What the Anesthesiologist Should Know before the Operative Procedure
Fetal surgery encompasses a broad range of possibilities, ranging from minimally-invasive procedures using 17-gauge needles, to complex cases that require two anesthesia teams, two operating rooms, and a team of neonatologists. These cases are truly multidisciplinary and communication between all teams is essential. An understanding of fetal and uteroplacental physiology is key, as well as familiarity with fetal disease processes. While the fetal pathology is the reason for the surgery, the safety of the mother must never be forgotten. The surgical plan should be clear, and contingency plans should be made should fetal distress occur intraoperatively.
Three general situations where surgery is indicated:
Intervention for fetus or fetuses at risk for death in utero (twin-twin transfusion syndrome, or tumors causing hydrops fetalis).
Intervention to prevent or palliate morbidity after birth (myelomeningocele, hypoplastic left heart).
Intervention to allow fetus to make transition to extrauterine life (airway obstruction, or tumor impeding postnatal ventilation or cardiac function) also known as ex utero intrapartum therapy (EXIT procedure).
Minimally-invasive fetal surgery
These cases are typically performed to treat twin-twin transfusion syndrome or twin reversed arterial perfusion sequence. Fetal pleural effusions or lung cysts may necessitate one time needle aspiration or chronic drainage with a thoracoamniotic shunt. Lower urinary tract obstruction may also necessitate bladder decompression, which may be one time, serial, or chronic. Fetuses with selected congenital heart defects may be candidates for in utero cardiac catheterization. Surgical instruments (needles, lasers, catheters, etc.) are inserted percutaneously into the amniotic space and guided to the fetal structures of interest with ultrasound or endoscopic camera.
Open mid-gestation surgery
This is typically for cases of fetal myelomeningocele. The purpose is to protect the spinal cord from the amniotic fluid as it develops in utero. Other situations where open mid-gestation surgery may be indicated include resection of a solid lung tumor causing hydrops fetalis in a fetus with immature lungs (e.g., 23 weeks’ gestation). These cases involve maternal laparotomy, hysterotomy, fetal exposure, and surgery. At the end of the case, the fetus is replaced into the uterus to continue developing.
Ex utero intrapartum therapy
Ex utero intrapartum therapy (EXIT) procedures are performed near term, usually in cases of fetal airway obstruction, and occasionally for pulmonary pathology. While airway obstruction will likely not compromise the fetus in utero, the airway must be secured before the umbilical cord is clamped and the newborn takes its first breath. Pulmonary pathology may compromise the ability of the neonatal team to resuscitate the newborn (significant mediastinal shift from tumor mass effect), and an EXIT procedure may be indicated in these cases. At the end of the procedure the newborn is delivered to a neonatal team for further resuscitation. A second operating room and anesthesia team should be prepared to care for a newborn in extremis if the EXIT procedure is unsuccessful.
1. What is the urgency of the surgery?
What is the risk of delay in order to obtain additional preoperative information?
The urgency of each case depends on the specifics of the fetal and maternal situation. In some respects, all fetal surgery is elective, as the health and safety of the mother is most important. Emergent fetal surgery may, however, be indicated if the mother is beginning to develop maternal mirror syndrome. The appropriate treatment for mirror syndrome is treatment of the fetal pathology or delivery of the fetus. Surgery should proceed as soon as feasible to help both the mother and the fetus.
If the mother is healthy, willing and able to proceed, then emergencies may arise with respect to the fetus. The most emergent fetal surgery is an EXIT procedure in a mother whose amniotic membranes have ruptured, or who is starting to labor. If the fetus is not delivered via the EXIT procedure, it may die after birth from airway obstruction.
Urgent cases may evolve in the course of prenatal evaluation and care. New or worsening hydrops fetalis may be reason to perform surgery more urgently, depending on the degree of worsening of the hydrops.
The only truly elective case is repair of a fetal myelomeningocele. These cases are done around 23-26 weeks’ gestation.
In addition to the medical and surgical considerations that come with the urgent and elective fetal cases, timely, efficient and clear communication and contingency planning are crucial in cases of emergent fetal surgery. The necessary team members may include pediatric anesthesiologists, obstetric anesthesiologists, obstetricians, pediatric surgeons, otolaryngologists, neonatologists, operating room nursing and staff, neonatal nursing and staff, and possibly extra corporeal membrane oxygenation (ECMO) specialists and cardiologists. Medications and blood must be quickly prepared, as well as organization of the teams and operating rooms. The rarity of these cases means that the number of medical professionals familiar with the fetal surgical protocols is often only a small subset of the readily available staff. If the emergency occurs in off-hours, clear algorithms should be developed to help those unfamiliar with the protocols or to activate team members that are familiar with the protocols.
In addition to the considerations that come with elective cases, urgent surgery usually means that the fetus or the mother is getting sicker. A sicker fetus is more likely to decompensate, and as such, extra doses of emergency medicines should be prepared. Mothers undergoing open mid-gestation fetal surgery are at risk for developing pulmonary edema, and maternal mirror syndrome may also cause maternal pulmonary edema. Postoperative disposition may include the possibility of intensive care.
