Pectus Excavatum

Pectus excavatum is one of the most common congenital anomalies in the United States. It is the most common chest wall deformity in children, with an incidence of approximately 1:1000. There is a male predominance, with an incidence of 1:400 in male children. In pectus excavatum, the lower sternum is commonly depressed posteriorly relative to the upper sternum and costal cartilages, creating a concave chest wall deformity. The etiology is unknown, but hypotheses include an intrinsic abnormality of the costal cartilage or overgrowth of the cartilages. ^,

Although usually present at birth, pectus excavatum is often diagnosed in early childhood or adolescence. There has been a misconception that pectus excavatum is solely a cosmetic defect, which can delay correction of this condition until adulthood. Clinically, patients can have a variety of symptoms that typically worsen with age. The most common symptoms are dyspnea with exertion and loss of endurance, but also include chest pain, palpitations, and dizziness. Associated conditions include mitral valve prolapse, cardiac dysrhythmias, and connective tissue disorders. ^,

Evaluation

The workup for pectus excavatum typically includes a computed tomography (CT) scan of the chest and may include echocardiography and pulmonary function tests (PFTs). The severity of symptoms often does not correlate with the severity of the chest wall deformity.

The Haller Index, a measure typically calculated on a CT scan, is the most commonly used objective measure of the degree of the defect in pectus excavatum. To calculate this metric, the widest transverse diameter of the inner chest is divided by the distance between the posterior sternum and anterior spine. ^, A Haller Index of greater than 3.25 is generally thought to be an indicator of moderate to severe deformity and is an indication for surgery. Of note, this number was initially determined by comparing a small group of patients with pectus excavatum who underwent repair with healthy controls, and was not subsequently validated with further studies. The accuracy of the Haller Index can be limited with variations in thoracic shape, particularly with wide or narrow chests, and asymmetry. A retrospective review in a series of patients who underwent repairs did not show a correlation between the Haller Index and operative time, postoperative bar infection, or length of hospitalization. Nonetheless, at this time, this index is still the most commonly used index to quantify the severity of pectus excavatum.

Because the depressed portion of the sternum can result in compression of the anterior structures of the heart, namely the right atrium and right ventricle, an echocardiogram is useful for evaluation of cardiac anatomy and function. Other features on echocardiogram to note include mitral valve prolapse, and if present, should include evaluation of the aortic root and valve in patients thought to have connective tissue disease. An electrocardiogram (ECG) can identify any cardiac dysrhythmias that may result from this chest wall deformity.

Static and exercise PFTs can be used to characterize the effect on lung mechanics. PFTs may show features of both restrictive disease and mild obstructive disease. Less commonly, cardiopulmonary exercise testing can be used to further assess the physiologic changes that are a result of the pectus excavatum and may suggest whether surgical repair could be beneficial.

Surgical Approach

Indications for surgery can be found in Box 1 . ^, Generally, modifications of 1 of 2 surgical approaches are used in the repair of pectus excavatum: the open approach described by Ravitch in 1949, and the minimally invasive approach first described by Nuss in 1998. In the open Ravitch procedure, deformed cartilage is resected, and a metal strut can be placed to support the sternum. This strut is left in place for 6 months to 1 year before it is removed. In contrast, in the minimally invasive Nuss procedure, 1 or 2 substernal concave bars are placed transthoracically posterior to the sternum, then rotated into a convex position, displacing the sternum outward. This bar is left in place for approximately 2 years, allowing the sternum and chest wall to remodel, and then removed. Thoracoscopy can also be used for better visualization of the heart and surrounding structures, to decrease the risk of cardiac injury during the insertion of the substernal bars. ^,

Over the past few decades, the Nuss procedure has become the standard approach in many centers because of its minimally invasive approach, with short operating time and good long-term cosmetic results. ^, However, disadvantages include longer hospitalization, severe postoperative pain, and the risk of hemorrhage due to cardiac or vascular injury as a result of the blind approach. ^,

