Hello everyone, my name is Brian Gasson and today I'll be talking to you about non-obstetric surgery during pregnancy. I have no financial relationships with any commercial interests related to the content of this activity and I will not discuss off-label use during this presentation. Our learner outcome is going to be to discuss anesthetic considerations for pregnant patients during the antepartum period. Approximately 1-2% of all pregnancies are complicated by requiring some type of surgical procedure in the United States and today that translates to about 75,000 of these surgeries get done annually here. They seem to be more or less distributed evenly across trimesters, probably heavier in the first followed by the second and then lastly only about a quarter of these or a little less are done in the third trimester. By far the common surgeries are generally of these categories, laparoscopic, gin surgery, composed of torsioned ovaries, ovarian cysts, appendectomies, cholecystectomies as far as laparoscopic procedures, cervical incompetence and McDonald's cerclage procedures are done commonly in pregnancy as well and then trauma. Trauma not only motor vehicle accident style trauma but orthopedic fractures. Now less commonly but nonetheless done are oncologic procedures for diagnoses that are made during the course of the pregnancy and rarely we see fetal surgery. When it comes to the timing of non-obstetric surgery during pregnancy, it is clearly indicated to postpone it until after pregnancy when possible. The only trouble is very few of these surgical procedures are elective. The vast majority of them just simply have to be done so we frequently don't have a choice with respect to that. All things considered we like to avoid the first and the third trimester, the second trimester being the best for surgery if you have the choice compared to the third trimester the risk of preterm labor is lower in the second trimester and compared to the first trimester organogenesis is largely complete by the time our patients are in the second trimester. But as I've indicated most surgeries involve acute illnesses or injuries and there's just simply not a choice. In order to really assess maternal risk and understand what's happening there we've got to really also understand some of the physiology that comes along with being pregnant and the risk that's associated with these procedures is not only reflected on the mom but there is also significant fetal risk in performing surgery. The fetal risk can be a problem of the disease process itself. It could involve teratogenicity of the anesthetic agents or as a result of treatment with the drugs needed to treat cancer for example and a lot of the fetal risk can also come from intraoperative changes in maternal status such as low blood pressure which can negatively affect utero placental perfusion and there is an ever-present risk of preterm labor in particular in the third trimester. Some of the respiratory effects associated with pregnancy are an increased oxygen consumption and a decrease in FRC. Difficult airway associated with pregnancy is due primarily to not only awakening but capillary engorgement of the airway which is just as much a factor early in pregnancy as in late pregnancy. There's a rapid induction in these patients due to decreased FRC and an increased cardiac output also factored into that is an increase in the alveolar ventilation and realize that pregnant women have a decrease in their MAC by up to 40%. Aorto-cable compression becomes a factor after 20 weeks gestation and if untreated that is if you do not use left uterine displacement can decrease cardiac output by up to 30%. We also realize as well when it comes to the cardiovascular system that all pregnant women are in a hypercoagulable state and any pregnant woman who undergoes surgery needs to have DVT prophylaxis steps. So we can consider teratogenicity from a kind of an overall or a general perspective. DVT prophylaxis generally occurs about 30 to 70 days following gestation where defects are often associated with structural defects within the organs. Central nervous system development then higher order central nervous system development occurs up to 126 days after conception which can result then in structural defects within the central nervous system. So the question of structural functional deficiencies is an interesting concept that has been discussed in the literature here in the last several years and it appears to be associated with exposure to drugs, exposure to surgery and exposed to teratogens in the third trimester. So when it comes to the specific teratogenicity of anesthetic drugs, for example, there are well-known effects of our anesthetic drugs on mammalian cells but to date there's no data that specifically links any anesthetic drug to any teratogenic change. Now having said that, studies are obviously hard to design and execute because they would require large numbers of patients exposed to the same drugs which we're really not going to do in our pregnant population. But I think it is important to restate that to date there is no indication that there is any anesthetic drug that has been specifically linked to teratogenic changes. Nitrous oxide may inhibit DNA synthesis but that was in an animal model, namely in a rat, and furthermore it was a result of a very long-term exposure. So the effect of nitrous oxide on humans and in particular fetal human beings is really inconclusive. However, there's few cases admittedly where we really have to use nitrous oxide so all things considered that might be a drug that we just stay away from. Ionizing radiation clearly carries with it a dose-related increase in malignancies and the congenital anomalies that follow it. However, radiation is often an important part of a proper diagnosis for a pregnant woman who requires surgery. So the recommendations currently are that we shouldn't avoid any diagnostic procedure that involves ionizing radiation