These cases are unique in that two patients are receiving anesthetic care. These patients, a pregnant woman and a sick fetus, both present higher anesthetic risk than the usual patient. The anesthetic team should be familiar with the anesthetic considerations of both sets of patients.
2. Preoperative evaluation
Fetal surgery involves a mother subjecting herself to an invasive procedure to save the life or improve the quality of life of her unborn fetus. The risk to the mother must be balanced with the potential benefits to the fetus. The health and safety of the mother are most important, and as such the mothers who are candidates for fetal intervention should be a highly selected population without major comorbidity.
The physiologic changes of pregnancy may cause some symptoms that merit further questioning.
Severity of reflux symptoms may impact the ability to perform sedation or monitored anesthesia care.
Symptoms of supine hypotension call for meticulous attention to blood pressure monitoring, uterine displacement, and availability of vasopressors.
Additionally neurologic or musculoskeletal conditions may impact the choice or ability to provide neuraxial anesthesia.
Medically unstable conditions warranting further evaluation include chest pain, shortness of breath, bleeding, uterine contractions (labor), fever, hypertension, seizures, new onset edema.
Delaying or cancelling surgery is indicated if the patient has any unstable conditions. Exceptions to this may include patients with preeclampsia or mirror syndrome. Do not forget the option of delivering the fetus and attempting resuscitating after delivery. This is not often an easy option, as the family is often very attached to the idea of “doing everything possible” for their child, but fetal surgery is a major undertaking, and if the mother is unstable, it will present a host of problems for the anesthetic management of these cases. Early and mid gestation fetal surgery should not be performed unless the uterus is “quiet,” as uterine manipulation will increase the likelihood of preterm labor.
3. What are the implications of co-existing disease on perioperative care?
b. Cardiovascular system
Patients with significant preexisting cardiac disease should be carefully screened, and the risks of proceeding with fetal surgery should be carefully balanced with the potential benefit to the fetus.
Acute/unstable conditions: Distinguishing between symptoms of pregnancy and symptoms of cardiac disease is important and may be difficult. While the likelihood of myocardial ischemia, unstable angina, or significant arrhythmia is low in this population, these possibilities should not be ignored, especially if symptoms have developed acutely. If history and physical do not clarify the patient’s symptoms, 12-lead EEG, echocardiography, and consultation with a cardiologist may be in order.
Baseline coronary artery disease or cardiac dysfunction – goals of management
Open fetal surgery should probably be avoided in patients with known coronary artery disease or cardiac dysfunction. The physiologic requirements of the anesthetic and surgery, which will be discussed later, place the patient at too great a risk for cardiac morbidity. The health of the mother remains the priority. If the mother is getting sicker due to mirror syndrome, the fetus (if viable) should be delivered and resuscitated to the best ability of the neonatal team. Patients with mild, stable coronary artery disease may be candidates for minimally-invasive fetal surgery, but all the teams involved must weigh the risks and benefits of fetal surgery. Minimally-invasive cases are often able to be done with monitored anesthesia care and infiltration of local anesthetic.
Valvular disease should be assessed as it is in other cases, with history focusing on symptoms of valvular dysfunction. Recent echocardiography should be reviewed.
Arrhythmia should be assessed with history, 12-lead electrocardiogram (ECG)/Holter, and assessment by a cardiologist. Deep inhalational anesthesia should not be administered to patients with a history of Wolff-Parkinson-White syndrome, as blockade of the AV node may predispose patients to arrhythmias.
Chronic hypertension must be distinguished from preeclampsia or maternal mirror syndrome. Proteinuria is suggestive of preeclampsia.
Perioperative risk management strategies
Just as in any patient with coronary artery disease, the goals should be to maximize oxygen delivery by reducing cardiac oxygen demand and increasing supply. If patients with stable arrhythmias are deemed candidates for surgery, they should be continued on their usual medications and emergency medications and equipment should be prepared to deal with these arrhythmias should they occur. Patients with anything more than mild valve disease are not good candidates for fetal surgery. Chronic hypertension should be managed as in any other pregnant patient, and blood pressure should be kept close to baseline for both maternal and fetal health. Preeclampsia should be treated as in other cases by delivery of the fetus.
Significant pulmonary disease may make a patient ineligible for fetal interventions. As with cardiac disease, physiologic changes of pregnancy may cloud the picture when trying to determine if dyspnea is primarily pulmonary in origin or if it is secondary to the pregnancy.
COPD/reactive airway disease
Most patients presenting for fetal surgery do not have primary pulmonary disease significant enough to change anesthetic management for fetal surgical cases. Patients requiring oxygen, or with very low exercise tolerance should not be candidates for surgery. The ability of the patient to lay supine with left uterine displacement is crucial for minimally-invasive cases, as these cases are often done under monitored anesthesia care. A history of a productive cough at baseline may make minimally-invasive procedures more challenging for the surgeons. The patient must be able to hold very still as the surgeons are performing critical procedures with needles, catheters, and lasers in the uterus. A history of severe, poorly controlled asthma or bronchospasm makes the patient a poor candidate for open fetal surgery, which is typically performed under general endotracheal anesthesia.
