Anesthesiology

Fetal surgery/EXIT procedures/anesthesia for TTTS

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What the Anesthesiologist Should Know before the Operative Procedure

Fetal surgery and anesthesia for fetal surgery are branches of obstetric anesthesia. This form of anesthesia is complicated because anesthetic care is being provided for two patients, mother and fetus simultaneously. The mother of the fetus is essentially being used as a life support system for the fetus, permitting a major fetal surgical intervention that would otherwise place the fetus at an increased risk for morbidity or mortality.

The anesthetic provided to the mother is simultaneously being imparted to the fetus, thus the side effect profile of the anesthetic must be considered safe for both patients. The primary anesthetic goal for fetal surgery is to provide a smooth maternal anesthetic that produces: 1) maternal cardiovascular (CV) stability 2) minimal maternal pulmonary and ventilatory compromise 3) uterine relaxation 4) tocolysis while not causing significant derangements in maternal placental perfusion or fetal cardiovascular stability.

Fetal surgery is undertaken when a congenital defect, malformation or illness will confer significant morbidity and/or mortality to the fetus following birth. The criteria required to undergo fetal surgical intervention necessitates that significant risk for death or severe morbidity exists to the fetus from a solitary and repairable defect. Additionally, there needs to be minimal risk of subsequent harm to the mother of the fetus from the surgical intervention.

A difficult situation may arise when the mother of the fetus has significant medical co-morbidities increasing her risk as a candidate for anesthesia for fetal surgery. Such situations require a detailed risk/benefit review to be conducted by a multidisciplinary team including the anesthesiologist, the surgeon, and obstetrician, plus a neonatologist to represent the fetus, and an internist to represent the mother. Significant maternal medical comorbidities can provide enough increased risk to mother and fetus to eliminate potential fetal surgical correction.

Three subtypes of fetal surgery exist. Each variation introduces unique requirements to the anesthetic. The delineations of the three different subtypes depend on: 1) the timing of the surgical procedure during the pregnancy 2) the extent of the uterine incision and 3) the disposition of the fetus following the surgical repair.

Option #1: Open fetal surgery

Open fetal surgery is completed for fetal diseases that must be repaired earlier in the pregnancy to allow further time for appropriate organ development after the surgical repair. Such a repair will occur between the 18th and 32nd week and necessitates a large superior uterine incision and the exteriorization of the fetus for surgical repair while maintaining placental circulation. Following the completion of the repair the fetus will be replaced into the uterus allowing the pregnancy to progress.

Bed rest and continuous tocolytic therapy are required for the remainder of the pregnancy following such an intervention. Fetal lesions corrected in this manner are: CCAMs (congenital cystic adenomatoid malformations), bronchopulmonary sequestrations, occasional myelomeningocele, and sacrococcygeal teratoma. In all of these situations, non-removal of the lesion would lead to severe malformation of either the pulmonary tree or the central nervous system, and thus lead to significant morbitiy or mortality.

Option #2: EXIT procedure

The EXIT (ex utero intrapartum treatment) procedure is an option for completing a potentially life-threatening intervention at delivery while using the uteroplacental circulation as a cardiopulmonary bypass system. Frequently the procedure in question will be the management of a fetal airway in a fetus with a suspected airway issue. The procedure requires a C-section and hysterotomy where the fetus is accessed and the required procedure is completed.

In the case of an intubation the maintenance of the uteroplacental circulation allows additional time to manage a difficult airway without concerns for derangements in the fetal oxygenation and ventilation. Such interventions are completed near term and once the procedure is completed the C-section will progress and the fetus will be delivered. In essence this is a scheduled C-section with a delay in the middle. The reasons for completing this procedure are congenital or iatrogenic high airway obstructions, tumor resections for a potentially obstructing fetal neck mass or other lesion that may prevent airway patency following delivery.

Due to the overall increased complexity, combined with an increased maternal risk and occasionally equivocal fetal benefit, open fetal surgery cases continue to require very specific indications to proceed. Recent studies of the different variations of fetal surgery find the EXIT procedure is being utilized for an ever growing list of indications with increasing frequency.

Option #3: Fetoscopic surgery

Fetoscopic surgery is the minimally invasive version of fetal surgery. In some cases the procedure is not surgical but an intervention to prevent an ongoing issue with a fetus, which, if not resolved, might lead to an increased risk for morbidity or mortality of the fetus. These interventions occur midgestation and only require small incisions in the abdominal wall and the uterus for trocar/instrument placement, similar to laparoscopic abdominal surgery. Following the completion of fetoscopic surgery the pregnancy is allowed to progress to near term when a C-section will be performed. Indications for this type of fetal surgery include: twin-twin transfusion syndrome (TTTS), twin reversed arterial perfusion sequence, and bladder outlet obstruction.

