Cardiac diseases represent around 10% of all maternal deaths.1 Maternal cardiac arrest, specifically, represents a highly challenging clinical scenario that is estimated to occur in around 1 in 30,000 pregnancies worldwide. Cardiac arrest is defined generally as the abrupt loss of heart function, which requires immediate therapeutic intervention in the form of resuscitation or other methods for successful outcomes.2
There are several proposed causes of maternal cardiac arrest, which may be a result of pregnancy or a pre-existing condition. Obstetric related causes include hemorrhage, preeclampsia, HELLP syndrome (hemolysis, elevated liver enzymes, and low platelets), amniotic fluid embolus, peripartum cardiomyopathy, and complications from anesthesia.1 In particular, iatrogenic complications of treating preeclampsia with magnesium sulfate can cause magnesium toxicity and fluid overload, both of which contribute directly to cardiac arrest. 1,3 Non-obstetric causes include pulmonary embolism, septic shock, cardiovascular disease, myocardial infarction, endocrine disorders, and collagen vascular disorder.1
In treating maternal cardiac arrest, physiological changes related to pregnancy should be taken into account when determining management methods. These changes are referred to as the “ABCs of maternal physiology.” The “A” represents airways, as pregnant patients are viewed as having a difficult airway which leads to increased chance of failed intubations. Furthermore, airway during pregnancy is smaller, and includes changes such as hyperemia, hypersecretion, and edema.4 The B, which represents breathing, is due to the increased risk of oxygen desaturation from increased oxygen consumption and reduced functional residual capacity.5 However, overventilation can also cause uterine vasoconstriction and fetal hypoxemia.6 The C represents circulation, which is of concern due to the possibility of aortocaval compression through the gravid uterus, which can compress the inferior vena cava.5 Thus, hemodynamic optimization requires effective aortocaval depression, which can be achieved through manual left uterine displacement and simultaneous chest compression.5
Given these physiological considerations, there are several recommendations for instability management and response. First, the patient should be placed into a full left lateral decubitus position for relief of aortocaval compression.7 In order to prevent hypoxemia, 100% oxygen should be administered through face mask.7 The gravid uterus should not obstruct intravenously administered therapies, which requires access above the diaphragm.7 Chest compressions are recommended for resuscitations, and the guidelines for pregnant patients remain the same as those for general adults.8 Utilization of defibrillator pads will determine the need for biphasic defibrillation.8 Pharmacological agents administered can include epinephrine, calcium (given magnesium sulfate toxicity), and amiodarone (for ventricular fibrillation).8 Anesthetic toxicity has been explored as a potential cause for maternal cardiac arrest – if this is the case, administration of the anesthetic should cease immediately.8
With multiple factors considered, the maternal code blue response team consists of obstetrician/maternal-fetal medicine specialists, anesthesiologists, cardiologists, neonatologists, intensivists, and cardiovascular surgeons, among others. An important decision made by this team can include perimortem caesarean section. Because brain injury occurs within 4 minutes after cardiac arrest, current protocol dictates that if resuscitation is not successfully achieved within those 4 minutes, perimortem caesarean section should be initiated with the goal of delivery 5 minutes after onset.8,9
Maternal cardiac arrest remains a significant source of maternal mortality. Successful resuscitation and recovery of both the mother and child requires understanding of the physiological and anatomical changes that accompany pregnancy, as well as a diverse physician team in order to maximize survival.
1. Whitty, J. E. Maternal Cardiac Arrest in Pregnancy: Clinical Obstetrics and Gynecology 45, 377–392 (2002).
2. Patil, K. D., Halperin, H. R. & Becker, L. B. Cardiac Arrest: Resuscitation and Reperfusion. Circulation Research 116, 2041–2049 (2015).
3. Swartjes, J. M., Schutte, M. F. & Bleker, O. P. Management of eclampsia: cardiopulmonary arrest resulting from magnesium sulfate overdose. European Journal of Obstetrics & Gynecology and Reproductive Biology 47, 73–75 (1992).
4. Hegewald, M. J. & Crapo, R. O. Respiratory Physiology in Pregnancy. Clinics in Chest Medicine 32, 1–13 (2011).
5. Jeejeebhoy, F. M. & Morrison, L. J. Maternal Cardiac Arrest: A Practical and Comprehensive Review. Emergency Medicine International 2013, 1–8 (2013).
6. Tomimatsu, T. et al. Maternal Hyperventilation During Labor Revisited: Its Effects on Fetal Oxygenation. Reproductive Sciences 19, 1169–1174 (2012).
7. Jeejeebhoy, F. M. et al. Cardiac Arrest in Pregnancy: A Scientific Statement From the American Heart Association. Circulation 132, 1747–1773 (2015).
8. Zelop, C. M., Einav, S., Mhyre, J. M. & Martin, S. Cardiac arrest during pregnancy: ongoing clinical conundrum. American Journal of Obstetrics and Gynecology 219, 52–61 (2018).
9. Beckett, V., Knight, M. & Sharpe, P. The CAPS Study: incidence, management and outcomes of cardiac arrest in pregnancy in the UK: a prospective, descriptive study. BJOG: An International Journal of Obstetrics & Gynaecology 124, 1374–1381 (2017).