Pregnancy and Cardiac Arrest (ALS 436)
EREV #1 Jill Mhyre
EREV #2 Carolyn Zelop
There are no RCTs evaluating the effect of specialized obstetric resuscitation versus standard
care in postarrest pregnant women.
Uterine displacement
No direct evidence is available to demonstrate how non-invasive maneuvers to relieve
aortocaval compression might impact outcomes in the pregnant woman receiving chest
compressions. The effects of the full lateral position, lumbar-pelvic tilt, full table tilt, and
manual displacement of the uterus have been evaluated in simulation mannequins, third
trimester pregnant women before and during labor, and in healthy term pregnant women
undergoing the induction of spinal anesthesia for cesarean delivery.(1-16) The full lateral
decubitus position is the most effective position to relieve aortocaval compression,(3, 16) but
less extreme degrees of pelvic tilt may improve maternal blood pressure, cardiac output, and
stroke volume, (1-3) and fetal parameters of oxygenation and fetal heart rate.(7-9) Leftward tilt
of the entire maternal patient (e.g., on a full-body back board or operating room table)
increases the work required to administer high quality chest compressions,(17, 18) displaces
the maternal heart laterally,(19) and may result in less forceful chest compressions(11) when
compared with positions that maintain the thorax in a supine position (e.g., leftward pelvic tilt
or manual displacement of the uterus). Manual left uterine displacement with the patient in the
supine position appears to be at least as effective as 15◦ left lateral tilt to relieve aortocaval
compression, based on two RCTs of pregnant women undergoing spinal anesthesia for cesarean
delivery.(14, 15) The combination of left lumbar-pelvic tilt and manual displacement has not
been studied.
The mechanism of how uterine displacement maneuvers might improve maternal
hemodynamics is not elucidated. Residual aortic compression has been documented in nonlaboring term pregnant women positioned with 15◦ left lateral tilt,(2) and in laboring term
pregnant women positioned with up to 30◦ left lateral tilt.(20) No study has evaluated for
residual aortic compression caused by manual left uterine displacement. Likewise, increased
compression of the inferior vena cava has been documented in a minority of non-laboring term
pregnant women positioned with 15◦ left lateral tilt when compared with the supine
position.(6) Leftward pelvic tilt and manual displacement of the uterus may have variable
effects in different women. In cardiac arrest, these maneuvers may exert their greatest initial
maternal benefit by compressing the aorta, thereby increasing maternal diastolic blood
pressure, coronary perfusion, and cerebral perfusion pressures. However, any aortic
compression increases maternal cardiac workload, and decreases blood flow to the uterus,
placenta and fetus. Thus peri-mortem delivery, the ultimate decompression of the uterus,
becomes the next step in the resuscitation algorithm.
Perimortem Delivery
Several observational designs have reported data on the effect of perimortem delivery on
maternal ROSC, maternal survival to discharge, and neonatal survival among pregnant women.
The overall quality of these studies is very low. Most reports of perimortem delivery focus on
perimortem cesarean section. Perimortem vaginal delivery may be possible if cardiac arrest
transpires at complete cervical dilation and advanced fetal station. As in non-arrested women,
the preferred route of delivery depends on obstetric considerations, and all studies that
evaluated the impact of perimortem delivery on maternal and neonatal survival were
considered together, regardless of the route of delivery.
One retrospective cohort study of 55 maternal cardiac arrests evaluated the incidence of perimortem cesarean delivery after the introduction of a training course and compared it with a
historical rate generated from an earlier time interval encompassed by the overall study
period.(21) Twelve cases of perimortem cesarean delivery between 1998 and 2008 were
ascertained by national survey of obstetricians and resuscitation trainers. A control group of
pregnant women who experienced cardiac arrest without perimortem delivery was drawn from
the Dutch Maternal Mortality Confidential Enquiries (n=35) and from a national study of severe
morbidity for the years 2006-2008 (n=8). Due to the differential methods of ascertainment, the
data is not appropriate for comparison.
Several systematic reviews of case reports of maternal cardiopulmonary resuscitation have
been published.(22, 23) In the most recent review, outcomes were more favorable among the
reported cases that did not undergo perimortem delivery; publication bias may explain these
results. Multivariate analysis of data from 95 case reports demonstrates an association
between PMD completed within 10 minutes of cardiac arrest and maternal survival.(23) The
time interval between maternal cardiac arrest and delivery was shorter for both maternal
survivors compared with non-survivors (107.2 vs  minutes) and for neonatal
survivors compared with non-survivors (14 vs.  minutes).(23) More rapid delivery
(<10 minutes) may improve outcomes, but the available data does not allow calculation of a
specific point estimate for optimal time interval from maternal cardiac arrest to delivery.
A subsequent single-institution case series of 5 cases of maternal CPR describes an experience
that is consistent with these findings.(24)
Treatment Recommendation
There is insufficient evidence to support or refute the use of specific resuscitation techniques
for maternal cardiac arrest. However, available evidence suggests that aortocaval
decompression and perimortem delivery each may improve maternal and neonatal outcomes in
pregnant women with cardiac arrest in the second half of pregnancy. No specific interventions
beyond standard resuscitation have been demonstrated to improve outcomes for
cardiopulmonary resuscitation during the first half of pregnancy.
Knowledge Gaps
Research in the area of maternal resuscitation is lacking because cardiac arrest in pregnancy is
rare.(25) Most evidence is extrapolated from non-pregnant people, mannequin studies, or case
reports. The heterogeneous nature of the etiologies of maternal cardiac arrest, as well as
variations in demographics, gestational age and body mass index of the cases all further
hamper interpretation of available data. Systematic data collection in pregnant women who
have experienced cardiac arrest will require the development of a national or international
registry with or without coordinated prospective population-level surveillance. A particular
emphasis on cardiovascular etiologies of arrest is warranted given increasing numbers of
women with congenital heart conditions having children,(26) the increasing prevalence of
cardiomyopathy among pregnant and postpartum women,(26, 27) and the preponderance of
cardiovascular disease evident in maternal mortality surveillance reports.(28, 29)
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