1. What is the urgency of the surgery?

What is the risk of delay in order to obtain additional preoperative information?

Open fetal surgery is completed on an elective basis under very controlled circumstances. Optimal patient circumstances are required for both the mother of the fetus and the fetus itself to provide for the best potential outcome. All precautions should be taken to avoid completing such an intervention under hasty or rushed circumstances; too many details may be missed.

Occasionally fetoscopic surgery may be required in an urgent manner should the diagnosis of TTTS or twin reversed transfusion perfusion sequence be recognized. In order for such a diagnosis to be made, one of the twins needs to be in an already compromised state, thus creating the sense of urgency.

Emergent:Should rarely if ever occur. Under such circumstances the mother of the fetus must be exceptionally healthy with a noncomplicated pregnancy. Most importantly, to give informed consent the mother must be competent and aware of the number and scope potential complications to either her or the fetus or both, including but not limited to fetal demise, possible hysterectomy and/or her own demise.

Urgent: Fetoscopic blood transfusions in certain situations can occur in an urgent manner. Similar criteria must be met as noted above for an emergent scenario, including optimization of any medical comorbidities, a noncomplicated pregnancy, and completion of informed consent by the mother of the fetus.

Elective: The majority of all fetal surgical interventions will be conducted in this manner. Fetal surgical interventions are high risk at baseline and need to be thoroughly planned and carefully choreographed. All potential complications need to be addressed and managed in advance. The potential maternal, fetal and maternal/fetal risk is significant enough to warrant that no detail be overlooked.

2. Preoperative evaluation

The main focus here is maternal health and surgical preparation. Most women of child-bearing age are healthy. However, pregnant patients have unique preoperative risks that require addressing. Obstetric anesthesiologists attempt to utilize neuraxial anesthesia to mitigate elevated risks associated with general anesthesia in a parturient. Unfortunately, fetal surgery requiring a hysterotomy necessitates significant uterine relaxation, and uterine tone is not affected by neuraxial anesthesia. General anesthesia utilizing high doses of volatile agent (2.0 MAC [minumum alveolar concentration]) as a reasonable mechanism for producing sufficient uterine relaxation.

The parturient will require a pre-operative evaluation focused on preparing a parturient for general anesthesia. Evaluation of cardiac function is a priority. Although unusual in this age group, any concern for altered CV performance necessitates detailed evaluation: ECG (electrocardiogram), echocardiogram and cardiology evaluation if concern is high. Close attention needs to be paid to normalizing maternal hemoglobin and hematocrit concentrations. Decreased H/H values can compromise oxygen delivering capacity, inducing hypoxemia in the fetus.

Polyhydramnios is a maternal condition often associated with congenital anomalies being treated with fetal surgery such as situations where the fetal airway or esophageal function are compromised. When present, polyhydramnios increases maternal risk during fetal surgery. Should the polyhydramnios become severe it may require percutaneous fluid removal before proceeding with the fetal surgical intervention.

Pulmonary reserves are altered in parturients due to decreased FRC from cephalad uterine displacement of intraabdominal contents. Increased oxygen requirements and decreased FRC usually produce a respiratory pattern of a decreased tidal volume and increased respiratory rate resulting in elevated minute ventilation.

These alterations are important to the anesthesiologist because they alter blood gases and produce decreased pulmonary reserves. This is illustrated by precipitous decline in SpO2 (saturation of peripheral oxygen) levels with hypoventilation or apnea. The lack of pulmonary reserve highlights one of the most concerning aspects of completing a general anesthetic in a parturient, airway management. Pregnancy induced anatomical changes to the airway include 1) increase in redundant airway soft tissue, 2) increased edema of the soft tissue, and 3) increasing abdominal girth and breast size, all of which may complicate endotracheal intubation.

Multiple alterations to the GI system further increase the potential for aspiration and subsequent chemical pneumonitis during manipulation of the airway. Abdominal content displacement occurs due to the presence of the expanding uterus, which alters the normal anatomical position of the GE junction to the diaphragm. The loss of this relationship, in addition to potentially delayed gastric emptying produces an elevated risk for regurgitation and aspiration during anesthetic induction and direct laryngoscopy.

During fetal surgical procedures the mother's tolerance for the anesthetic and subsequent surgical procedure will affect the outcome of the fetus. Maternal compromise will lead to potentially unrecoverable fetal compromise.

Recommendations for fetal preoperative examination include multiple imaging exams to characterize the lesion in question while ensuring no additional congenital anomalies exist. Repeat a detailed fetal ultrasound and ultrafast magnetic resonance imaging (MRI) to further categorize the defect to be repaired and to look in detail for other anomalies that might eliminate fetal surgery as a corrective option. Fetal cardiac echocardiography evaluation will ensure that no additional cardiac anomolies exist. A fetal blood sample or amniocentesis will be sent for genetic analysis.

