Amniotic fluid embolism •Pulmonary arterial hypertension

Table 2.

Monitoring and technical considerations in pregnant and non-pregnant patients. MFM, Maternal Fetal Medicine.

Monitoring

•Arterial catheter: upper extremity, right-sided if femoral or left axillary VA ECMO. •Central venous catheter: ideally above the diaphragm. •Fetal heart monitoring: daily or continuous depending on gestational age, MFM and institutional recommendations. •Uterine tocodynamometry: assessment for uterine contractions based on clinical scenario.

Technical issues

•Aortocaval compression from gravid uterus (>20 weeks of gestation)—consider uterine displacement 15–30° for cannulation and to maintain adequate flow. •Pao2 goal ≥9.5 kPa for fetal perfusion. •Paco2 goal 4.0–4.3 kPa for fetal acidosis.

Delivery considerations

• Gestational age: ○ Before viability and 28 weeks: no evidence that termination of pregnancy will improve maternal outcomes. ○ 28–32 weeks: the mechanical respiratory changes of pregnancy and fetal oxygen consumption may increase burden on maternal oxygenation. There is some evidence that delivery may improve Pao2 and airway pressures in pregnant patients with ARDS. However, it does not reduce duration of mechanical ventilation or need for ECMO. ○ Beyond 32 weeks: the fetal risk and maternal benefit of delivery is supported by expert consensus and if safe and feasible, may be pursued. • Method of delivery: no data to support one mode over another in these patients ○ Vaginal/assisted vaginal/Caesarean. ○ Prior obstetric history and cervical examination taken into account for potential induction of labour. ○ Greater risk of haemorrhage with Caesarean delivery.

Trends of peripartum ECLS

Extracorporeal membrane oxygenation is increasingly being used in obstetric patients. A systematic review in 2020 demonstrated an exponential increase in reporting across the years studied from 1974 through 2019 with an inflection point in 2009 at the time of the H1N1 influenza pandemic that disproportionately affected pregnant women.³ Another study reporting the use of ECMO in pregnancy using the National Inpatient Sample found more than 300 cases between the years of 1999 and 2014 and showed a 145% increase in the use of ECMO for every 4-year period studied.⁴ Data from the Extracorporeal Life Support Organization (ELSO) registry including 88 women who required VA ECMO for peripartum cardiomyopathy showed that the rate of use has risen dramatically from 2007 to 2019 and that this has coincided with an increased rate of maternal survival.⁵

Considerations relating to pregnancy

Physiological changes of pregnancy

Important physiological changes of pregnancy across multiple organ systems that are relevant when caring for a parturient on ECMO are summarised in Figure 1.

Fig 1.

Specific considerations for ECMO in the peripartum patient. BBB, blood brain barrier; BP, blood pressure; BV, blood volume; CBF, cerebral blood flow; CC, closing capacity; CO, cardiac output; CrCl, creatinine clearance; CVP, central venous pressure; HR, heart rate; MV, minute ventilation; EF, ejection fraction; ERV, expiratory residual volume; FEV1, forced expiratory volume in 1 s; FEV1/FVC, ratio of FEV1 to FVC; FRC, functional residual capacity; FVC, forced vital capacity; GFR, glomerular filtration rate; HCO3, bicarbonate; IC, inspiratory capacity; LUD, left uterine displacement; LVEDV, left ventricular end diastolic volume; Paco₂, arterial partial pressure of carbon dioxide; Pao₂, arterial partial pressure of oxygen; PCWP, pulmonary capillary wedge pressure; PV, plasma volume; PVR, pulmonary vascular resistance; RBC, red blood cell; RBF, renal blood flow; SNS, sympathetic nervous system; SV, stroke volume; SVR, systemic vascular resistance; TV, tidal volume; VC, vital capacity; Vo₂, oxygen consumption; WBC, white blood cell.

