Anesthesiology

Omphalocele

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What the Anesthesiologist Should Know before the Operative Procedure

Omphalocele and gastroschisis are significant abdominal wall defects with a combined incidence of 1:2000 to 1:4000 live births. Omphalocele is the herniation of abdominal contents in the midline, composed primarily of midgut. The herniated gut often occurs with associated herniation of the liver, in a hernia sac protruding through the midline defect. Gastroschisis is herniation of the bowel lateral to the umbilicus, without other viscera in the herniation.(Figure 1, Figure 2).

Figure 1.

Omphalocele: note the midline position and hernia sac covering the herniated viscera (courtesy S. Smith)

Figure 2.

Gastroschisis: note the herniation is lateral to the umbilicus, involves only bowel and does not have a sac (Courtesy S. Smith).

Abdominal wall defects result from inadequate mesodermal development which results in enlargement of the diameter of the umbilical ring. The amnion remains attached to the margins of the body wall and produces a persistent communication between the body cavity and the extraembryonic celom. In babies with omphalocele, failure of central fusion at the umbilical ring causes incomplete closure of the abdominal wall and persistent herniation of the midgut. The abdominal viscera are contained in a translucent sac, which is composed of amnion, Wharton jelly, and peritoneum. In about 50% of cases, the liver, spleen, and ovaries or testes also are found in the hernia sac along with the bowel.

The differences between gastroschisis and omphalocele are summarized in Table 1.

Table 1.

Differentiating Characteristics Between Gastroschisis and Omphalocele
Characteristic Omphalocele Gastroschisis
Herniated viscera Bowel ± liver Bowel only
Sac Present Absent
Associated anomalies Common (50%) Uncommon (<10%)
Location of defect Umbilicus Right of umbilicus
Mode of delivery Vaginal/caesarean Vaginal
Incidence of prematurity birth 6% 28%
Surgical management Nonurgent Urgent
Prognostic factors Associated anomalies Condition of bowel

1. What is the urgency of the surgery?

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

Because the exposed abdominal viscera could be damaged and the likelihood of systemic infection and sepsis rapidly increases after delivery, an infant with omphalocele requires immediate attention in the delivery room and subsequent care in the neonatal intensive care unit.

Omphalocele is not a surgical emergency. However, the neonate does require special care in order to avoid trauma and ischemia of the hernia contents, and to prevent hypothermia and hypoglycemia. The herniated midgut and abdominal content may suffer significant trauma; the hernia sac must be treated with care to avoid rupture and the contents handled gently to reduce chance of trauma. If the sac is ruptured and the viscera are exposed, the infant is at risk for systemic infection and septic shock. Timely evaluation for the presence of other associated defects is important to avoid further complications and to devise a proper plan of care.

2. Preoperative evaluation

Nearly half of all infants with omphalocele have other anomalies whereas associated anomalies are rare with Gastroschisis.

Infants with omphalocele also may have malrotation of the gut, cardiovascular anomalies (18-24%), chromosomal abnormalities (48%) including trisomy 13 and trisomy 18, vesico-intestinal fissure or bladder exstrophy (11.9%), and Beckwith-Wiedemann(6.5%).

The cardiovascular anomalies may be significant and life-threatening. Intracardiac lesions range from ventricular septal defects (VSD) to the more serious pentalogy of Cantrell (a variant of the tetralogy of Fallot - TOF). The components of the pentalogy of Cantrell are epigastric omphalocele, cleft sternum, anterior diaphragmatic hernia (hernia of Morgagni), absent pericardium, and cardiac defects.

In babies with Beckwith-Wiedemann syndrome (i.e., exomphalos, macroglossia, and gigantism) multiple systems are affected. These patients have coarse, rounded facial features; hyperplasia of the pancreatic islet cells and associated hypoglycemia; visceromegaly; and genitourinary abnormalities. Later in life these patients face additional problems including a higher incidence of Wilms tumor, hepatoblastoma and adrenocortical neoplasms. The enlarged tongue may make mask ventilation and tracheal intubation quite difficult.Other associated abnormalities include creases in ear lobes, enlargement of some organs and tissues, external ear (pinna) abnormalities and low-set ears, large size for gestational age; large, prominent eyes, mild microcephaly, diastasis recti, seizures and cryptorchidism..

a. If an intracardiac defect is suspected on screening echocardiography, the infant requires a more thorough cardiac examination by a pediatric cardiologist to avoid perioperative complications or death. Infants suspected of having Beckwith-Wiedemann syndrome should be evaluated for hypoglycemia and electrolyte disturbances, which should be corrected prior to surgery.

b. A chest radiograph should be performed to estimate thoracic and lung volume, because these infants are at risk of restrictive lung disease and often need postoperative ventilatory support.

c. Primary surgical correction may need to be delayed in order to better assess any concomitant diseases. Placement of a silo at the bedside in the NICU or in the operating room to cover the defect will protect the abdominal contents, and allow time for further clinical evaluation, as needed.

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

Congenital conditions that may coexist with omphalocele are discussed above. Some of these conditions may be life threatening if not treated appropriately and in a timely manner.