  • Although highly unusual in this population, medically unstable conditions warranting further evaluation include signs of CV compromise including congestive heart failure (CHF), shock, hypovolemia, rhythm or valvular disturbances or signs of compromised coronary artery perfusion. Signs of preeclampsia necessitate detailed evaluation of the mother followed by aggressive blood pressure (BP)/preeclampsia management if appropriate. Signs/symptoms of altered pulmonary function including the presence and severity of RAD or recent URI may necessitate delay.

  • Close attention should be given to ensuring that normal coagulation exists, including the lack of any signs or symptoms consistent with hepatic dysfunction or HELLP syndrome. Maternal gestational diabetes will require careful management. Any or all of the above conditions may or may not disqualify the patient from fetal surgical options depending on the how the mother responds to various management options.

  • Delaying surgery may be indicated for maternal complications with various organ systems that are not responding appropriately to treatment.

  • Contraindication to surgery: Maternal mirror syndrome is a scenario affecting both mother and fetus. High cardiac output in the fetus produces hydrops fetalis. As this situation progresses the placenta becomes engorged, eliciting the release of placental stress hormones, proteins, and peptides. These products are released into the maternal ciriculation leading to maternal development of signs and symptoms of preeclampsia. This not only presents fetal concern, but now maternal compromise takes precedence. Treatment requires fetal and placental delivery, even if the fetus is nonviable. Attempts to repair the fetal anatomical derangements that led to this sequence of events will not improve the developing maternal illness.

3. What are the implications of co-existing disease on perioperative care?

As stated above, coexisting disease in the parturient is rare. To qualify for a fetal procedure, the mother of the fetus needs to be healthy at baseline. Similarly, the fetus cannot have multiple congenital issues that will continue to place the fetus at risk of morbidity or mortality at birth even if the surgical repair is successful.

Perioperative evaluation

Review the history and physical for mother and fetus that will have been performed by the obstetrician and fetal surgeon. Ensure that any concerning or missing pre-operative data has been obtained and evaluated. Review current lab values such as hemoglobin and hematocrit, recent electrolyte panel with special attention to potassium levels or altered bicarbonate levels and any signs of abnormal renal function. Consider 24-hour urine creatinine collection and protein levels if maternal hypertension is present.

Perioperative risk reduction strategies

Extensive preoperative evaluation and subsequent follow up and correction of issues should have been done by the maternal-fetal medicine obstetric team. Minimal perioperative management of comorbidites should be necessary. If warranted, consider rescheduling the procedure until the maternal condition is optimized.

b. Cardiovascular system

Acute/unstable conditions are rarely an issue in this patient population. Concerns for cardiac ischemia would eliminate a mother as a potential candidate for this type of procedure. During the actual procedure, deviation of maternal MAP should vary less than 10%. The use of either ephedrine 5-10 mg IV or phenylephrine 50-100 mcg/kg IV to maintain stable MAP is indicated.

c. Pulmonary

Chronic obstructive pulmonary disease (COPD): Rarely an issue in this patient population. Should a patient for fetal surgery have symptomatic COPD, it would require pulmonary function tests and determining the responsiveness to bronchodilator therapy. Should a patient present with severe COPD or nonresponsive COPD then fetal surgery may present too much maternal risk to proceed.

Reactive airway disease (asthma): Fetal surgical interventions are usually not performed in an emergent or urgent manner; therefore, the opportunity exists for the optimization of the mother's asthma management.

d. Renal-GI:

Preeclampsia requires renal function tests and aggressive management. If the condition does not respond to therapy this may be a contraindication to proceeding with surgery. Mirror syndrome (Ballantine syndrome) as described above is a condition associated with sacrococcygeal teratoma (SCT) where the mother of the fetus becomes ill due to fetal decline. This syndrome is believed to be caused by a release of placental vasoactive factors or toxins from an engorged placenta caused by compression from the SCT. The definitive treatment for this condition is to deliver the fetus. Surgical excision of the SCT will not resolve these symptoms.

e. Neurologic:

Maternal neurologic conditions are usually not an issue in this patient population. Of particular concern would be the presence of an intracranial lesion (i.e., arteriovenous malformation [AVM]) that might limit the ability of the mother of the fetus to tolerate fluctuations in blood pressure while maintaining cerebral perfusion pressure. Maternal seizure disorders, if not adequately controlled, might eliminate the possibility of intrauterine fetal surgery.

Acute issues:Any elevated intracranial pressure, alterations in mental status, poorly controlled seizure disorder, or substance abuse by the mother would probably be a contraindication for surgery.