just because a woman is pregnant that would otherwise put her life in danger. Thirdly, there are other known teratogens. I mean there are drugs that are not anesthetics, namely androgens, Coumadin, Dilantin, ACE inhibitors are prescribed for use during pregnancy, Accutane, Lithium Valproic Acid, Thalidomide for example, historically. I mean there are well-known teratogens but conspicuously absent from that list of well-known teratogens are any commonly used anesthetic drugs. So as I've indicated, clinical trials in humans are just not going to happen for all the obvious reasons. We do have, however, limited data. We have limited data from, for example, non-obstetric surgery in pregnancy. And when we look at outcome studies, we have surveys of OR staff or surveys of staff from dental offices, for example, where they are exposed to nitrous oxide. And then there are animal studies. The problem with animal studies being that it's difficult to make conclusions across species that is from an animal to a human being when it comes to teratogenic effects. And so back to nitrous oxide, I mean, there were animal studies that exposed animals, rats to nitrous for the equivalent of 24 hours that were in and of themselves somewhat inconclusive in their results. And it may have even been, the negative findings may have even been from the sympathetic stimulation caused by the long-term nitrous exposure that is of 24 hours or so. A lot of the extrapolation that we've seen with respect to nitrous oxide are reproductive outcome studies from women with occupational exposure, namely dental offices where scavenging systems are just not used. And so nitrous remains a fairly controversial drug that with that controversy and knowing that it's probably, you don't have to use nitrous, would be a drug that we could avoid using. The FDA categorizes drugs according to risk in pregnancy as A, B, C, D, and X. A drugs are okay for pregnancy use because there are controlled studies that demonstrate no risk. And when we look at our commonly used anesthetic agents, there are no drugs that have been researched in a controlled environment and demonstrated no risk. B drugs are drugs where there is no evidence of risk in humans, just based on experience. And C drugs are drugs where you cannot rule out risks. And most of our IV induction agents are gonna be found, if you look in their package inserts, they're gonna be found as either pregnancy class B or C. Our neuromuscular blocking drugs are pregnancy class C. And opiates will also be, along with local anesthetics, class B or C drugs as well. When we look at our volatile anesthetic agents, and in particular with animal studies, there is no evidence of teratogenesis under normal physiologic conditions with respect to our volatile anesthetic agents. In human beings, there is also no sign of no increase in congenital anomalies in pregnant women undergoing general anesthesia. And there has been no increase in congenital anomalies in OR personnel who are, for example, chronically exposed to small amounts of volatile anesthetics. Overall, when the effect of surgery is examined on a fetus, there is an increased incidence of spontaneous abortion, spontaneous miscarriage, intrauterine growth retardation, and overall perinatal mortality. It appears to be related to the surgical site and the procedure, as well as the maternal condition, the type of anesthetic that's utilized, and individual anesthetic agents appear at this point to have no effect whatsoever. And so, as far as general considerations when it comes to anesthetizing a pregnant person for a non-obstetrical procedure, it all comes down to timing and your wish and desire is, of course, to avoid all surgery until the pregnancy is ended. However, if you can't do that, there's mechanical things and then timing. So the mechanical things you want to pay attention to are always maintain left uterine displacement under about 20 weeks gestation. Maintaining uteroplacental perfusion is going to be critical for fetal well-being, and left uterine displacement is a significant part of that. Use the lowest possible peritoneal pressure during laparoscopic surgery, all right, well below the standard 16 to 20 centimeters of water. Use only what's necessary to perform the procedure surgically. Definitely avoid over ventilation. Over ventilation drives down the pH, which constricts uteroplacental perfusion. And you might consider, and we'll talk a little bit about this going forward, you might consider fetal heart rate monitoring after the child is determined to be viable, which is generally accepted to be around 24 weeks. Always use good DVT thromboprophylaxis to include pneumatic stockings. And as we've talked about earlier, avoid the first trimester and avoid a third trimester when possible to avoid impacting organogenesis and preterm labor. So strategies to maintain uteroplacental perfusion include avoiding maternal hypercapnia. Fetal acidosis and myocardial depression can result from that. We want to always maintain maternal PO2. Hyperoxia has not been found to be detrimental to the fetus during surgery, prenatal surgery. And transient decreases, just brief periods of decrease in PO2 is normally well tolerated, but clearly, clearly prolonged and profound decreases in maternal PO2 is a problem and can often be fatal for the baby. We want to avoid maternal hyperventilation. The respiratory alkalosis, as we've said, is a uterine artery vasoconstrictor and ultimately decreases uteroplacental perfusion and shifts the maternal oxyhemoglobin curve to the left. Never forget that MAC in pregnancy is decreased and it's decreased substantially by around 40% in term. And so what this tells us is our patients will be carried deeper, deeper at a conventional anesthetic dose. When considering to monitor the fetus intraoperatively, there's a few questions that you should really answer in conjunction with working together with your team, team being perhaps maternal fetal medicine, the