Perioperative risk management strategies
Maintenance of chronic pulmonary medications is reasonable. Pretreatment with bronchodilators may be helpful. Deep extubation is not a good option in pregnancy.
Significant preexisting renal or gastrointestinal disease is rare in this patient population. The most common gastrointestinal problem that arises is onset or worsening of gastroesophageal reflux. The severity of symptoms will not change management of open fetal surgery, as these cases are commonly done with general endotracheal anesthesia after a rapid sequence induction, but minimally-invasive cases are most often done under monitored anesthesia care.
If the patient has very severe reflux symptoms, the anesthesiologist could consider two options – very light or no sedation with local anesthesia, or general endotracheal anesthesia after rapid sequence induction. If local anesthetic infiltration with no or minimal sedation is chosen, the procedure may be technically more difficult for the surgeon, as they depend on placental transfer of medicines to decrease mobility and improve operating conditions. Fetal intramuscular injection may also help improve operation conditions, but this is rarely done. Aspiration prophylaxis should be considered for all patients for all cases of fetal surgery.
Neurologic issues in this population may include epilepsy. Cerebrovascular disease is rare, but symptoms of stroke or transient ischaemic attack (TIA) should be worked up fully.
Acute or evolving neurologic symptoms would be grounds for delay or cancellation of fetal surgery. An acute seizure due to preeclampsia should result in delivery of the fetus.
Chronic neurologic disease (epilepsy, multiple sclerosis, etc.), as long as it has been deemed stable, should not alter the anesthetic plan dramatically. Antiepileptic medications will likely have an impact on the metabolism of anesthetic medications.
Diabetes in gestation falls into several subtypes. Gestational diabetes is not likely to result in significant end organ damage, and unless insulin is required for management of blood sugars, will not change management significantly. Some may require more aggressive management of blood sugar. If insulin is required, or the patient was an insulin-dependent diabetic, blood sugar should be tested intraoperatively, and either sliding scale insulin or an insulin infusion may be started.
Patients with unstable thyroid disease should not be candidates for fetal surgery. The impact of a goiter on the airway should be assessed. Thyroid function tests can be reviewed, as well as any symptoms of hypo- or hyperthyroidism. Stable hypothyroidism should only require continuation of the current medications.
g. Additional systems/conditions which may be of concern in a patient undergoing this procedure and are relevant for the anesthetic plan (e.g., musculoskeletal in orthopedic procedures, hematologic in a cancer patient)
Back pain, lumbar disc disease, scoliosis, and prior back surgery may impact the decision to perform neuraxial anesthetic techniques in this population. The symptom assessment, patient counseling, and decision making should be the same as in any other pregnant patient potentially undergoing a neuraxial block.
Coagulopathic patients should not be candidates for fetal surgery.
Hypercoagulable states seem to be more frequent in the population of women presenting for fetal surgery. Attention should be paid to history of prior venous thrombosis or pulmonary embolism. Previous and current anticoagulation regimens should be detailed, and an appropriate plan for discontinuing anticoagulation for the procedure and restarting the anticoagulation should be made in conjunction with the surgical team and a hematologist. Sequential compression devices should be used to decrease risk of deep venous thrombosis.
4. What are the patient's medications and how should they be managed in the perioperative period?
Most patients are only on prenatal vitamins, which do not need to be continued in the perioperative period.
h. Are there medications commonly seen in patients undergoing this procedure and for which should there be greater concern?
Most patients presenting for fetal surgery are healthy and are not on any chronic medications. Prenatal vitamins do not need to be continued on the immediate perioperative period. Medications for treatment of chronic conditions should probably be continued, with the exception of anticoagulation or antiplatelet drugs. A conversation should be held with the surgical team and the person prescribing the anticoagulation regarding continuation of these medications in the perioperative period.
i. What should be recommended with regard to continuation of medications taken chronically?
Continue cardiac, pulmonary, renal, neurologic, and psychiatric medications. Continue thyroid medications; discuss insulin and oral hypoglycemic management with the team.
Antiplatelet medication: If a neuraxial technique is considered, follow the most current American Society of Regional Anesthesia (ASRA) guidelines. Briefly, non-steroidal anti-inflammatory drugs (NSAIDs) alone do not seem to pose increase risk of spinal hematoma. Avoid neuraxial techniques if that patients are receiving NSAIDS concurrently with other oral anticoagulants, unfractionated, or low molecular weight heparin. Two weeks should pass between discontinuation of ticlopidine, and one week should pass between discontinuation of clopidogrel and the initiation of a neuraxial block.
j. How to modify care for patients with known allergies:
Most commonly encountered allergies are easily managed with a readily available alternative. This includes medications, tapes, and prep solutions. Blood product allergies or reactions may be attenuated by pretreatment with diphenhydramine, acetaminophen, and steroids.
k. Latex allergy – If the patient has a sensitivity to latex (e.g., rash from gloves, underwear, etc.) versus anaphylactic reaction, prepare the operating room with latex-free products.
l. Does the patient have any antibiotic allergies? [Common antibiotic allergies and alternative antibiotics]
Clindamycin is our commonly used alternative to cefazolin.
m. Does the patient have a history of allergy to anesthesia?
