5 Questions: Brendan Carvalho on CPR for pregnant patients
When a pregnant woman's heart stops, two lives are threatened. But until now, cardiopulmonary resuscitation guidelines have not adequately emphasized key differences in the CPR technique for pregnant patients nor given operational strategies to improve survival of both the expectant mom and her fetus.
Stanford anesthesiologists Brendan Carvalho, MD, Steven Lipman, MD, and Sheila Cohen, MD, led a team of experts assembled by the Society for Obstetric Anesthesia and Perinatology that has produced new expert recommendations, published in the May issue of Anesthesia & Analgesia, describing how to treat cardiac arrest in pregnant women. Carvalho, who is chief of obstetric anesthesia at Lucile Packard Children's Hospital Stanford and associate professor of anesthesiology, perioperative and pain medicine, talked with science writer Erin Digitale about the new recommendations and why they're needed.
Q: Why was the consensus statement needed, given that cardiac arrest in pregnancy is now rare?
Carvalho: We've cut maternal mortality significantly over the past century, but maternal death can still happen to any pregnant woman. All caregivers who treat pregnant women need to know how to handle cardiac arrest.
The American Heart Association publishes guidelines and runs courses on CPR, but special populations such as pregnant women are not adequately highlighted. The Society for Obstetric Anesthesia and Perinatology recognized this problem and commissioned a consensus statement by a team of experts. Stanford faculty led this effort and contributed a number of members to the expert team, including Kay Daniels, Julie Arafeh and Maurice Druzin. We came up with expert recommendations that clearly identify pregnancy CPR as a neglected aspect of resuscitation care. With better management of cardiac arrest in pregnancy, we can improve outcomes.
Q: Which women are at risk for cardiac arrest in pregnancy and why?
Carvalho: Cardiac arrest affects less than one in 20,000 pregnant women, occurring most frequently during labor and delivery. Women with high-risk pregnancies are at increased risk, such as those with cardiac disease. We're seeing this situation more frequently as sicker and older women are having babies. But some causes of cardiac arrest, such as hemorrhage, can affect any healthy pregnant woman. Amniotic fluid or pulmonary embolus, in which amniotic material or blood clots enter the bloodstream and triggers a cardiac collapse, can also affect any pregnant woman.
When cardiac arrest actually occurs, which is what our consensus statement addresses, you need to know how to optimize care. If you don't do good basic life support, women may come out alive but neurologically compromised. You can make a very big difference with basic techniques.
Q: How should resuscitation be modified for a pregnant patient?
Carvalho: When a patient's uterus becomes enlarged, it puts pressure on the big blood vessels that return blood to the heart. That affects the ability to perform effective CPR. In a nonpregnant patient, we can usually generate about 20 to 30 percent of normal cardiac output with CPR chest compressions, but in pregnancy, chest compressions generate only 10 to 15 percent of normal cardiac output. To minimize the problem, we recommend left uterine displacement: In addition to the person doing chest compressions, resuscitation teams should have a separate person who pushes the uterus to the patient's left side to relieve pressure of the uterus on the big veins. That's the first step. Historically, some experts suggested tilting the patient's entire body to the left, but it's extremely difficult to give effective compressions on a tilted patient.
Step two is that the team should deliver the baby as part of resuscitation for the mom. Historically, teams tried to save the mom for 45 minutes or an hour and then, if they couldn't revive her, they would try to get the baby out. But there have been case reports in which women spontaneously got their circulation back after the baby was taken out, because delivery relieves compression on mom's circulatory system. Delivery improves maternal survival as well as fetal neurological outcome and survival. So we're really emphasizing that resuscitation teams should aim to perform a C-section within five minutes of cardiac arrest. We talk about the logistics of doing this — for instance, a woman who has cardiac arrest in a labor and delivery room should have her C-section there. It doesn't make sense to move her to an operating room because the move delays delivery. It's also very difficult to give effective CPR while she's being moved.
Q: What aspects of resuscitation technique are the same for pregnant women as for other people?
Carvalho: Caregivers are often reluctant to administer medication to pregnant women because of potential harm to the baby. The consensus statement emphasized that caregivers can use the same drugs they typically give to a nonpregnant patient who has a cardiac arrest. The best thing you can do for baby is to provide the mom the best possible care and not withhold any drugs or procedures that would normally be used managing a critically ill person.
Q: Why are drills and simulations important for training obstetric caregivers to respond to a cardiac emergency?
Carvalho: Maternal cardiac arrest often happens in an environment that's used to healthy outcomes — most pregnant women and babies do well. Obstetric caregivers have much less experience dealing with cardiac arrest than people who work in the intensive care unit or emergency room.
The way that we've handled this at Lucile Packard Children's Hospital Stanford, and the approach we encourage other hospitals to adopt, is by running a lot of drills and simulations. With carefully studied simulations and drills, we've learned a lot of life lessons that have prepared us for the real scenario, which fortunately happens very rarely. One example that Dr. Lipman's in-house team drill uncovered: Our trays of C-section tools did not contain a scalpel, the one critical instrument needed for a cesarean. This was a huge shock to everyone. It turned out that before non-emergency cesareans, the obstetric technicians add a scalpel at the last minute because the handle of our scalpel is plastic and would melt in the autoclave. Now we keep a separate, sterile, packaged scalpel in a locked drawer in every labor room. Simulations also help the staff learn their roles, so that each person knows what to do in a real emergency.
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