Chronic disease:The presence of any unstable intracranial vascular lesion that may be worsened by changes in cerebral perfusion pressure would be a contraindication.

f. Endocrine:

Gestational diabetes

The main perioperative issue here is reasonable glucose control in the perioperative setting. Primary goal: avoid perioperative hypoglycemia. Secondary goal: treat and manage elevations in blood glucose levels. Overcorrection producing hypoglycemia is more concerning than a brief period of mild hyperglycemia during the intraoperative period.

Other potential endocrine issues

  • Thyroid disease

Hyperthyroidism may add significant risk and complicate the subsequent anesthetic. Hypothyroidism may delay emergence from general anesthesia. Euthyroidism is a necessary preoperative goal for such a complicated and risky procedure. However reaching euthyroidism takes time, thus if the mother of the fetus is not well controlled at the time of the fetal diagnosis, this may become a contraindication to fetal surgery. The situation needs to be evaluated on a case-by-case basis.

  • Adrenal disease

If the mother is symptomatic for either hypo or hyper adrenalism at the time of diagnosis, the mother of the fetus may no longer qualify for fetal surgery due to a significantly increase risk for general anesthesia under such circumstances.

g. Additional systems/conditions which may be of concern in a patient undergoing this procedure and are relevant for the anesthetic plan (eg. musculoskeletal in orthopedic procedures, hematologic in a cancer patient)

Manipulation of uterine tone is a major consideration. Following the intraoperative hysterotomy and during the fetal surgery, uterine contractions must be actively prevented and/or repressed. Intraoperatively, 1.5 to 2 MAC of volatile anesthetic can reliably produce uterine relaxation. Once the need for uterine relaxation is over, volatile anesthetics can be decreased or even discontinued completely if a lumbar epidural was placed prior to incision (optimal choice) and amnesia can be provided by other methods. The anesthesiologist is balancing the need to prevent preterm labor with the need to prevent uterine atony and hemorrhage if delivery has occurred.

Tocolysis

  • Preoperative

Administer oral or rectal indomethacin. This will be continued post operatively every 6 hours for 2 days. Due to potential fetal side effects, post operative fetal ultrasounds are required every other day to evaluate ductal patency, cardiac function and amniotic fluid volume.

  • At closure of the hysterotomy

Start intravenous (IV) magnesium sulfate infusion (recommend 6 g IV load with 2-4 g/h thereafter). Monitor magnesium serum levels as needed based on clinical exam for magnesium toxicity.

  • Two days post procedure

If uterine contractions are well controlled, consider transitioning to oral tocolysis with oral nifedipine 10-20 mg twice daily. Monitor closely for uterine contractions.

Completing the EXIT procedure: This is a complicated transition from uterine relaxation for the fetal procedure to a rapid return of uterine tone to prevent uterine atony and postpartum hemorrhage following the delivery of the placenta. Several oxytocics should be available.

  • Oxytocin infusion: 20 units in 500 mL infused over 30 minutes immediately following the delivery of the placenta, followed by 10-40 units in 1000-mL bag over the next 8 hours.

  • Hemabate 250 mcg (prostaglandin F2-alpha) and methergine 0.2 mg administered via intramuscular or intrauterine injection, in addition to direct fundal massage, are second-line therapies to be used to reverse refractory uterine atony after delivery of the fetus.

Of note: due to the potential of developing refractory uterine atony, the need for emergent hysterectomy should be discussed at length with the mother of the fetus before starting the procedure.

4. What are the patient's medications and how should they be managed in the perioperative period?

  • Prenatal vitamins can be held on the day of surgery if they induce nausea and vomiting when taken on an empty stomach.

  • Avoid nonsteroidal anti-inflammatory medications other than indomethacin for concerns for bleeding and uterine atony.

  • Long-acting Insulin administration should be held on the morning of surgery while NPO. Follow blood glucose levels and treat hypoglycemia with intravenous dextrose or clear juices (if more than 2 hours before surgery). Test glucose levels upon arrival to the recovery room. Intraoperatively correct hyperglycemia with caution. In the PACU, regular Insulin sliding scales may be used to guide insulin administration. Subcutaneous administration may be preferred over intravenous administration to prevent development of hypoglycemia.

  • Continue thyroid medication as ordered.

  • Asthma medications: Ask the patient about any acute changes or exacerbations of her asthma. Establish a baseline lung exam. Consider pretreatment with an albuterol nebulizer or even rescheduling the procedure if there is an acute exacerbation.

h. Are there medications commonly seen in patients undergoing this procedure and for which should there be greater concern?

Perioperative tocolysis is routinely used for these procedures.

i. What should be recommended with regard to continuation of medications taken chronically?

Cardiac: Continue antihypertensive medications.

Pulmonary: Continue asthma medications.