A history of malignant hyperthermia (MH) must not only be sought in the mother, but also in the father, as the fetus may be at risk for MH if either the mother or father is MH susceptible.
Documented: avoid all trigger agents such as succinylcholine and inhalational agents.
Proposed general anesthetic plan:
Volatile anesthetic is a key component of the anesthetic for open fetal surgery. It is used at high concentrations, often 2 times minimum alveolar concentration to ensure uterine relaxation which is crucial in these cases and also to provide some degree of fetal anesthesia. If volatile anesthetic cannot be used, nitroglycerin infusions would be the next line drug to provide uterine relaxation, while fetal intramuscular injections could be used to provide fetal anesthesia.
The anesthesia machine should be prepared according to the established guidelines for the that particular machine.
Rocuronium 1.2 mg/kg would be a reasonable substitute for succinylcholine in a rapid sequence induction.
Ensure MH cart is available.
Family history or risk factors for MH
For minimally-invasive cases, it is quite easy to treat the patient as if she were documented to be MH susceptible. In cases of open fetal surgery, high-dose volatile anesthetic is a key component of the typical anesthetic management. If time allows it may be worthwhile to closely examine the family history and perform testing for MH susceptibility.
Local anesthetics/muscle relaxants
Allergy to the more commonly used amide local anesthetics is rare, but if the patient has a documented history of allergy, is it reasonable to avoid these medications. Allergy to neuromuscular blocking agents may be reason to consult an allergist for further evaluation or provocative testing if the practitioner requires guidance in selection of alternatives.
5. What laboratory tests should be obtained and has everything been reviewed?
For minimally-invasive procedures, unless otherwise indicated by the patient’s history, a type and screen should be the only lab test needed. For open fetal surgery, blood products should be available for both the mother and the fetus. Since the fetal blood type can not be easily determined, Type O negative blood should be used, but the O negative blood should still be cross matched against the mother’s blood sample as her antibodies to blood antigens cross the placenta into the fetal circulation.
Expect the “dilutional anemia” of pregnancy. It is good to have a baseline, as bleeding, although rare, can be rapid and catastrophic in open fetal surgical cases.
Should be in normal ranges.
Should be in normal ranges. Fibrinogen increases in pregnancy.
Not for the mother unless otherwise indicated, but the fetus will often have an extensive radiologic workup, and this should be reviewed. This will often include detailed fetal ultrasound examination, fetal echocardiography, and a maternal/fetal MRI.
Can be ordered and reviewed as the specific conditions of the mother or fetus warrant.
Intraoperative Management: What are the options for anesthetic management and how to determine the best technique?
The anesthetic techniques chosen for a particular case will depend on the interplay between the physiologic needs of each patient, the type of procedure, the skills and judgment of the anesthetic team, and the skills and judgment of the surgical team. Minimally-invasive cases lend themselves more to monitored anesthesia care. Open fetal cases are more commonly managed with general endotracheal anesthesia and high-dose volatile anesthetic. Positioning for minimally-invasive cases depends primarily on the location of the placenta, as the surgeons must plan ultrasound, needle, and catheter trajectories to avoid injuring the placenta, umbilical vessels, and fetuses. Left uterine displacement is often possible, but sometimes lateral, and even supine position with no uterine displacement may be needed to access the area of interest. Open fetal surgery is performed supine with left uterine displacement.
While obstetric anesthesia is most commonly accomplished with regional anesthetic techniques, the additional requirements of fetal surgery often preclude regional anesthesia as the sole technique. Epidural anesthesia alone may be sufficient for a brief, uncomplicated open fetal procedure, but the uterus must be relaxed, and if volatile anesthetic is not used, nitroglycerin is often the alternative of choice. In open fetal surgical cases, preoperatively a placed epidural may be used for postoperative analgesia.
Better analgesia after open fetal surgery is possible with epidural infusions than with intravenous patient-controlled analgesia. The incision usually made in open fetal surgery is a broad transverse incision inferior to the umbilicus but superior to the typical Pfannenstiel incision. Some practitioners feel clinically that better analgesia will decrease the chances of preterm labor. Epidural analgesia is typically combined with general endotracheal anesthesia.
If the epidural is used as the primary technique in an uncomplicated open fetal procedure, a potential benefit is realized by avoiding general anesthesia and intubation in a pregnant patient.
For postoperative analgesia alone, the usual risks of epidural catheter placement are the only drawbacks of this technique. It is, however, not a necessity for the management of postoperative pain.
If the epidural is used as the primary technique in an open fetal procedure, sedation in the pregnant patient must be avoided or kept to a minimum to minimize chances of aspiration. These cases often take several hours in total, and procedures of this length in the supine position with a left tilt may not be tolerated by the mother.