Cardiovascular changes and haemodynamic considerations

The cardiovascular changes of pregnancy are secondary to an increase in serum relaxin, progesterone, oestrogen, renin, aldosterone and adrenomedullin, resulting in an overall increase in vasodilation, cardiovascular compliance and capacitance.⁶ Oxygen demand increases secondary to the metabolic needs of the mother and fetus, met by an increase in cardiac output. The increased cardiac output begins early in gestation, up to 50% at 12 weeks and 150% of non-pregnant values immediately after delivery.⁶ This increase is primarily driven by an increase in end-diastolic volume, resulting in an increased stroke volume, and by a modest increase in heart rate.⁷ The increase in cardiac output may require higher ECMO flows to support systemic oxygenation and the use of larger sized cannulae. Earlier delivery, such as immediately after ECMO cannulation and initiation, may also relieve some of the need for increased flow. Peripheral vascular resistance decreases by 30% with lowest values in the second trimester, secondary to various hormonal changes including increased serum relaxin, progesterone, oestrogen and nitric oxide.⁷

Beyond 20 weeks of gestation, the gravid uterus may cause aortocaval compression in the supine position. This may lead to haemodynamic compromise and the use of left lateral position with 15–30° tilt to relieve this mechanical obstruction is recommended to maintain uteroplacental flow.⁸ Pregnant patients may be challenging to cannulate for ECLS because of inferior vena caval compression, and left lateral tilt may facilitate passage of the wire and the cannulae in patients beyond 20 weeks of gestation.⁸ Although not evidence-based in the ECMO, left-sided tilt may also improve venous drainage and arterial outflow in obstetric patients supported by ECMO and should be considered when difficulty maintaining adequate circuit blood flow is encountered.

Cardiovascular demand is highest in the hours after delivery, which corresponds to an autotransfusion with removal of the low-resistance placenta and relief of vena caval compression. This is the highest risk period for patients with cardiac disease or obstructive physiology who may decompensate secondary to acute right, left, or biventricular heart failure with this functional fluid shift and increasing systemic vascular resistance. Close monitoring during this period is imperative to promptly deploy VA-ECMO support if needed in high-risk patients.

Pulmonary changes and ventilatory considerations

Progesterone is a strong respiratory stimulant that drives the increase in minute ventilation and the hypoxic respiratory drive; oestrogen also affects the hypoxic ventilatory response and contributes to upper airway changes that result in oedema and tissue friability.⁹

Throughout the course of pregnancy, changes in the chest wall compensate for the upward displacement of the diaphragm resulting in an overall increased tidal volume by up to 40% of pre-pregnancy values and a compensated respiratory alkalosis.⁹ During pregnancy, Paco₂ ranges between 3.8 and 4.2 kPa (28–32 mmHg) and a Pao₂ between 13.3 and 14.0 kPa (100–105 mmHg).⁹ Functional residual capacity, inspiratory reserve and residual volumes are reduced in pregnancy and, coupled with increased oxygen consumption, result in poor tolerance of hypoxaemia in the parturient. Airway management in the obstetric patient carries substantially higher risk than in non-pregnant patients, with a greater risk of encountering a difficult intubation as a result of airway swelling, difficult laryngoscopy, large breasts, airway trauma and emergency situations.⁹

These physiological changes affect the oxygenation goals for a pregnant patient undergoing ECMO support and the decision to cannulate for respiratory indications. In non-pregnant patients, the criteria used to initiate ECMO are typically institution-dependent and account for the clinical trajectory. In addition, many centres base their decision on criteria described in the EOLIA trial.¹⁰ These cut-offs include: (i) P:F ratio <80 mmHg for > 6 h or (ii) P:F <50 mmHg for >3 h or (iii) arterial pH <7.25 with Paco₂ at least 8.0 kPa (60 mmHg) for 6 h despite a ventilatory frequency of 35 and plateau pressure no more than 32 cmH₂O.¹⁰ Of note, this trial excluded pregnant women. The exclusion of pregnant patients is an important caveat as it is likely the criteria selected in the EOLIA trial would result in fetal compromise and be harmful to the underlying physiological needs of the pregnant woman. In the absence of consensus guidelines, it may be appropriate to use slightly more liberal criteria in pregnant patients in order to improve oxygen delivery to the fetus in distress and continue the pregnancy to a gestational age >28 weeks.¹¹

Oxygenation goals are aimed at optimising fetal oxygen delivery because maternal hypoxia is associated with placental vasoconstriction secondary to hypotension, uterine contractions, acidosis, alkalosis, or both.⁹ It is recommended that normal oxygenation or a Pao₂ at least 9.3 kPa (70 mmHg) is maintained in the pregnant patient on ECMO to ensure adequate fetal oxygenation and support normal fetal acid–base status. However, this recommendation is based on expert opinion, rather than evidence from clinical studies. Ventilation goals are to maintain normal Paco₂ during pregnancy, which can be achieved through sweep gas titration in order to avoid hyper- or hypocapnia and subsequent uterine artery vasoconstriction.⁹ Permissive hypercapnia has not been shown to be harmful in pregnancy with Paco₂ <8 kPa (<60 mmHg). However, the goal is to aim for normal maternal pH and Paco₂ targets within range for pregnancy.⁹ Importantly, Paco₂ changes (>50% reductions) within the first (approximately) 24 h of starting ECMO have been associated with an increased risk of neurological complications.¹²