Anesthetic Considerations

Postoperative

Pectus excavatum repair is one of the most painful surgeries performed in the pediatric population. As such, postoperative pain management has been a point of extensive research over the past several years, and studies have shown that multimodal analgesia is the most effective. Although there is no unified consensus on the best approach at this time, there are many techniques that can be used for effective postoperative analgesia aside from opioids, including regional techniques and nonopioid adjuncts. A thoracic epidural, placed at T5-T6 or T6-T7, is often used for pain control intraoperatively and postoperatively, but alternatives include bilateral paravertebral catheters or erector spinae plane blocks or catheters, which have a lower risk of hypotension but require more expertise. ^, Surgical interventions for pain control include intraoperative catheter placement into either the subpleural or subcutaneous space, and cryoablation of intercostal nerves at the level of the incision and 1 or 2 levels above and below the incision ( Fig. 1 ). In the perioperative period, the preceding measures are often supplemented with other adjuncts, including a patient-controlled anesthesia (PCA) or intermittent opioids, acetaminophen (Tylenol), diazepam (Valium), methocarbamol, ketorolac (Toradol), ketamine, methadone, dexamethasone, and clonidine. ^,

Cryoablation of intercostal nerves during the Nuss procedure. This photograph shows the view via thoracoscopy after cryoablation of the intercostal nerves, as a regional technique for perioperative pain management.

Key Points

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  Preoperative evaluation should include a detailed assessment of the patient’s cardiopulmonary function, including the chest CT scan, ECG, and, if available, echocardiogram and PFTs.

  
  
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  Although the procedure typically has minimal blood loss, there is a potential for massive blood loss due to the proximity to the heart and major vessels. As such, the patient should have an active type and screen, adequate IV access, and, if indicated, arterial line.

  
  
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  Serious complications of the Nuss procedure include injury to the heart and cardiac arrhythmias. If a patient has had prior cardiac surgery, a cardiac surgeon, cardiac bypass circuit, and perfusionist should be available, because of the elevated risk of cardiac injury during this procedure.

  
  
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  As the Nuss bar is advanced through the mediastinum, arrhythmias such as frequent premature atrial and ventricular contractions, bradycardia, or even asystole can occur due to irritation of the heart and surrounding structures.

  
  
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  Although the Nuss procedure is minimally invasive, it is a very painful procedure, and multimodal analgesia should be used for postoperative pain management. This can include a combination of regional anesthesia (epidural, paravertebral, or erector spinae catheters), cryoablation, and other adjuncts like acetaminophen, diazepam, methocarbamol, ketorolac, ketamine, methadone, dexamethasone, and clonidine.

Thoracic Insufficiency Syndrome

Thoracic insufficiency syndrome encompasses congenital or acquired chest wall defects, spinal deformities, neuromuscular dysfunction, or other anatomic disorders of the thorax that can lead to restrictive lung disease. ^, Conditions that can lead to thoracic insufficiency syndrome include Jeune syndrome, Jarcho-Levin syndrome, connective tissue disorders, spina bifida, spinal muscular atrophy, scoliosis, and many others. Children diagnosed with these syndromes can be extremely debilitated with chronic contractures and restrictive lung disease. ^,

The diagnosis of this syndrome relies on symptoms, signs, and radiography. ^, Symptoms include limited exercise tolerance, recurrent lower respiratory tract infections, and pulmonary hypertension, and signs can include tachypnea at rest, nocturnal hypercarbia and hypoxemia. In early-onset scoliosis, the natural history of the disease leads to decreased life expectancy, with increased mortality rates of 2 times normal by age 40 and 3 times normal by age 60, largely due to respiratory failure or cardiovascular disease. Early diagnosis and treatment is important in preventing or mitigating progression to significant thoracic insufficiency.

Evaluation

Although there is no standardized protocol for evaluating children with thoracic insufficiency syndrome, various imaging studies can provide an estimate of severity and can also be used for serial assessments of lung volume or pulmonary function. ^, Anteroposterior and lateral radiographs of the spine are used to measure the height of the thoracic spine and the Cobb angle, which is the maximal angle between the superior and inferior endplates of the terminal vertebrae of the spinal curvature. ^, The Cobb angle is often measured serially to assess for changes over time. CT scans of the chest and lumbar spine can give a more accurate assessment of lung volume, particularly in children younger than 3 years if PFTs cannot be obtained. Other studies that can be useful include ventilation-perfusion scans to assess for and quantify relative ventilation and perfusion in the right versus left lung, echocardiograms if there is a suspicion for early cor pulmonale, and MRI of the spine to assess for any spinal cord abnormalities.