obstetrician, anesthesia, and surgery. Namely, is fetal monitoring really going to be compatible with a surgical site? Often where they're working in the abdomen is not really going to be conducive to keeping a monitor on this person. Have you consulted with an obstetrician or maternal fetal medicine? Are they in agreement that this fetus is viable and as such, we should be monitored carefully during surgery? And if that's the case, you want to make sure that you have a surgeon available with privileges to deliver that child if in fact there is a decrease in the fetal heart tones. Is there a plan? You need to have a plan in place that everyone has agreed upon, including the mom and the parents of this child. And are they consented to that plan? Is this person consented to a cesarean section while asleep if this child's condition deteriorates during the course of the surgery? And furthermore, these fetal heart tones should be interpreted by a trained person, namely a labor delivery nurse to adequately make a determination of whether the child's doing well or not. Okay, so a couple more thoughts on fetal monitoring intraoperatively. Know that as we put a pregnant mom to sleep, decreased variability is consistent with a sleeping baby. And so really what we're looking for as far as deterioration in fetal status would be late decelerations. Induction agents, opiates, volatile agents all decrease variability, and decreased variability should happen when a mom is adequately anesthetized. Sympathomimetics as well can result in fetal tachycardia when absorbed across the placental barrier. So preterm labor, preterm labor remains one of the more common and vexing concerns of particular third trimester surgery and occurs in up to 22% of third trimester surgeries. Volatile anesthetics have a theoretical benefit, although there's no science to really back that up. Volatile anesthetics being smooth muscle relaxers. Prophylactic administration of tocolytic drugs such as magnesium, tributylene, or endomethicin haven't been shown to be of benefit at all, but they are used to treat preterm labor once it occurs. And so third trimester patients undergoing laparoscopic surgery, for example, really probably ought to have their intraop, their contractions monitored intraop. And you ought to have a plan in conjunction with an obstetrician about what you're going to administer and in what dose to treat preterm labor if it occurs. So then to summarize the effects of non-obstetric surgery and pregnancy on the fetus, there is a clear increased incidence of preterm labor and spontaneous abortion, fetal growth restrictions, and overall perinatal mortality. It's often not attributed to anesthetic drugs or anesthetic techniques, but is attributed to the procedure, the surgical site, and the maternal condition. There is no evidence, again, none that anesthesia increases the chance of congenital abnormalities. So when creating an anesthetic plan for a pregnant patient for a non-obstetric surgery, you ought to think about carefully examining or carefully evaluating any complications of the pregnancy to date. Clearly, a careful airway assessment is indicated. An obstetrical consult is also indicated at which time you can determine whether you'll be monitoring for fetal heart tones. And aspiration prophylaxis as well as prophylaxis for PE, DVT prevention is a critical part of the care of these people as well. So anesthetic considerations for both regional and general anesthesia include the following. When it comes to anorexial anesthesia, a preload to minimize hypotension is important and should be used as you would in any pregnant person. Left uterine displacement when gestation is over 20 weeks. And there is no problem with supplemental oxygen in these patients as well. Carefully avoid hypotension and when it occurs, treat it and treat it well. And be careful with your sedation. You really want to maintain these patients airways. There is a question about benzodiazepines. And they have been shown in extended exposure to human beings to result in cleft palates, cleft lips. And so that being the case, at any point in pregnancy, I really think long and hard about administering a benzodiazepine. When it comes to general anesthesia, again, left uterine displacement is going to be critical for our patients who are greater than 20 weeks gestation. Due to the decrease in their FRC and increase in oxygen consumption, careful and effective pre-oxygenation is critical. Our patients require rapid sequence inductions and really need to be treated. And realize that they are predisposed to difficult airways. So know your algorithm and consider strongly the use of video laryngoscopy from the get-go. So during the maintenance phase of the anesthetic in a patient with a general anesthetic, strive to maintain normal carvia. Keep your oxygen at 50% or greater. Aggressively treat any hypotension and know that volatile agents, because they decrease uterine tone, are a good option for you. Opiates as well are not to be avoided. They are acceptable if delivery is really not anticipated. And with respect, again, to nitrous oxide, absent maternal benefit, and there rarely is, it should generally be avoided. If used, you want to keep the concentration less than 50%. And surgeries that are long, you probably want to avoid its use as well. So in the recovery phase, in PACU, you're going to want to want to monitor these patients for onset of preterm labor. And again, if viable, fetal heart tones. And they may probably spend 24 hours in labor and delivery following their PACU stay to monitor again for preterm labor and to monitor the fetal heart tones. Regional anesthesia is always an option in these patients and is recommended for all the right reasons. It can provide for effective post-op analgesia. And don't forget venous thromboembolism prophylaxis. Thanks for your attention.

non-obstetric surgery

pregnancy

anesthesia

second trimester

fetal monitoring

maternal safety