Haematological changes and anticoagulation

The increased blood volume during pregnancy is secondary to a relatively greater expansion of plasma to red blood cell volume resulting in a relative anaemia of pregnancy. Fibrinogen, ferritin, factors VII and VIII, and von Willebrand factors increase and protein S concentrations decrease as pregnancy progresses resulting in an overall hypercoagulable state by term.¹³ Gestational thrombocytopenia may be noted secondary to haemodilution and platelet activation.¹³

The haematological changes during pregnancy result in hypercoagulability and the bulk of the literature describing ECMO in pregnancy reports the use of anticoagulation.^3,14,15 Conventional activated partial thromboplastin time (aPTT) and anti-Xa values used in general patients receiving ECMO may be used for those in the peripartum period.¹⁶ Unfractionated heparin does not cross the placenta and is typically used as the first line for anticoagulant in peripartum ECMO. There is limited literature (case reports) on the use of direct thrombin inhibitors during pregnancy.^14,15 Although it is ideal to use anticoagulation in ECMO, it is not required so long as blood flow rates are acceptable (e.g. >3 L min⁻¹). Stopping or reducing the degree of anticoagulation at the time of Caesarean delivery may facilitate haemostasis. Although anticoagulation for ECMO is ideal, stopping anticoagulation, or completely anticoagulation-free support is possible with acceptable risks of thrombosis for the patient and ECMO circuit. There are multiple case series of stopping or complete lack of anticoagulation in various groups, including in patients with bleeding, undergoing procedures and acute trauma.17, 18, 19, 20

Pregnant patients may require delivery during ECMO which complicates the practice of withholding anticoagulation for vaginal delivery, Caesarean delivery, or both. The newest generations of heparin-coated circuits have a reduced need for anticoagulation and may be useful, as these patients have an increased risk of bleeding around delivery and a general risk of thrombosis. A backup circuit and cannulation supplies should be available in case of circuit thrombosis, other malfunction, or both.

Fetal considerations

Fetal monitoring is performed using the fetal heart rate (FHR) tracing to assess for rate, variability, accelerations and decelerations and be used as a marker of fetal well-being. Fetal distress, acidaemia, or both are associated with heart rate decelerations that suggest uteroplacental insufficiency.

Obstetric patients supported by ECMO may undergo FHR monitoring driven by the recommendations of the maternal fetal medicine team which may vary between individual providers and institutions. Generally, pregnant patients supported by ECMO beyond 22 weeks of gestation should undergo some form of monitoring: daily, multiple times a day, or continuous. Fetal heart rate monitoring is recommended when an intervention would be considered for a non-reassuring tracing. This raises several important questions for decision-making including the maternal wishes for prolonging the pregnancy vs delivery. Another important ethical question in FHR monitoring is whether the mother is stable enough to undergo delivery safely in the setting of fetal distress.

Fortunately, interventions that benefit maternal haemodynamics generally also improve the fetal environment. Adequate resuscitation to the mother may be reflected in improvement in the FHR tracing. In addition to maternal support, ECMO variables, medications, or both may be titrated to improve arterial blood pressure (with increased blood flows in a VA ECMO strategy), oxygenation (with changes in fraction of delivered oxygen from the oxygenator) and ventilation (with changes in sweep gas flow) to optimise fetal status.

Obstetric considerations

Method and timing of delivery

The method of delivery should be dictated by obstetric indications. Vaginal, operative vaginal and Caesarean deliveries have all been described in peripartum patients receiving ECMO.^3,14,15 Compared with vaginal delivery, Caesarean section has an increased risk of haemorrhage and venous thromboembolism (VTE), and therefore should be reserved for obstetric indications.²¹ The decision to deliver a pregnant patient on ECMO is assessed on a case-by-case basis as there are no guidelines regarding the optimal gestational age or timing. The expert consensus is that delivery of the fetus for respiratory distress is unlikely to result in substantial pulmonary benefit to the mother before 32 weeks of gestation and contributes to iatrogenic prematurity and risk of haemodynamic fluctuations in the mother at a time of vulnerability in critical illness. The cardiovascular stress associated with delivery and risk of infection, bleeding, and preterm birth must be balanced against the potential maternal and neonatal benefit. Prolonging the pregnancy is generally recommended up to 30–32 weeks to reduce the complications associated with preterm neonates and delivery before this time is unlikely to confer respiratory benefit to the mother. Beyond 32 weeks, a controlled and well-coordinated delivery may be considered to facilitate ongoing maternal care.