Surgical Approach

When limitation of respiratory function or normal lung growth due to thoracic insufficiency syndrome is progressive, surgical treatment can be pursued. VEPTR can also be used for congenital scoliosis that does not respond to bracing. ^, Historically, early-onset scoliosis was treated with early spine fusion with immobilization, but many of these patients had poor pulmonary function, with loss of thoracic height from the spine fusion and decreased lung volumes. As such, in younger children, this approach has largely been replaced by the use of various devices, including the growing rods, VEPTR, MAGnetic expansion control (MAGEC) rods, and bracing.

Although studies are still being conducted to evaluate the efficacy of these newer growth-sparing interventions, evidence suggests that VEPTR insertion may improve respiratory function, allowing for the weaning of respiratory support in patients requiring mechanical ventilation or preventing the need for respiratory support in patients not currently requiring ventilation or supplemental oxygenation, and decrease mortality.

Vertical Expandable Prosthetic Titanium Rib

The VEPTR was approved by the Food and Drug Administration (FDA) in 2004 as a humanitarian use device to treat children with thoracic insufficiency syndrome. ^, The VEPTR device is a construct that attaches to the ribs and, once placed, can be progressively expanded, allowing for continued growth of the spine while stabilizing it. These are typically anchored to another rib, the spine, or pelvis. The particular surgical approach using these devices is guided by the type of volume depletion deformity (VDD). ^,

In VDD Type I, characterized by absent ribs and early-onset scoliosis, the approach is a thoracotomy on the side without ribs, intraoperative correction of scoliosis by distraction, then stabilization using VEPTR devices. ^, In VDD Type II (the most common type), which is characterized by fused ribs and early-onset scoliosis, the surgical approach involves creating an opening wedge thoracostomy (thoracotomy on the side with fused ribs, followed by transverse rib osteotomy and distraction of the edges of the ribs), and stabilization of the expanded thorax using VEPTR devices. ^{, ,} In VDD Type IIIa, characterized by a short thorax (eg, Jarcho-Levin syndrome), a staged bilateral procedure is performed, using opening wedge thoracostomies and insertion of rib-to-rib VEPTR. In VDD Type IIIb, characterized by a narrow thorax (eg, Jeune syndrome, infantile scoliosis with windswept deformity), staged bilateral dynamic segmental expansion thoracoplasties are performed, with rib osteotomies to mobilize the chest wall and insertion of a curved VEPTR to stabilize the chest wall. ^,

MAGnetic Expansion Control Rods

The MAGEC rods, approved by the FDA in 2014, use a magnetic expansion mechanism that can be activated by an external set of magnets. As a result, the MAGEC rods do not require multiple expansion surgeries and can be lengthened more frequently without the need for general anesthesia.

Anesthetic Considerations

Key Points

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  Preoperative evaluation of thoracic insufficiency syndrome should include a review of the available imaging studies, including radiographs, CT scans, PFTs, and echocardiograms, as well as a thorough assessment of underlying comorbidities.

  
  
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  If the patient has an acute upper or lower respiratory infection, surgery should be postponed until the infection is resolved or treated.

  
  
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  The VEPTR and MAGEC rods are new FDA-approved devices that can be used in the treatment of thoracic insufficiency syndrome. Particularly in young patients, these devices provide an alternative to early spine fusion by providing stabilization and continued growth of the spine.

  
  
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  During prone positioning of the patient, it is important to avoid chest wall compression, which can exacerbate difficulty with ventilation and can also lead to acute right to left shunting in children with intracardiac defects.

  
  
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  SSEPs and MEPs should be used for neuromonitoring, and the anesthetic maintenance should be tailored to allow for neuromonitoring and a crisp wake-up test as necessary.

  
  
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  Patients may need mechanical ventilation and ICU admission postoperatively if they were dependent on tracheostomy and mechanical ventilation preoperatively. Pain management will likely involve the use of opioids via continuous infusion, PCA, or NCA, in addition to other analgesic medications.