Neurologic: Continue seizure medications but be aware that some anticonvulsant therapies may inhibit coagulation and increase the potential for intraoperative blood loss.

Psychiatric: The presence of multiple or large doses of psychiatric medications might raise concern for the mother's ability to consent to the procedure and ability to follow postoperative requirements.

j. How To modify care for patients with known allergies -

Avoid medications related to the patient's allergies.

k. Latex allergy- If the patient has a sensitivity to latex (eg. rash from gloves, underwear, etc.) versus anaphylactic reaction, prepare the operating room with latex-free products.

To be safe in this high risk of environment, consider eliminating all latex products, even if patient is not believed to be allergic. This is especially true if the fetus has a neural tube defect.

l. Does the patient have any antibiotic allergies- [Common antibiotic allergies and alternative antibiotics]

Discuss alternate antibiotic coverage and dose with both the obstetric and pediatric surgical teams. Prepare correct dose in advance.

m. Does the patient have a history of allergy to anesthesia?

Due to the use of volatile anesthetics for uterine relaxation, a history of malignant hyperthermia (MH) susceptibility in the mother is important. If concerned, consider a complete TIVA (total intravenous anesthetic) technique, and discussion with the multidisciplinary team to determine alternate methods of tocolysis.

Malignant hyperthermia (MH)

Documented: Avoid all trigger agents such as succinylcholine and inhalational agents:

  • Proposed general anesthetic plan: TIVA with tocolytic-induced uterine relaxation.

  • Ensure MH cart is available/stocked. Ensure anesthesia machine has been properly decontaminated and cleaned and has no volatile agents attached to prevent error.

  • Place an arterial line and draw a preanesthesia baseline blood gas.

  • Family history or risk factors for MH: discuss the severity of the reactions and the degree of the relative. Ask the patient if she had any issues with previous anesthetics.

Local anesthetics/muscle relaxants

Avoid succinylcholine.

5. What laboratory tests should be obtained and has everything been reviewed?

Blood type and cross-match to ensure there is blood available and that there are no antibodies that might interfere with transfusion.

Hematologic: Complete blood count to review hemoglobin and hematocrit to ensure they are optimized and to establish a baseline for intaoperative monitoring. A hematocrit less than 30 requires investigation. Platelet count should also be reviewed for gestational thrombocytopenia.

Coagulation:Obtain PT, INR, and PTT for any signs of coagulopathy. The presence of an unrecognized coagulopathy may prove catastrophic if uterine atony occurs or hysterectomy is necessary.

Imaging:There will have been multiple imaging studies of the fetus.

Intraoperative Management: What are the options for anesthetic management and how to determine the best technique?

The anesthetic requirements for these procedures are: maternal anesthesia and analgesia, fetal anesthesia and analgesia, no movement of either patient and precise control of uterine tone. Neuraxial anesthesia may be used for postoperative analgesia, but in the case of fetal surgery, rapid manipulation of uterine tone is required. This is best accomplished using general anesthesia with high doses of volatile agent.

Utilizing a combination of both general and neuraxial anesthesia provides the best results in this surgical environment. Viewing these cases in stages provides perspective.

Stage I: Complete all preoperative assessments and review her labs. Check NPO status and discuss any recent changes in the pregnancy, medication, or possible illnesses that may have occurred since the last visit. Place a large-bore intravenous catheter. Premedicate with a clear antacid and and metoclopromide 10 mg IV. Place a lumbar epidural catheter, but do not dose beyond test dose.

Stage II: Proceed with general anesthesia. When the patient is supine, always maintain left lateral uterine displacement to prevent supine hypotension syndrome. Due to the pregnancy induced changes discussed earlier, a rapid sequence induction with cricoid pressure is warranted. Intubate the patient and maintain on 0.5 MAC of volatile agent with to 50% nitrous oxide. Treat any hypotension more than 10% below baseline with ephedrine or phenylephrine intravenously, depending on maternal heart rate.

Stage III: At the time of skin incision, stop nitrous oxide, increase the volatile agent administration from 0.5 MAC to 2.0 MAC. This will allow time for uterine relaxation to occur. Keep intravenous crystalloids to a minimum to prevent the development of pulmonary edema during the case. Monitor blood gases regularly. Recently published literature has implicated the use of increased levels of desflurane for long periods of time with fetal cardiac instability. A potential option is the use of nitroglycerin infusion to promote uterine relaxation, or using total intravenous anesthesia until uterine incision. Both options limit the use of volatile agents; however, with the loss of volatile anesthetic-induced uterine relaxation, the ability to rapidly titrate the level of uterine relaxation may be lost.