Although one study that examined pregnant patients with severe COVID-19 infection demonstrated that delivery at an average gestational age of 31 weeks was associated with modest improvements in ventilator variables, including driving pressure and P:F ratios, this was not associated with clinical outcome improvements.²² There is not a defined gestational age cut-off for cannulation vs delivery and all patients should be considered uniquely, taking into account maternal comorbidities, clinical trajectory and fetal status.

Delivery equipment should be available at the bedside of any patient who remains pregnant on ECMO. A clear communication plan should be in place for the teams caring for these patients to reduce potential maternal morbidity, neonatal morbidity, or both in the event of an urgent or emergent need for delivery. The location of delivery is dependent on the institution; teams should include physicians and nurses who are familiar with operating on and anaesthetising pregnant patients with the flexibility to adapt to the complexities of ECMO. Obstetric and cardiac anaesthesiologists may work together in a team to best address the unique needs of these patients including anaesthetic medications, vasopressors, inotropes, uterotonics, surgical procedures/interventions, ECMO physiology and transoesophageal, transthoracic, or both echocardiography. Table 2 summarises specific considerations for monitoring and technical aspects of care in this unique population.

Team composition

The complexity of obstetric patients who require ECMO demands a multidisciplinary team including physicians and nursing from intensive care, maternal fetal medicine, neonatology, obstetric anaesthesiology, cardiac anaesthesiology, cardiac surgery and pharmacy. Experienced ECMO centres should have a dedicated ECMO team including ECMO specialists with 24-h presence who, in conjunction with the ICU team, ensure adequate therapy equipment function and monitor for complications. Additional consultation from cardiology, haematology, pulmonology, infectious disease, radiology, surgical specialties and beyond are frequently indicated.

Intraoperative considerations

Anaesthetic technique

Neuraxial anaesthesia is very rarely used given the heightened risk of neurologically relevant bleeding because of acquired circuit coagulopathy (qualitative large von Willebrand factor deficiency, factor consumption and thrombocytopenia) and the concurrent use of anticoagulation, although it has been described.¹¹ In patients without a secure airway, vaginal delivery is possible, although pushing can result in acute decreases in circuit flows from varying intra-abdominal and intrathoracic pressures in addition to the position changes that could compress ECMO cannulae. This may be mitigated by the use of an assisted second stage delivery with forceps, vacuum delivery, or both. Caesarean section with general anaesthesia is the most frequently described mode of delivery although it is accompanied by the highest likelihood of blood loss, which can also result in acute changes in ECMO circuit blood flow. In order to decrease the risk of ECMO circuit flow issues, hypovolaemia should ideally be pre-emptively corrected and left uterine displacement should be performed prophylactically.

Medications

In patients undergoing general anaesthesia, inhaled anaesthetics are not the ideal agents in either VV or VA ECMO. In VV ECMO, low tidal volumes and significant lung pathology can impede delivery of anaesthetic agents to the bloodstream resulting in unreliable anesthesia.²³ In VA ECMO, significant portions of the total blood volume are diverted away from the lungs, further making adequate absorption of these agents into the blood unreliable.²³ The most straightforward method of anaesthetising patients undergoing ECMO is using intravenous agents, which also obviates the need for changing to different sedative agents when the procedure is completed.

Knowledge of the effect of the ECMO circuit on anaesthetics and other medications is limited, but all medications have been used to achieve the desired levels of anaesthesia and analgesia. In general, anaesthetists should use the medications with which they are most comfortable, with consideration that they may need to increase dose and give doses more slowly to avoid vasodilation and ECMO circuit suction events. The volume of distribution and potential for drug sequestration are greater in patients supported by ECMO and thus higher than expected doses may be needed to achieve amnestic effect.²³ Minimising fetal drug exposure is also important. The use of processed electroencephalography monitoring for depth of anaesthesia may be appropriate to optimally titrate anaesthesia.