Craniosynostosis

In normal development, infants have rapid brain growth over the first year of life, pushing apart the cranial sutures, which are growth plates that deposit new bone and allow for expansion of the brain and skull. ^, In craniosynostosis, one or more of the cranial sutures fuse prematurely, causing localized or global growth delay of the skull. ^, Craniosynostosis can be isolated or associated with various syndromes. Most cases of craniosynostosis are nonsyndromic, but the cases of syndromic craniosynostosis can be very complex and challenging to manage. This is because nonsyndromic craniosynostosis usually involves a single suture, whereas syndromic craniosynostosis can involve multiple sutures and other cranial vault bony abnormalities. Associated syndromes include Crouzon syndrome, Apert syndrome, Pfeiffer syndrome, Saethre-Chotzen syndrome, and Muenke syndrome. Children with these syndromes have various clinical features, particularly craniofacial anomalies that can make airway management difficult. Nonsyndromic craniosynostosis is classified by the cranial suture affected: sagittal, metopic, coronal (bilateral or unilateral), or lamboid.

Of note, in children with complex craniosynostosis, approximately 50% may have intracranial hypertension, whereas in simple synostosis, approximately 15% may have intracranial hypertension. ^, Symptoms of elevated intracranial pressure (ICP) can be nonspecific in children and include poor feeding, failure to thrive, headaches, and developmental delay.

Surgical Approach

Historically, in the late 1800s and mid-1900s, suturectomies or strip craniectomies were performed for the treatment of craniosynostosis, but were limited by early refusion at the craniectomy sites. ^, In the 1970s, a new, more invasive technique was introduced that involved the removal of large segments of bone, remodeling of the bone, and stabilization of the bone in a more anatomic position. ^, Although this led to more predictable outcomes, there was significant morbidity due to blood loss, lengthy operations, and prolonged hospitalizations. ^, Traditionally, open cranial vault surgeries for the correction of craniosynostosis are performed from 6 to 12 months of age.

The use of endoscopic techniques for craniosynostosis has been documented in the literature since the 1990s; however, it is often considered to be an innovative procedure, despite its well established safety and efficacy. In endoscopic surgery, the goal is to remove the fused portion of the bone, followed by the use of orthotic therapy (ie, with a helmet) to guide brain and skull growth to recreate normal anatomy. ^, Access requires 1 to 2 small incisions perpendicular to the fused suture, followed by the creation of burr holes over the suture. ^, An endoscope is used for dissection of the dura off of the suture, and a strip of fused bone is removed from the affected suture. ^,

In contrast to open vault surgeries, endoscopic repair of craniosynostosis should be undertaken in infants younger than 6 months, as the procedure relies on brain and skull growth following the procedure for correction. If undertaken in children older than 6 months, there are expandable devices that can be used (springs, distractors) to drive skull growth in a defined direction, but this technique requires a second procedure to remove this device. ^, Research has shown that the endoscopic approach decreases blood loss and transfusion, operative time, length of stay, and perioperative complications including venous air embolism and transfusion-related complications, ^, in addition to improved patient and family experience and cosmetic outcomes.

Anesthetic Considerations

Key Points

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  Craniosynostosis can be associated with a myriad of syndromes, including Crouzon syndrome, Apert syndrome, and Pfeiffer syndrome, that may be characterized by various craniofacial anomalies that can make airway management challenging and may require advanced airway techniques.

  
  
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  Although open repair was typically undertaken between 6 and 12 months of age, endoscopic repair of craniosynostosis is performed at a younger age (<6 months). The procedure is followed by orthotic therapy (ie, helmet) to guide brain and skull growth and recreate normal anatomy. Expandable devices (springs, distractors) can be used to actively drive skull growth in a defined direction if this procedure is undertaken in children >6 months of age.

  
  
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  Compared with open repair, endoscopic repair of craniosynostosis decreases blood loss and transfusion, operative time, length of stay, and perioperative complications including venous air embolism and transfusion-related complications. However, due to the young age and small size of patients undergoing this procedure, it is important to have blood available and transfuse preemptively.

  
  
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  Brisk bleeding and subsequent reduced venous pressures leading to increased risk for venous air embolism can occur quickly due to surrounding large venous sinuses regardless of endoscopic or open repair.

  
  
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  Otherwise healthy patients can typically be extubated in the operating room and be monitored on the neurosurgical floor overnight, before being discharged on postoperative day 1.

Tethered Cord Syndrome

A tethered spinal cord is characterized by the tethering of the lumbosacral spinal cord to inelastic structures caudally, causing a stretching and traction effect on the spinal cord. In tethered cord syndrome (TCS), this tension on the cord can cause symptoms, including back pain, leg pain, motor or sensory deficits in the lower extremities, diminished deep tendon reflexes, bladder dysfunction, incontinence, or scoliosis. Tethered cord is also often associated with other physical signs, including sacral dimples or hair tufts. ^, Of note, although most patients with tethered cord are otherwise healthy, spinal cord abnormalities can often be associated with other anatomic anomalies (eg, VACTERL syndrome), and additional evaluation may be indicated. ^, Evaluation of TCS involves MRI of the spinal cord. Although ultrasound can be used as an initial approach, an MRI is indicated if TCS is suspected.