The surgical team must be comfortable with the mother being awake as they operate on the critically ill fetus.
Excessive patient motion will be poorly tolerated by the surgical team.
Oxygenation and ventilation cannot be controlled as precisely if the patient is not intubated.
Patient morbidity is likely to be greater if the patient were to need emergent intubation in the middle of the case, as compared to a controlled induction and intubation at the beginning of a case.
The epidural, if placed for postoperative analgesia, should not be used intraoperatively. The high-dose volatile anesthetic very commonly causes hypotension that requires vasopressor administration. Adding an epidural sympathectomy to this situation will needlessly complicate the hemodynamic management. Toward the end of the case, as the fetal surgery is complete, the volatile anesthetic is weaned, and the epidural can be dosed.
Combined general and epidural anesthesia is most commonly used for open fetal surgery. High-dose volatile anesthetic is the hallmark of these cases. It is used to minimize uterine tone to allow greater blood flow from the uterine vessels to the placenta (decreased uterine vascular resistance), and better surgical exposure. A relaxed uterus will be less likely to contract when hysterotomy is made, and it will also be able to hold a greater volume of amniotic fluid, which will keep the umbilical cord from getting compressed. Occlusion of the umbilical cord can be catastrophic.
High-dose volatile anesthetic will cause some degree of hypotension in all patients. Maternal hypotension will decrease fetal oxygen delivery. The hypotension should be treated with vasopressors or intravenous fluids but the volatile anesthetic should not be decreased as the uterine tone will increase. Some minimally-invasive cases, such as fetal cardiac catheterization, may also be better served by a general anesthetic. These cases, however, do not require high-dose volatile as do the open fetal cases. The uterus is accessed by smaller instruments. No hysterotomy is required, and problems with intraoperative contractions are less likely.
The patients should be quite still as the operative team is passing needles and catheters through the maternal abdomen, into the uterus, directly through the fetal chest wall and myocardium to access the fetal heart valves or atrial septum as needed.
Uterine tone is quite easily managed with volatile anesthetics.
These cases are quite complex to begin with, and early definitive control of the airway allows the teams to focus on the many other issues at hand.
Precise control of ventilation and oxygenation is easier.
The patient can be rendered completely motionless, which will likely aid the surgical team in cases where there is little room for error (e.g., cardiac catheterization, pulmonary lobectomy, tracheostomy, or myelomeningocele closure).
The pregnant patient is subjected to the risks of general anesthesia.
Prolonged exposure to high-dose volatile anesthetic does cause fetal cardiac dysfunction.
The toxicity of anesthetic agents to the developing brain is a subject of much discussion and research, and their effects on the fetal brain remain to be further elucidated.
The pregnant patient is at a higher risk for difficulty with intubation. Smaller endotracheal tubes and difficult airway equipment should be available. If the airway is judged to be difficult preoperatively, consideration should be given to awake intubation.
Monitored anesthesia care
Monitored anesthesia care (MAC) is the most commonly used technique for the majority of minimally-invasive cases. Minimally-invasive cases are often not painful enough to the mother to require neuraxial anesthesia. The instruments are quite small, and local anesthetic infiltration suffices. The unique factor here is the need to make the fetus or fetuses as motionless as possible to allow delicate laser surgery on placental vessels or insertion of needles and catheters into the fetal bladder or thorax. The mother is often given intravenous medication to decrease fetal movement, which then escalates care of the mother from a “local anesthesia case” to “MAC.”
Well-conducted MAC avoids the risks of general anesthesia in a pregnant patient.
MAC allows for quick recovery and patients are quite satisfied after the experience.
Sedation must be carried out carefully because of the risk for aspiration is increased in a pregnant patient.
These cases are typically performed quite early in gestation (16 weeks’ gestation to mid 20 weeks). If a case is planned for later in gestation, the team must consider the increased risk of aspiration, and may consider a general anesthetic.
Successful MAC is contingent on the surgeons expeditiously and skillfully doing what they need to do. If there is doubt or unfamiliarity in any members of the team, a general anesthetic may be considered.
Patient positioning can be challenging and quite variable for these cases. The patients should be awake enough to participate in their own positioning to ensure comfort.
6. What is the author's preferred anesthesia technique and why?
Unless the patient must remain completely immobile, MAC is well accepted by the patients, anesthesiologist, and surgeons at our institution. MAC can be accomplished with any of a variety of options. Traditional regimens have included combinations of morphine and diazepam, each on the order of 10 to 20 mg. This may leave patients quite sedated and nauseated in the postoperative period.
After aspiration prophylaxis with ranitidine and sodium bicarbonate, my preference is to start a remifentanil infusion (no bolus) at a rate of 0.1 mg/kg/min, once the patient has had monitors attached and been positioned supine with left uterine displacement. A 100% non-rebreathing facemask is applied. The surgeons will begin with a preoperative ultrasound, and at this time, I will give a 2-3 mg bolus of midazolam.
