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Cardiac arrest in pregnancy. SEMINARS IN PERINATOLOGY 42(2018)33–38. https://doi.org/10.1053/j.semperi.2017.11.007
MATERNAL PHYSIOLOGY
– The maternal heart rate increases by 20–30% or 15–20 beats per minute
– Cardiac output increases by 30–50% or 1.8 L per minute with the uterus receiving approximately 17% of maternal cardiac output in the third trimester.
– The diaphragm elevates by up to 4 cm in the third trimester causing decreased chest compliance
– Functional residual capacity decreases by up to 25% in the supine position at term.
– Pregnant patients experience mild respiratory alkalosis.
AORTOCAVAL COMPRESSION (ACC)
– Aortocaval compression (ACC) needs to be addressed during cardiac arrest management.
– The American Heart Association recommends manual left uterine displacement (LUD) throughout resuscitative efforts and during perimortem cesarean section until delivery of the infant.
– In the past, ACC was addressed by placing the patient in a tilt; however, this is no longer recommended.
– Numerous studies have shown that maternal tilt decreases efficacy of chest compressions, which hinders resuscitative efforts.
– Successful manual LUD can be performed from the patient’s right and left side.
– From the right side, the uterus is pushed upward and leftward to relieve pressure from the maternal vessels.
– Care should be ensured that the uterus is not inadvertently pushed down.
ETIOLOGY
– The most common cause of maternal mortality is venous thromboembolism followed by preeclampsia and eclampsia.
– In an analysis of cardiac arrest in pregnancy in the United States the most common causes of arrest were hemorrhage, heart failure, amniotic fluid embolism, and sepsis.
RESUSCITATION
– Chest compressions are performed in the same manner as for non-pregnant patients with a rate of 100–120 compressions per minute and a depth of at least 2 in with minimal interruptions.
– The most recent guidance state that hand placement for chest compressions should be in the center of the chest on the lower portion of the sternum in the same manner as for non-pregnant patients.
– Bag-mask ventilation with 100% oxygen with a rate of at least 15 L/min should be initiated immediately with a compression–ventilation ratio of 30:2.
– Early defibrillation should be provided when appropriate, and modifications in shock energy are not indicated. Studies have shown that transthoracic impedance is unchanged in pregnant patients. Providers should not delay or withhold defibrillation due to concerns for fetal safety. During defibrillation, a minimal amount of energy is transferred to the fetus, and it is safe to defibrillate a patient at any stage of pregnancy.
– Since airway management is more challenging, intubation should be attempted by the most experienced provider available with the use of a smaller endotracheal tube with a 6.0–7.0mm inner diameter to increase the likelihood of successful intubation.
MEDICATIONS
– Medical therapy for cardiac arrest in pregnancy is no different than for non-pregnant patients.
– Medications do not require dose alterations, and no medication should be withheld due to concerns for fetal teratogenicity.
– During active CPR, the AHA guidelines recommend against fetal assessment, and all fetal monitors should be removed from the patient. The goal of CPR is to restore circulation in the pregnant patient. Evaluating the fetal heart rate is not helpful at this time and can interfere with maternal resuscitative efforts.
PERIMORTEM CESAREAN DELIVERY (PMCD)
– PMCD should be initiated after 4 min of failed resuscitative efforts with the goal of delivery within 5 min of initiation of resuscitative efforts.
– As a caveat, if the mother has clearly non-survivable injuries, it is not necessary to wait to begin the PMCD. Transfer to the operating room is not recommended.
– With regards to technique for cesarean section, both vertical and Pfannenstiel incisions are acceptable and are at the discretion of the obstetrician. If the underlying arrest is secondary to trauma, a vertical incision is preferred given that it provides better visualization of the abdomen.
POST RESUSCITATION
– If restoration of spontaneous circulation (ROSC) has been achieved without undergoing a PMCD, the patient should immediately be placed in the full left lateral decubitus position.
– The 2015 AHA guidelines now state that pregnancy is not an absolute contraindication, and therapeutic hypothermia can be considered on an individual basis.
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