NOTE:

  • A number of animal and subsequent human studies have illustrated a potential link between maternal PaCO2 levels and placental circulation. Hyperventilating the mother of the fetus during a general anesthetic will produce hypocarbia, which decreases placental blood flow and can lead to fetal compromise. Maintaining normocarbia may prove beneficial during fetal surgery.

  • The fetal autonomic nervous system develops at different rates. Initially the parasympathetic nervous system develops much faster than the sympathetic nervous system. Thus, any fetal autonomic nervous system stimulation will increase vagal tone and cause bradycardia. One of the most frequent causes of this reaction is fetal hypoxia.

Stage IV: When the hysterotomy is completed, access to the fetus is obtained. If able, place a sterile pulse oximeter probe on a fetal extremity and cover to eliminate ambient light interference.

NOTE:Fetal SpO2 readings in a adequately oxygenated fetus will be between 40 and 60%.

Additional monitoring is obtained through sterile transthoracic echocardiographic evaluations of heart rate stroke volume, contractility, and volume status. Fetal analgesia and anesthesia are obtained by subcutaneous or intravenous administration of 20 mcg/kg fentanyl. Minimal fetal surgical blood loss will be tolerated. Overall, fetal blood volume is small, about 100 to 110 mL/kg; however, most patients undergoing fetal surgery will weigh less than 1 kg. Based on the small volume and immature autonomic compensatory reflexes, the fetus will be able to tolerate minimal blood loss before developing cardiovascular instability. Consider fetal IV placement for more extensive surgical procedure or if fetal blood loss is unavoidable.

Stage V: Once the fetal repair is complete and hysterotomy closure has begun, decrease the volatile agent to 0.5 MAC. Dose the epidural with 0.25% bupivacaine + 3-4 mg preservative-free morphine for postoperative pain control. If neuraxial anesthesia is contraindicated, then an opioid intravenous PCA may be used for postoperative pain control. Following the completion of the patient's skin closure, turn off the volatile agent and proceed with emergence. Bedrest is indicated following fetal surgical interventions and a cesarean delivery is required because of the "classic" location of the uterine incision.

Special circumstances:

  • Early or mid-gestational fetal surgeries: Start tocolysis preoperatively. Indomethacin may be given orally during preoperative evaluation, or given rectally immediately following induction of anesthesia. Magnesium sulfate is added with an IV loading dose of 6 gm followed by an infusion of 2-3 g every hour. The primary goal is to prevent development of uterine contractions following the completion of the surgical intervention and the replacement of the fetus. Magnesium is the first line tocolytic utilized, but in order for this to be effective it needs to be started earlier in the case.

  • Detailed orchestration of events between the surgeon and the anesthesiologist is required. Desflurane is the volatile agent of choice for uterine relaxation due to its insolubility and the speed with which it can be eliminated. The uterine relaxation which is required to complete the EXIT procedure needs to be rapidly reversible to prevent uterine atony following the completion of the delivery. Tocolysis is not indicated, and in fact it is contraindicated. Decrease the MAC level of agent and/or convert to intravenous anesthetic agents before cutting the umbilical cord. This allows uterine contractility to return before the placenta is delivered and the potential for severe uterine atony occurs.

Regional anesthesia

Used for postoperative pain control rather than surgical anesthesia.

Neuraxial

Benefits: Excellent pain coverage; may be safer than general anesthesia in a pregnant patient.

Drawbacks: Unable to provide uterine relaxation required to complete fetal surgery.

Peripheral nerve block

Benefits: TAP blocks can be used for postoperative pain control if there are contraindications for neuraxial analgesia. The anesthesiologist would need specific knowledge and experience in providing TAP blocks. May not provide as complete pain relief as a functioning epidural.

Drawbacks: Knowledge and experience of TAP blocks is required. There may be increased risk for local anesthetic toxicity if multiple regional blocks are placed.

General anesthesia

Benefits: 2.0 MAC volatile agent will provide sufficient uterine relaxation to allow access to the fetus and prevent preterm labor.

Drawbacks: Increased risk for pulmonary and/or cardiovascular compromise while conducting a general anesthetic in a pregnant individual.

Other issues: Possible malignant hyperthermia concerns. Increased nausea and vomiting is associated with volatile agent anesthesia.

Airway concerns: Pregnant patients pose a higher potential for difficult airway management due to tissue redundancy, edema, increased abdominal and breast size. They also have increased aspiration risks.

Monitored anesthesia care

Benefits: None

Drawbacks: Not able to provide sufficient maternal anesthesia or adequate uterine relaxation to complete the procedure.

Other Issues: Increased risk for maternal movement.

6. What is the author's preferred method of anesthesia technique and why?

What prophylactic antibiotics should be administered?

Consult the obstetrician and pediatric surgeon. There are no Surgical Care Improvement Project (SCIP) recommendations for these procedures; 1-2 g cefazolin is commonly used.