Uterotonic medications may be given for uterine atony. Oxytocin, which is the first-line agent for haemorrhage, may be used as an i.v. infusion or i.m. injection with attention to the volume with which it may be administered. Second-line medications include ergot alkaloids, which may increase afterload, and prostaglandin F2α, which may cause bronchospasm. These agents should be given with thoughtful consideration of the risks and benefit for uterine tone. Adjustment to flows and use of vasodilators, bronchodilators, or both may mitigate the potential adverse effects of these medications.

Tranexamic acid may be considered in the context of haemorrhage, hyperfibrinolysis, or both as it has been shown to reduce death in obstetric patients from bleeding and in patients on ECMO.^24,25

Blood transfusion

The blood bank should be contacted as soon as a procedure is planned, and adequate blood products (6 units of RBCs, 4–6 units FFP, cryoprecipitate, platelets) should be in the operating room ideally before incision in preparation for potential large volume resuscitation. In the case of truly emergent surgery, a massive transfusion protocol may be necessary to mobilise blood products in a sufficiently timely manner.

Outcomes

Survival

The survival rate to hospital discharge is 58%, 46% and 30% in non-pregnant patients receiving ECMO for respiratory pathology, cardiac indications and ECPR, respectively.²⁶ Obstetric patients are a heterogenous group; and the nature of data collection and reporting makes it challenging to collect complete information. However, current literature suggests that this cohort of patients likely have more favourable outcomes than the general population. This should not be surprising given that obstetric patients are generally younger with fewer comorbidities than the general population. The survival rate for peripartum patients ranges across the literature but is reportedly 70–84%, 60–72% and 53–60% for respiratory, cardiac and ECPR, respectively.3, 4, 5^,14,27, 28, 29, 30

Peripartum patients who require ECMO may have neonates exposed to profound physiological derangement before cannulation or during the ECMO run. The current literature is limited in reporting neonatal outcomes. However, the available data for fetal survival for pregnancies associated with peripartum ECMO ranges from 64.7% to 67.9%.^3,4

Complications

The rates of complications associated with obstetric ECMO are also variably reported but trend similarly to the general patients receiving ECMO. The most common complications include bleeding (9–33%), VTE (2.8–5%), vascular complications in (3.9–9.5%), and neurological complications (5.3–14.7%).^{3,4,14,29,31,32} Byrne and colleagues studied a cohort of patients with COVID-19 ARDS requiring ECMO in pregnancy and found a much higher incidence of complications including VTE (39%), cardiac complications (which included myocardial infarction, cardiomyopathy, arrhythmia, shock, or cardiac arrest) (38%) and acute kidney injury (AKI) (27%), which is likely to relate to the underlying pathophysiology of the viral infection rather than ECMO.³¹ Although the rate of bleeding has been shown to be slightly higher in peripartum patients in some studies, the rate of mortality remains lower than in non-obstetric ECMO, suggesting that these complications can be managed to support these patients through survival.^4,27 Indeed, most ECMO patients do not require an intra-abdominal surgical procedure during the run and the need for delivery on or immediately before ECMO does increase the risk of haemorrhage. However, the risk of bleeding and surgical complications should not be considered a contraindication to ECMO given that the data support superior survival despite this risk.

Pregnancies associated with peripartum ECMO are more likely to end in preterm birth (43.1–52.3%) and accompanying morbidities including neonatal intensive care unit (NICU) admission (27.9%), intubation and neurologic complications are commonly encountered.^3,14,32 Although there are reports of premature labour, expulsion of the fetus, or both in pregnant patients on ECMO, the majority of preterm deliveries described in the literature are likely iatrogenic. A controlled premature delivery may be indicated for ongoing fetal distress despite optimisation of haemodynamics and oxygenation, to optimise maternal respiratory mechanics in the late third trimester, other maternal indications, or both as it may simplify care.

Emergency systems for ECMO in obstetric patients

Interhospital referrals and transport

The American College of Obstetricians and Gynecologists (ACOG) and the Society for Maternal-Fetal Medicine (SMFM) collaborated with various national organisations to create a system with defined levels of maternal care including antepartum, intrapartum and postpartum care.³³ The levels are dependent on healthcare facilities, availability and expertise of the obstetric provider, and consultant availability and expertise with Level I corresponding to basic care, Level II to specialty care, Level III to subspecialty care and Level IV to regional perinatal healthcare centres. All maternity facilities must be capable of stabilising and providing initial management for any obstetric patient while coordinating a transfer to a higher-level centre if needed. Patients who may require Level III or IV care to manage complications include those with: cardiac disease, placenta accrete spectrum, ARDS, liver failure, complex hematologic disease, pulmonary hypertension, and those requiring cardiac surgery or neurosurgery.³³ In the non-obstetric literature, patients with severe ARDS who are transferred to an ECMO specialty centre have improved survival outcomes, even if they do not ultimately require ECMO.³⁴ Expert management of the relatively rare critically ill parturient as early in the course of disease as possible may improve survival outcomes and reduce morbidity with earlier intervention and well-coordinated teams of consultants.