Patients with cardiovascular anomalies may need several surgical procedures to correct the underlying defects. Endocrine problems such as hypocalcemia require lifelong close monitoring and treatment. Infants with Beckwith-Wiedemann syndrome will need close follow up for a variety of conditions, including: ongoing endocrine disease (hypoglycemia, hypocalcemia); surgical correction of bladder exstrophy, if present; airway support if the airway is compromised because of a large tongue. Later in life patients may need treatment for inguinal hernias, bowel obstruction caused by adhesions, or for treatment of neoplasms (Wilms or hepatoblastoma).

b. Cardiovascular system

Infants with simple VSD may require VSD correction. Infants with complex cardiovascular pathology like pentalogy of Cantrell require proper acute surgical management and lifelong follow-up.

c. Pulmonary

Infants with omphalocele may have a small thoracic cavity and associated pulmonary hypoplasia. This restrictive lung disease may be severe enough to require the patient to be on mechanical ventilation for a prolonged period after birth.

d. Renal-GI:

Children with Beckwith-Wiedemann syndrome may have anomalies of the renal system including structural abnormalities, nephromegaly, or nephrocalcinosis. Usually these do not cause problems in the immediate neonatal period, the time of the initial treatment of omphalocele.

e. Neurologic:

Children with Beckwith-Wiedemann syndrome may have substantially delayed development as the child grows.

f. Endocrine:

Patients with omphalocele and Beckwith-Wiedemann syndrome have macrosomia and may be suffer from profound hypoglycemia. The anesthesiologist should monitor the infant's glucose closely and treat if hypoglycemia is detected.

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)

N/A

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?

N/A

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

N/A

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

N/A

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.

Infants with omphalocele are not at especially increased risk to develop latex allergies. However, as a general practice in pediatric anesthesia and surgery, latex-safe and latex-free environments are recommended; pediatric patients with congenital conditions may require multiple procedures and will be exposed repeatedly to latex.

l. Does the patient have any antibiotic allergies- [Tier 2- Common antibiotic allergies and alternative antibiotics]

N/A

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

N/A

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

Laboratory tests should include hematocrit/hemoglobin and blood glucose. The anesthesiologist should be aware and be prepared to treat polycythemia or anemia, or hypoglycemia if present.Expected normal values for hematocrit, hemoglobin, glucose or other laboratory tests are those expected in any neonate, and vary with the degree of prematurity and post-natal age of the patient.

See normal laboratory values according to postnatal age. Also, measure hemoglobin levels and blood glucose values.

Patients with omphalocele should have an echocardiogram to evaluate the heart and great vessels. An electrocardiogram is helpful in evaluating the degree of ventricular strain or hypertrophy. As some infants may have pulmonary hypoplasia, a chest radiograph will aid in assessing the size of the thoracic cavity and also lung volumes. Serum or blood glucose should be checked regularly to detect hypoglycemia.

Abdominal ultrasound may point to the presence of undescended testes.

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

Initial management of the infant with omphalocele is supportive in the neonatal intensive care unit. If the hernia sac is ruptured or leaking, a Silastic silo may be placed to cover the herniated viscera.

Surgical repair of the abdominal wall defect is performed under general endotracheal anesthesia. The patient should have standard monitors, including monitoring of ECG, noninvasive blood pressure, temperature, and pulse oximetry. In addition, an arterial line may be helpful to closely monitor blood pressure and obtain blood samples for glucose, hemoglobin, and other laboratory tests. A central line is usually placed either by the anesthesiologist or the surgeon for intraoperative care and postoperative total parenteral nutrition [TPN] support. The premature infant or the child with pulmonary hypoplasia and/or small thoracic cage likely will need extended mechanical ventilatory support postoperatively.

a. Regional anesthesia

In experienced hands, an epidural catheter may be placed via the thoracic or high lumbar approach to provide intraoperative and postoperative analgesia. Adequate regional analgesia can reduce the amount of time the infant needs mechanical ventilation. Placement of the epidural catheter should be done by a pediatric anesthesiologist experienced in the technique.

b. General Anesthesia

The general anesthetic technique commonly used is a balanced technique with fentanyl, neuromuscular blockade, and low-dose volatile anesthetic like sevoflurane. Remifentanil infusion is an excellent alternative to fentanyl. The pharmacology of remifentanil has significant benefit for the neonate; the drug has a rapid onset, is easily titrated to achieve the depth of analgesia required for intraoperative care and has a rapid offset, allowing for more rapid extubation. For infants with a relatively small defect that is easily closed, it may be possible to extubate the patient soon after surgery.

If a regional anesthetic technique is not used and the child requires significant doses of opioid, the patient may need postoperative ventilatory support for several days.

c. Monitored Anesthesia CareN/A

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

Prophylactic antibiotics should be used. For neonatal surgery these often include ampicillin and gentamicin to prevent neonatal sepsis. Alternately, a broad spectrum antibiotic like ampicillin-sulbactam (Unasyn) may be preferred by the surgeon.