What do I need to know about the surgical technique to optimize my anesthetic care?

  • Using a combination of general and neuraxial anesthesia appears to provide the best results.

  • Discuss in detail the different phases of the procedure with all of the participants in advance to avoid confusion during the case.

What can I do intraoperatively to assist the surgeon and optimize patient care?

Close monitoring and tight hemodynamic management of the mother plus uterine relaxation will provide the surgeons the best possible environment.

What are the most common intraoperative complications and how can they be avoided/treated?

High doses of volatile agents depress maternal cardiac output and, in the extreme, maternal hemodynamic collapse. Provide vigilant care and careful monitoring with early and aggressive treatment of hypotension. Should hemodynamic collapse occur, act swiftly with pressors, inotropes and chest compressions when indicated. Recent studies suggest phenylephrine is the vasopressor of choice to maintain maternal mean arterial pressure based on evidence that ephedrine crosses the placenta and causes fetal hypermetabolism and tachycardia. Treat maternal hemorrhage aggressively. The goal is to maintain adequate cardiac output and maintain oxygen carrying capacity. Have type and cross-matched blood available in the operating room (OR) and consider transfusion before fetal distress develops. Fetal blood loss can occur. Prior to starting the procedure, calculate a maximum allowable blood loss based on estimated fetal weight and minimal allowable hemocrit (HCT). Be ready to transfuse if you are concerned that the fetal blood loss has reached this point.

Complications

Cardiac: Maternal cardiovascular compromise poses a grave threat to both patients during fetal surgery. A unique concern here is supine hypotensive syndrome or inferior venocaval compression syndrome where the gravid uterus can compress the inferior vena cava and impede venous blood return from the lower extremities to the heart. Signs and symptoms are maternal hypotension, nausea and dizziness if awake, and fetal bradycardia. Always place the gravid patient in a position of slight left uterine displacement after 20-24 weeks gestation. Another concern is the development of either an air or amniotic fluid embolism. Air embolism signs and symptoms include sudden cardiovascular instability, due to loss of preload. This is followed by loss of the end tidal CO2 tracing once the air embolism reaches the pulmonary circulation. If it reaches the left side of the heart through a patent foramen ovale, the embolism can reach the brain causing a stroke or the heart via the coronary arteries producing myocardial ischemia or infarction.

Pulmonary: Due to an overall dilution of the plasma protein concentration leading to decreased plasma oncotic pressure, parturients have an increased risk for pulmonary edema. Tocolytic therapy may also be associated with pulmonary edema. Close monitoring of the parturient's fluid status is imperative, and central venous catheterization may be indicated in some cases. If severe blood loss occurs that requires large volumes of maternal fluid replacement, consider leaving the parturient intubated to allow for diuresis and increased oxygen requirement. Fetal compromise can occur due to pulmonary edema-induced maternal hypoxia.

Neurologic: While neuraxial analgesia is indicated postoperative pain management, even mild hypotension in a gravid patient may lead to development of nausea and emesis. The cause is hypoperfusion of the brain stem, thus the immediate therapy of choice is not an antiemetic but ephedrine or phenylephrine depending on maternal heart rate, followed by a moderate fluid bolus. Once the hypotension is resolved, consider administration of an antiemetic.

a. Neurologic:

N/A

b. If the patient is intubated, are there any special criteria for extubation?

  • Ensure analgesia and adequate tocolysis in early to midgestation fetal surgical interventions.

  • Ensure adequate uterine tone before considering emergence and extubation following EXIT procedure.

  • Ensure optimal fluid management. To assess pulmonary function prior to extubation, check breath sounds bilaterally for signs of pulmonary edema, ensure adequate urine production and if significant bleeding did occur, consider obtaining an arterial blood gas sample while the patient remains intubated and spontaneously ventilating. If any concern for pulmonary insufficiency exists, do not extubate. Treat moderate to severe pulmonary edema with intubation, ventilation, and diuresis.

c. Postoperative management

What analgesic modalities can I implement?

Epidural analgesia is optimal. Preservative-free morphine 4 mg may be used. Another option is to infuse a low dose local anesthetic such as 0.1% bupivacaine plus opioid by continuous or patient-controlled epidural infusion. Patient controlled intravenous analgesia is another possibility.

What level bed acuity is appropriate?

Due to the complexity of these patients and their procedures, a high acuity Labour and Delivery (L&D) bed or an intensive care unit (ICU) admission for at least 24 hours is appropriate. In addition to monitoring the fetus, you must also monitor for uterine contractions to optimize tocolysis if the intervention did not include delivery. To streamline patient care, it is optimal to create and train a small care team to provide the post operative care for all of these patients, thus improving consistency.

What are common postoperative complications, and ways to prevent and treat them?