Extracorporeal cardiopulmonary resuscitation

Extracorporeal membrane oxygenation and ECPR have the potential to rescue patients after a cardiac arrest, during a cardiac arrest, or both and given the favourable outcomes in this population, integrating an ECMO response team into maternal cardiac arrest protocols, when possible, should be performed. When there is an in-hospital cardiac arrest, chest compressions should be rapidly initiated according to resuscitation guidelines with appropriate adjustments for pregnancy including manual uterine displacement and perimortem hysterotomy after 4 min of cardiac arrest.³⁵ The evidence suggests that younger patients, those who present with shockable rhythms, shorter down times, high quality CPR and percutaneous coronary intervention (PCI) are associated with favourable outcomes with ECPR.^36,37 Time to initiation of ECLS should be minimised and most clinicians agree that patients should be on full ECLS within 60 min of cardiac arrest, although survival is possible even in longer time periods of cardiac arrest.³⁶

It is challenging to provide expeditious cannulation in a cardiac arrest and implementing this technology during crises requires a substantial investment in resources, infrastructure, personnel and equipment.³⁸ Extracorporeal cardiopulmonary resuscitation crisis resource management includes staff awareness, automated system activation, facilities and equipment preparation, team organisation and training, and quality improvement and operations review.³⁸

Integrating an alert to an ECLS/ECPR team early in a maternal code can facilitate timely cannulation to ECMO and potentially improve outcomes in obstetric patients. Given the favourable survival and reversible nature of many peripartum indications for ECLS, this is an opportunity to improve survival in catastrophic events.

Conclusions

Extracorporeal membrane oxygenation teams should be contacted in advance for pregnant and peripartum patients that have known cardiovascular disease such as aortic stenosis, mitral stenosis, cardiomyopathy, pulmonary hypertension and a history of arrhythmias. Furthermore, patients with poorly controlled asthma, viral infections that require supplemental oxygen above usual amounts and advanced lung disease such as cystic fibrosis or interstitial lung disease should prompt early communication to the ECMO team for planning and awareness. Spontaneous arrest in pregnancy could be caused by amniotic fluid embolism, pulmonary embolism, or haemorrhage. With the exception of catastrophic intracranial haemorrhage, significant aortic dissection extending to femoral vessels, or both, ECMO can assist in rescuing many of these patients. Furthermore, even if the aetiology of cardiac arrest is found to be haemorrhagic after arrival of the ECMO team, they may be able to facilitate obtaining life-saving vascular access.

Given that it would be highly unusual for a pregnant patient to be ruled out as an ECMO candidate, we recommend immediate communication with an ECMO team in the case of a decompensating obstetric patient and suggest dissemination of contact information throughout maternal and obstetric wards to facilitate the process of activating ECMO.

Acknowledgements

The authors are grateful to Elise Ouellette and Neil Ray for their assistance with Figure 1.

Declaration of interests

JO received a one-time honorarium from La Jolla Pharmaceutical for a panel discussion on angiotensin II. EN declares that they have no conflict of interest.

MCQs

The associated MCQs (to support CME/CPD activity) will be accessible at www.bjaed.org/cme/home by subscribers to BJA Education.

Biographies

Emily Naoum MD is an attending anaesthesiologist and critical care physician at Massachusetts General Hospital. She is a clinical instructor at Harvard Medical School and serves as the Program Director of the Obstetric Anesthesia fellowship. She practices a mix of obstetric anaesthesia, surgical critical care, and general anaesthesia and has a research interest in maternal critical illness.

Jamel Ortoleva MD is a cardiothoracic anaesthesiologist, intensivist and ECMO team member at Boston Medical Center where he is an assistant professor in the Chobanian & Avedisian School of Medicine. He has active research interests in MCS, shock and intensive care.

Matrix codes: 1B04, 2B05, 3C00