Table 1 summarizes specific cardiopulmonary considerations for ECMO in pregnant patients. Multidisciplinary team planning is essential for this population and involves numerous medical and surgical specialties, as well as other specialist health professionals (eg, pregnancy heart team).[6,7]Table 2 lists common medications used during ECMO support, as well as their fetal effects. General principles for obstetric critical care are described elsewhere.[9–12]
The indications and contraindications for ECMO during pregnancy are similar to those for the general population (Table 3). The most common indication for venovenous (VV) ECMO in pregnant and postpartum patients is acute respiratory distress syndrome (ARDS), accounting for up to 49% of reported cases. Among these cases, severe viral pneumonia (ie, H1N1 influenza) is the dominant etiology, while other causes of ARDS, such as bacteremia, aspiration, trauma, or hypertensive disorders of pregnancy, together represent only a small minority of cases. Although pregnant patients are susceptible to severe coronavirus infections (eg, severe acute respiratory syndrome [SARS], Middle East respiratory syndrome [MERS], and coronavirus disease 2019 [COVID-19]), these infections are poorly represented in the reports of ECMO for obstetric patients.
Cardiovascular indications for venoarterial (VA) ECMO tend to be heterogeneous and may be more likely to present or require treatment in the postpartum period rather than antenatally.[1,14,15] These indications have typically included preexisting cardiomyopathy, peripartum cardiomyopathy, pulmonary embolism, amniotic fluid embolism, and cardiac arrest. While the majority of pregnant or postpartum patients on VA-ECMO support survive to discharge, those who require ECMO for pulmonary embolism or cardiac arrest may have superior survival compared to those with cardiomyopathy, which may be less reversible.[14,15]
Maternal inhospital survival for pregnant and peripartum patients requiring ECMO has greatly improved, from 46% 2 decades ago up to 75% presently.[1,15,16] In the Extracorporeal Life Support Organization (ELSO) registry, survival rates for obstetric patients now exceed those of the general adult population.[15,17] ECMO may be particularly beneficial for pregnant patients in the setting of acute cardiac arrest, improving survival to 88% compared to a 59% population-based cardiac arrest survival rate. Fetal survival is similarly favorable, around 70% to 75%.[1,16] Pregnant patients with ECMO initiation within 5 days of admission may have improved survival compared to delayed cannulation. Thus, we encourage early referral to a specialized center for consideration of ECMO.
Cannulation is similar as for nonpregnant patients (Figure 1). However, aortocaval compression by the gravid uterus may impede femoral guidewire advancement; therefore, it is helpful to have a cushion under the right hip to provide left uterine displacement during this process. After experience with a variety of cannula configurations during pregnancy, our current practice in VV-ECMO is to use a single-stage 25-Fr drainage cannula in the right femoral vein and a 23-Fr return cannula in the right internal jugular vein, which is well tolerated and ensures adequate flow rates. As in nonpregnant patients, femoral artery cannulation for VA-ECMO risks critical limb ischemia, so distal perfusion cannula placement during primary cannulation is often performed to prevent this complication.
Commonly used cannulation configurations for VV- and VA-ECMO. A, Internal jugular-femoral configuration for VV-ECMO. Blood is taken (outflow/drainage cannula) from the femoral vein and returned (inflow/return cannula) to the right internal jugular vein after passing through the oxygenator. B, Femoral-femoral configuration for VA ECMO. A cannula is placed in the femoral artery to provide retrograde blood flow to the heart. A drainage cannula is placed in the contralateral femoral vein. ECMO indicates extracorporeal membrane oxygenation; VA, venoarterial; VV, venovenous.
Anesth Analg. 2022;135(2):277-289. © 2022 International Anesthesia Research Society