For the mother, Deep vein thrombosis (DVT) prophylaxis must occur with stockings and pharmacologic therapy soon after surgery due to the required bed rest for the remainder of her pregnancy. Other concerns include preterm labor, uterine or fetal bleeding, wound infection, and postoperative pulmonary edema. Maternal supine hypotension syndrome remains a concern. Providing adequate post operative pain control may produce pulmonary or cardiovascular issues that require close attention. Fetal post operative care involves the prevention of premature labor. Every other day fetal cardiac ultrasounds are needed to ensure no ductal constriction has developed from indomethacin therapy. Fetal heart tone monitoring is also essential.

What's the Evidence?

Bouchard, S, Johnson, MP, Flake, AW, Howell, LJ, Myers, LB, Adzick, NS, Cromblehome, TM. "The EXIT procedure: experience and outcome in 31 cases". J Pediatr Surg. vol. 37. 2002. pp. 418-26.

(The article provides a detailed description of an anesthetic for the EXIT procedure. The doses for oxytocin infusions, methergine and prostaglandins were obtained from this source.)

Cote, CJ, Lerman, J, Tordes, ID. A practice of anesthesia for Infants and Children. Saunders/Elsevier. 2009.

(See the "Anesthesia for Fetal Surgery" chapter.)

DeBuck, F, Deprest, J, Van de Velde, M. "Anesthesia for fetal surgery". Curr Opin Anesthesiol. vol. 21. 2008. pp. 293-7.

(This paper describes the recent growth in the utilization of the EXIT procedure in addition to describing the use of nitroglycerin as an alternative to elevated levels of volatile agents for uterine relaxation. The use of a nitroglycerin infusion was combined with local and regional anesthetic techniques to allow for a volatile agent-free anesthetic option.)

Adzick, NS, Thom, EA, Spong, CY. "A randomized trial of prenatal versus postnatal repair of myelomeningocele". N Engl J Med. vol. 364. 2011. pp. 993-1004.

(This study compared intrauterine surgery with conventional management and found that prenatal surgery reduced the need for VP shunting andimproved motor outcomes, but was associated with both maternal and fetal risks.)

Garcia, P, Olutoye, O, Ivey, R, Olutoye, O. "Section Editor: Riou B. Case Scenario: Anesthesia for maternal-fetal surgery. The ex utero intrapartum therapy procedure (EXIT)". Anesthesiology. vol. 114. 2011. pp. 1446-52.

(Garcia et al provide an review of the anesthetic requirements for completing an EXIT procedure. Of note, this was one source that directly reported the potential danger of polyhydramnios and fetal surgery. This article also provided reference to the recently developed belief that ephedrine has actually been described to cross the placenta and cause subsequent fetal instability, thus promoting phenylephrine as the vasopressor of choice to maintain maternal mean arterial pressure within 20% of preanesthetic baseline.)

Golombeck, K, Ball, RH, Lee, H, Farrell, JA, Farmer, DL, Jacobs, VR, Rosen, MA, Filly, RA, Harrison, MR. "Maternal morbidity after maternal fetal surgery". Am J Obstet Gynecol. vol. 194. 2006. pp. 834-9.

(This paper depicts/describes the type and frequecy of maternal complications reported by thier records for the different types of fetal surgeries.)

Wu, D, Ball, RH. "The maternal side of maternal-fetal surgery". Clin Perinatol. vol. 36. 2009. pp. 247-53.

(This paper describes in detail the concept of the elevated maternal risk associated with fetal surgery without direct gain, thus completing the procedure based on the altruistic gains of the fetus.)

Boat, A, Mahmoud, M, Michelfelder, EC, Lin, E, Ngamprasertwong, P, Schnell, B, Kurth, CD, Crombleholme, TM, Sadhasivam, S. "Supplementing desflurane with intravenous anesthesia reduces fetal cardiac dysfunction during open fetal surgery". Paediatr Anaesth. vol. 20. 2010. pp. 748-56.

(This study found that supplementing desflurane with intravenous anesthesia decreased use of desflurane and better preserved fetal cardiac function.)

Chescheir, NC. "Maternal-fetal surgery: where are we and how did we get here?". Obstet Gynecol. vol. 113. 2009. pp. 717-31.

(This review discusses "where are we and how did we get here" for congenital diaphragmatic hernias, open spina bifida, and twin-to-twin transfusion.)

Hartnick, CJ, Barth, WH, Cote, CJ, Albrecht, MA, Grant, PE, Geyer, JT. "A pregnant woman with a large mass in the fetal oral cavity". N Engl J Med. vol. 360. 2009. pp. 913-21.

(This case report describes EXIT therapy for a large cystic mass in the fetus' mouth arising from the ventral surgace of the tongue.)
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