The patients are slightly sedated, but all are conversant and able to help with their own positioning should this be deemed necessary after the preparatory ultrasound. The remifentanil may be titrated up and down as needed, but in my experience this is rare. The surgeons will inject local anesthetic at their insertion point. If the case proceeds for more than 1 hour, redosing the midazolamin in small increments (0.5-1 mg) may be done. When the procedure is completed, the remifentanil is stopped, and the patients move themselves from the OR table to their bed. Other practitioners have had success with propofol or dexmedetomidine infusions, or combinations of midazolam and fentanyl.
Remifentanil has been shown to optimize surgical conditions and decrease fetal movement in these cases.
Open mid-gestation cases
A high lumbar or low thoracic epidural is placed preoperatively. It is tested, but it is not bolused with local anesthetic until the end of the case. After aspiration prophylaxis and left uterine displacement, the patient is intubated after rapid sequence induction of general anesthesia. A second large bore IV is placed because of the possibility of rapid bleeding from the hysterotomy site with high-dose volatile anesthetic.
A radial arterial catheter is placed for invasive blood pressure monitoring. Tight blood pressure control is crucial in these cases. If maternal blood pressure drops, uteroplacental perfusion will decrease and the fetus may suffer. These cases are often done with at least intermittent, if not continuous fetal echocardiography and decreased contractility and fetal bradycardia have been noted with decreased maternal blood pressure. The blood pressure is maintained with a goal of being within 10-20% of baseline. Barring other uteroplacental or umbilical cord problems, the fetal heart rate is a very sensitive indicator of the need to increase the maternal blood pressure.
High-dose desflurane (14-18% expired concentration) is started after the uterus is exposed. Intravenous fluids are minimized, with a goal of 500-1000 ml of crystalloid total for the case. These patients are at high risk for postoperative pulmonary edema. Because of the high dose volatile agent, minimal IV fluid administration, and the potential for aortocaval compression, blood pressure management during these cases can be challenging. Phenylephrine infusions are started soon after induction, as the additional venous and arterial access are obtained. Boluses of phenylephrine and ephedrine are also given, with maternal heart rate guiding the choice of vasopressor.
Some cases will call for fetal pulse oximetry and fetal peripheral intravenous access. Typical cases would include a midgestation sacrococcygeal teratoma resection or pulmonary lobectomy. The most common open mid gestation cases are closure of myelomeningocele, and unless bleeding is expected, these cases usually do not warrant a fetal IV.
The fetus will get an intramuscular injection of 20mcg/kg of fentanyl, 20 mcg/kg atropine, and 0.2 mg/kg vecuronium. The dosing is based on estimated fetal weight from ultrasound.
After the fetus is replaced in the uterus and it is getting closed, I will consult with the surgeons and start a magnesium sulfate bolus of 6g over 20 minutes. After the bolus is completed, an infusion is run at 4g/hr.
During uterine and abdominal closure, the anesthesiologist must perform a balancing act of running in the magnesium bolus, decreasing the volatile anesthetic, dosing the epidural and weaning the vasopressor infusion.
These cases are typically performed around 23-26 weeks’ gestation. Although technically the fetus is viable, resuscitation for fetal distress will not involve delivery and operating on the fetus in another operating room. Any intraoperative fetal resuscitation will be performed only while the fetus is still attached to the mother.
These cases start in a similar fashion with aspiration prophylaxis, epidural, rapid sequence induction, large IVs, arterial line, high-dose volatile and vasopressor administration.
At the beginning of the case, the surgeons will hand off a sterile pulse oximeter cable, oxygen, and IV tubing from the sterile field to allow for intraoperative fetal pulse oximetry, IV placement, and ventilation at the end of the procedure.
The fetus will also get an intramuscular injection of fentanyl, atropine, and vecuronium.
A key difference is that this case is performed late in gestation, with the goal of delivering a child who is close to term at the end of the procedure. As such, a team of neonatologists should be prepared to receive the newborn after the surgery and complete the neonatal resuscitation. Additionally, because the child will be born at a viable gestational age, a second anesthesia and surgical nursing team should be prepared in another operating room should the baby not tolerate the EXIT procedure and resuscitation is not successful with the baby still attached to the mother. This may happen, for example, if intraoperative placental abruption occurred. If resuscitation is successful, the surgery may be completed in the second operating room.
These mothers do not have as great a risk for post operative pulmonary edema, so intravenous fluid administration may be more aggressive. A typical EXIT procedure patient will receive 3-5 liters of crystalloid.
After the fetal procedure is completed (tracheostomy, neck tumor excision, intubation, pulmonary lobectomy), the fetus is ventilated. Endotracheal intubation can be confirmed by a chest rise and an increase in fetal oxygen saturation. Once this is confirmed, the umbilical cord is cut and the child is taken to the neonatal team.
After the umbilical cord is cut, pitocin is given, and the volatile agent is rapidly discontinued. Methergine and carboprost may be used to help improve uterine tone after the prolonged exposure to volatile anesthetic. Vasopressor infusions may often be weaned at this time.
The epidural is bolused at the end of the case.
What prophylactic antibiotics should be administered?