TCS can be classified into 3 categories. ^, Category 1 TCS includes patients with symptoms that are correlated with the stretch-induced injury to the caudal spinal cord. ^, Causes of category 1 TCS include caudal myelomeningocele (MMC), small lipomyelomeningocele (LMMC), and an inelastic filum terminale. ^, Category 2 TCS includes patients with similar symptoms that may not be fully attributed to the stretch-induced dysfunction, and may be due to injury resulting from local compression and ischemia from dorsal anomalies (eg, MMC, large LMMC). ^, As such, symptoms may be only partially relieved or not relieved at all after detethering of the cord in these patients. ^, Category 3 TCS includes patients with extensive neurologic deficits typically due to damage to the thoracic or high lumbar spinal cord. ^, Category 3 TCS is not true TCS in the sense that the deficits are not correlated with stretch-induced effects on the caudal spinal cord but rather are a result of irreversible neurologic deficits, which in some cases can be due to a lack of functional neurons or replacement of neuronal tissue with fat tissue. ^, This categorization of TCS is useful because surgical release of the tethered cord can only be beneficial in categories 1 and 2. ^,

Although tethered cord release is recommended in patients who are symptomatic, particularly in those with neurologic or urologic deficits, there is no consensus on surgery in the asymptomatic patient with an incidental finding on MRI. Although every operation has its risks, prophylactic surgical intervention may be useful even in asymptomatic patients at risk for TCS, because neurologic and urologic symptoms may not be completely resolved by surgery once they develop. Furthermore, early intervention appears to improve outcomes in patients with TCS.

Surgical Approach

The current standard of care for the management of TCS is open tethered cord release (TCR) via 1-level lumbar laminectomy. ^, Minimally invasive surgery has become increasingly widespread due to shorter operative times and fewer complications. Although most reported minimally invasive TCR procedures to date have been performed in adult patients, there have been reports of minimally invasive approaches for TCR release in children. ^,

The approaches described in these studies were specifically for tight filum terminale, not for more complex causes of TCS (eg, tumors, MMC). ^, As these minimally invasive approaches are still under development, the approaches were all slightly different, involving lumbar hemilaminectomy with endoscopic sectioning of the filum terminale, microscopic tubular approach to laminotomy and sectioning of the filum, and microscopic interlaminar approach that does not involve laminectomy or laminotomy with sectioning of the filum. However, all of these minimally invasive approaches, though with small sample sizes, suggested reductions in postoperative pain, blood loss, and hospital stays. ^{, ,} In particular, there was a suggested likelihood of reduction in retethering with these strategies due to the minimization of injury and inflammation to the subarachnoid space. ^,

Anesthetic Considerations

Key Points

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  Tethered cord can be associated with other congenital anomalies, including anal atresia, cardiac anomalies, tracheoesophageal fistula, renal anomalies, and limb malformations. However, typically patients with tethered cord are otherwise healthy.

  
  
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  Tethered cord can be associated with latex sensitivity, and as such, the gloves and equipment used in the operating room should be latex-free.

  
  
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  Minimally invasive approaches to TCR seem to be associated with reductions in postoperative pain, blood loss, and hospital stays.

  
  
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  Intraoperative monitoring with SSEP, MEP, and intraoperative direct stimulation of the nerve roots is used to monitor neurophysiologic function throughout surgery. As a result, neuromuscular blockade should be avoided after intubation and inhaled anesthetic agents should be minimized or avoided to ensure accurate neuromonitoring.

  
  
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  The most common cause of reoperation after tethered cord release is CSF leak.

Discussion

There have been many advances in pediatric surgery over the past few decades, with some advances using new devices (eg, VEPTR, MAGEC rods) and others using less invasive approaches (eg, Nuss procedure, endoscopic cranial suture release, minimally invasive TCR). Although many of these procedures were initially met with caution or skepticism, continued experience over the past few decades has shown that these procedures are safe and effective.

Clinics Care Points

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