The primary challenges for the anesthesiologist include those seen with any neonatal surgery—adequate mechanical ventilation with the lowest PIP required; adequate supplemental oxygen sufficent to maintain SpO2 above 93%-95% as too much oxygen may result in pulmonary and retinal damage. Airway management in infants with Beckwith-Wiedemann syndrome may be difficult because of the presence of a large tongue.

The primary goal of surgical treatment is to replace the gut back in the abdomen. However, the abdominal cavity may be too small to accomodate all of the content and closure of the abdominal wall over the bowel may result in an abdominal compartment syndrome and a significant reduction in the lung volumes, particularly FRC. This can result in the need for higher pressures to achieve adequate ventilation. In some case, venous return to the heart may be compromised, resulting in hypotension. Therefore, staged reduction may be better.

a. Neurologic:

N/A

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

Infants with omphalocele will need general endotracheal anesthesia for surgery. The child may be extubated soon after surgery if the abdominal cavity easily accommodates the extra-abdominal contents. In some cases where primary closure is possible but the ventilation may be compromised because of the abdominal contents pushing rostrally and impeding proper chest expansion. In these circumstances, the infant should be kept intubated and mechanical support continued. Several days may be required for postoperative edema of the bowel to subside and for the infant to be able to sustain adequate spontaneous ventilation. In this instance, the patient also will need prolonged total parenteral nutrition until bowel function is adequate to accommodate gut feeds.

c. Postoperative management

Postoperatively, the child should be extubated to spontaneous ventilation as soon as it is safe.

Infants who have adequate thoracic capacity and in whom the herniated contents can be readily replaced in the abdomen may be able to breathe on their own and may tolerate extubation to spontaneous ventilation.

Many infants will require mechanical ventilation for several days after surgery.

These patients may require significant pain management for several days after surgery. Intravenous opioids using infusions (for example, 1-2 mcg/kg/h of fentanyl) are effective for the initial few days. Intermittent dosing of opioids in combination with acetaminophen may be sufficient afterward. Alternately, the infant may benefit from epidural analgesia provided via a thoracic, high-lumbar or caudal catheter which has been threaded rostrally. Placement and management of regional anesthesia in neonates and infants should be performed only by experienced pediatric anesthesiologists. Care of the epidural catheter and nursing care of these infants also requires a nursing team with sufficient knowledge and experience.

Infants receiving opioids or epidural analgesia should be closely monitored for respiratory depression.

What's the Evidence?

Baird, PA, MacDonald, EC. "An epidemiologic study of congenital malformations of the anterior abdominal wall in more than half a million consecutive live births". Am J Hum Genet. vol. 33. 1981. pp. 470-8.

(Excellent large study providing a good overview.)

Stoll, C, Alembik, Y, Dott, B, Roth, M-P. "Omphalocele and gastroschisis and associated malformations". Am J Med Genet. vol. 146A. 2008. pp. 1280-5.

Wilson, RD, Johnson, MP. "Congenital abdominal wall defects: an update". Fetal Diagn Ther. vol. 19. 2004. pp. 385-98.

(Update on the syndrome with an excellent discussion of embryology and prenatal aspects of care.)

Brantberg, A, Blaas, H-G K, Haugen, SE, Eik-Nes, SH. "Characteristics and outcome of 90 cases of fetal omphalocele". Ultrasound Obstet Gynecol. vol. 26. 2005. pp. 527-37.

(Excellent discussion on omphalocele diagnosed in utero and the issues/conditions imapcting outcome. The anesthesiologist and the perinatal team should be aware of the risks associated with different variants of fetal omphalocele.)

"Anesthesia in Beckwith-Wiedemann syndrome". Pediatr Anesth. vol. 14. 2004. pp. 778-80.

Bosenberg, A. "Anaesthesia and pentalogy of Cantrell". South Afri J Anaesth Analg. 2004.

(Brief useful discussion on the clinical challenges facing the anesthesiologist caring for a child with pentalogy of Cantrell.Good brief discussion on issue that the anesthesiologist may face in caring for an infant with Beckwith-Wiedemann syndrome.)

Ross, AK, Davis, PJ, Dear, G de L, Ginsberg, B, McGowan, FX, Stiller, RD, Henson, LG, Huffman, C, Muir, KT. "Pharmacokinetics of remifentanil in anesthetized pediatric patients undergoing elective surgery or diagnostic procedures". Anesth Analg. vol. 93. 2001. pp. 1393-1401.

(Very good article on the use of remifentanil in the neonate and pediatric age group.)

Davis, PJ, Cladis, FP. "The use of ultra-short-acting opioids in paediatric anaesthesia". Clin Pharmacokinet. vol. 44. 2005. pp. 787-96.

Brett, C, Davis, PJ, Davis, PJ, Cladis, FP, Motoyama, EK. "Anesthesia for general surgery in the neonate". Anesthesia for Infants and Children. Elsevier Mosby. 2011. pp. 554-604.

(Review and good overview on the benefits and precautions involved with the perioperative use of ultra-short acting opioids including remifentanil.)
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