There is no Surgical Care Improvement Project (SCIP) recommendation for fetal surgery. Our institution typically administers cefazolin 30 mg/kg to a maximum of 2 g. This is in line with SCIP guidelines for hysterectomy from 2014. It is our surgical practice to instill 2 g oxacillin into the amniotic fluid at the end of the case.
What do I need to know about the surgical technique to optimize my anesthetic care?
The position of the placenta will determine where the surgical access to the uterus will be. If the placenta has implanted on the posterior aspect of the uterus, then the access be from the anterior abdominal wall with straight instruments. Positioning the patient is easier, but sometimes the fetus will be laying on the placental vessels of interest. If the placenta is implanted on the anterior aspect of the uterus, the patient may be tilted almost lateral, the access to the uterus will be form the lateral aspects of the abdominal wall with curved instruments. This may be more painful, but the fetus is more likely to be suspended in the amniotic fluid and the surgeons may have an easier time getting to the placental vessels.
Open mid-gestation cases
The stages of the procedure include laparotomy, uterine exposure, and ultrasound to determine placental edges. If the placenta is anteriorly implanted, the uterus must be completely exteriorized to allow for hysterotomy on the posterior aspect of the uterus. The uterus may remain in the abdomen if the placenta is posterior. The hysterotomy is carefully made, avoiding the edge of the placenta, and uterine staples are used to minimize bleeding. Warmed crystalloid is infused into the amniotic sac to keep up amniotic fluid volume and warm the fetus. If the uterus is completely exteriorized, maintenance of maternal blood pressure is often easier as aortocaval compression is no longer an issue.
The area of interest of the fetus is exposed (myelomeningocele, thorax, sacrococcygeal teratoma, etc.). A pulse oximeter and and IV may be placed in the fetus. An intramuscular injection is given to the fetus, and surgery on the fetus proceeds.
After completion of the procedure, pulse oximeter and IV are removed, and the fetus is returned to the uterus.
The first stages of an EXIT are similar to open mid-gestation surgery.
After the fetus is exposed and the intramuscular injection is given, the pulse oximeter and IV are typically placed, and surgery starts. If the pathology is airway related, it may involve fetal laryngoscopy, bronchoscopy, or tracheostomy. The airway is secured as soon as possible. If the procedure involves the lungs, the fetus is intubated before the thoracotomy proceeds. The fetus is not ventilated until the end of the case, so as not to start the transitional circulation until necessary. The main idea of these cases is the use of the placenta as “bypass” so the fetal circulation is maintained as long as possible.
What can I do intraoperatively to assist the surgeon and optimize patient care?
Abdominal motion during maternal breathing may give the surgeons a moving target. Asking the surgeons for notice before critical actions, and asking the patient to hold her breath at these times, is helpful.
Some cases require infusion of warmed crystalloid into the amniotic sac. Keep close track of the fluid going in and out of the patient, as pulmonary edema has occurred during minimally-invasive surgery also.
While the fetuses are sick, fetal bradycardia and distress do not often occur except in cases of fetal cardiac catheterization.
Emergency doses of atropine and epinephrine should be available and can be given via intracardiac injection.
Understanding the whole surgical plan and approach is of great benefit in these cases.
Open mid-gestation case
Uterine tone must be low before the hysterotomy is made. Rapid bleeding may occur if the uterine stapling device does not fire correctly, so the anesthesia team must be vigilant.
Boluses of nitroglycerin 20-40 mcg at a time can help decrease uterine tone if the volatile anesthetic cannot be increased any more.
If a thoracotomy is made, the team must be vigilant when the diseased lung is delivered from the chest. There is a relatively high likelihood of fetal bradycardia as the formerly compressed heart and shifted mediastinum are decompressed. Extra fetal intravenous fluid loading (10-20 mL/kg using estimated fetal weight) or preemptive transfusion has seemed to help.
The actions to help for an EXIT are largely similar to those for a mid-gestation case.
Since the fetus will have an IV and possibly be transfused with blood, it is helpful to define one IV pole specifically for the fetus. This will also make things easier if the fetus must go emergently to another room. The IV pole can be easily wheeled to the other OR without having to disconnect and untangle the cables and lines.
What are the most common intraoperative complications and how can they be avoided/treated?
Ensure left uterine displacement.
If hypovolemia or bleeding is likely, intravenous crystalloid or blood are warranted. The team must be cautious with fluid administration in open mid-gestation cases.
Phenylephrine and ephedrine can also be used to treat hypotension that is often due to high-dose volatile anesthetic.
Decreasing the volatile anesthetic may result in unwanted increases in uterine tone with resulting decreases in fetal perfusion, loss of amniotic fluid, and placental separation.
Hypotension should be treated promptly, as the fetus is very sensitive to decreased perfusion.
Diagnosis and treatment of the usual causes of hypoxia in anesthetized patient is the first step.
Occasionally the patients oxygen saturations will decrease with the high-dose volatile anesthetic, this may be due to loss of hypoxic pulmonary vasoconstriction. This is usually mild enough to be easily treated with an increase in inspired oxygen concentration.
Pulmonary edema may occur in open mid-gestation cases, although this is more likely in the postoperative period than the intraoperative period.
Aspiration risk should be minimized with preoperative aspiration prophylaxis and, if intubation is planned, a rapid sequence induction of general anesthesia.
Vigilance during the initial hysterotomy and uterine stapling is key, but the team must be aware at all times.
Packed red blood cells should be at hand to be transfused if bleeding is rapid and cannot be controlled. Two to four units should be crossmatched.
Fetal blood loss is hard to assess, given the confounding factors of amniotic fluid and maternal blood. Fetal echocardiography can help assess cardiac filling, and while only rarely done, blood gases and hemoglobin can be determined from umbilical samples. O negative blood should be crossmatched against the maternal blood sample.
Normal fetal pulse oximetry ranges from 40-70%.
Normal fetal heart rate ranges from 120-160.
If either the fetal oxygen saturation or heart rate decreases, the anesthesia team must first ensure that the mother is stable and her physiology optimized (oxygenation, ventilation, blood pressure, hemoglobin concentration, etc.).
Maternal hypotension is the most common reason for a fetal bradycardia, so the team should optimize maternal blood pressure with fluids or vasopressors.
An obstetrician must ensure that there is adequate amniotic fluid volume, the fetus is warm and well-positioned, and the umbilical cord is not compressed or kinked.
The team must also keep in mind the possibility of occult placental abruption. This can be assessed with the obstetric ultrasound.
Emergency doses of atropine and epinephrine should be available and given sterilely to the scrub nurses for potential IM or umbilical vessel administration.
As above, the mother’s health and safety must be ensured.
Optimize her physiology to deliver oxygen to the fetus.
Begin chest compressions on the sterile field. The efficacy of the compressions can be monitored by fetal echocardiography.
Administer doses of atropine and epinephrine to temporize.
Search for the cause of the bradycardia and treat it.
b. If the patient is intubated, are there any special criteria for extubation?
The patient should be extubated awake.
c. Postoperative management
What analgesic modalities can I implement?
Postoperative analgesia is easily managed with oral medications after minimally-invasive cases.
After open fetal surgery, continuous epidural infusion of local anesthetic is commonly used. The epidural is usually removed on postoperative day 2. A low-dose local anesthetic and opioid combination works well. Our institution uses 0.1% ropivacaine with 2 mcg/mL fentanyl for patient controlled epidural analgesia.
What level bed acuity is appropriate?
The patients should return to a labor and delivery unit for fetal and maternal monitoring. Postoperative nursing protocols must be clearly defined. Intensive care at experienced centers is not usually necessary unless the practitioners have increased concerns for pulmonary edema, or there was a complicated intraoperative course.
What are common postoperative complications, and ways to prevent and treat them?
Most postoperative complications are surgical in nature and include preterm labor, chorioamniotic membrane separation, oligohydramnios.
Pulmonary edema may be treated with oxygen and diuretics. If it is severe enough, intubation with mechanical ventilation may be necessary.
Oliguria resulting from hypovolemia may be treated carefully with intravenous fluid administration. Invasive monitoring can certainly be considered, but is rarely needed.
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- What the Anesthesiologist Should Know before the Operative Procedure
- 1. What is the urgency of the surgery?
- What is the risk of delay in order to obtain additional preoperative information?
- 2. Preoperative evaluation
- 3. What are the implications of co-existing disease on perioperative care?
- b. Cardiovascular system
- c. Pulmonary
- d. Renal-GI
- e. Neurologic
- f. Endocrine
- g. Additional systems/conditions which may be of concern in a patient undergoing this procedure and are relevant for the anesthetic plan (e.g., musculoskeletal in orthopedic procedures, hematologic in a cancer patient)
- 4. What are the patient's medications and how should they be managed in the perioperative period?
- h. Are there medications commonly seen in patients undergoing this procedure and for which should there be greater concern?
- i. What should be recommended with regard to continuation of medications taken chronically?
- j. How to modify care for patients with known allergies:
- k. Latex allergy - If the patient has a sensitivity to latex (e.g., rash from gloves, underwear, etc.) versus anaphylactic reaction, prepare the operating room with latex-free products.
- l. Does the patient have any antibiotic allergies? [Common antibiotic allergies and alternative antibiotics]
- m. Does the patient have a history of allergy to anesthesia?
- 5. What laboratory tests should be obtained and has everything been reviewed?
- Intraoperative Management: What are the options for anesthetic management and how to determine the best technique?
- 6. What is the author's preferred anesthesia technique and why?
- Minimally-invasive cases
- Open mid-gestation cases
- EXIT procedures
- What prophylactic antibiotics should be administered?
- What do I need to know about the surgical technique to optimize my anesthetic care?
- What can I do intraoperatively to assist the surgeon and optimize patient care?
- What are the most common intraoperative complications and how can they be avoided/treated?
- a. Neurologic
- b. If the patient is intubated, are there any special criteria for extubation?
- c. Postoperative management