Thoracoscopic Approach to Pediatric Mediastinal Masses


Anterior

Middle

Posterior

Lymphoma

Undifferentiated sarcoma

Neuroblastoma

Germ cell tumor

Lymphoma

Ganglioneuroma

Thymic masses

Foregut duplication cysts

Ganglioneuroblastoma

Undifferentiated sarcoma

Lymphangioma

PNET

Rhabdomyosarcoma

Rhabdomyosarcoma

Lipoma

Lipoma

Hemangioma

Lymphangioma

Hemangioma

Lipoma

Neurofibroma
 
Wilms’ tumor

Hemangioma
  
Rhabdomyosarcoma
  
Foregut duplication cysts





Preoperative Evaluation



History and Physical Exam


Young children cannot articulate their sensations, so parents should be asked to give a detailed history. Particular attention should be paid to symptoms of irritability, pain, fevers, fatigue, shortness of breath, stridor, anorexia, exercise intolerance, nausea, vomiting, and bowel movement changes.

Duplication cysts of the mediastinum often become infected and induce fever and cough. Fever and diarrhea can be symptoms of neuroblastoma and often prompt an infectious work-up. Weight loss despite adequate feeding can be an insidious sign of widespread pathology.

Compression of cardiovascular or respiratory structures is a very serious symptom of a mediastinal mass. Compression of the superior vena cava may result in superior vena cava syndrome with significant venous distention of veins superior to the heart. The most common symptoms are dyspnea and fullness of the face. Other symptoms include cough, arm swelling, dysphagia, chest pain, stridor, headache, vision changes, and hoarseness [4].

Patients may also present with heart failure due to compression of one of the great vessels of the heart. Rarely patients will present with paraneoplastic syndromes like opsoclonus-myoclonus syndrome from a neuroblastoma.


Labs


Routine labs including complete blood count, electrolytes, creatinine, liver function tests, and coagulation studies are standard laboratory work-up.

Lactate dehydrogenase may be elevated in lymphoma. Alpha-fetoprotein and beta-human chorionic gonadotropin may be elevated in nonseminomatous germ cell tumor s. Neuroblastoma may have elevated catecholamine breakdown products, specifically urinary vanillylmandelic acid (VMA) and homovanillic acid (HVA).


Imaging


A chest x-ray is obtained as a first diagnostic test. An MRI may be helpful to diagnose some lesions, particularly neurogenic tumors. A CT scan is diagnostic for many lesions, and its delineation of structures and anatomic planes is superior for operative planning of lesion resection (Fig. 18.1).


Surgical Indications


When a pediatric mediastinal mass is discovered, a treatment plan should be put into place to diagnose the lesion and treat appropriately. Prenatal diagnosis of a suspicious mediastinal mass should prompt a plan for resection within the first year of life before symptoms develop [6]. Mediastinal masses diagnosed after birth should be treated, especially if symptomatic. Surgery is the primary treatment for all mediastinal masses except for lymphoma, which is treated with chemotherapy, and therefore tissue diagnosis is important to determine appropriate treatment [7]. Some masses may be unresectable at time of diagnosis due to invasion of non-resectable structures and should be biopsied first if possible to make a diagnosis to direct neoadjuvant chemotherapy or radiation.

Large, symptomatic masses should be biopsied under local anesthesia due to the significant risk of cardiovascular collapse under general anesthesia and positive pressure ventilation. Duplication cysts warrant excision as they are often symptomatic from mass effect on surrounding structures, can become infected, and have a potential for malignant transformation [8].


Controversies



Solid Posterior Mediastinal Tumors


The role of minimally invasive surgery for solid posterior mediastinal tumors, including neuroblastoma, ganglioneuroma, and ganglioneuroblastoma, has been an area of considerable debate. Much of the literature about pediatric mediastinal mass survival does not distinguish between thoracotomy and VATS. Temes et al. found a 5-year survival for lymphoma was 74 %, neurogenic tumors 67 %, and germ cell tumor 25 % after treatment with standard of care but did not compare VATS to thoracotomy in patients treated with surgery [9]. Multiple studies demonstrate that thoracic neuroblastoma survival rates are better than abdominal or pelvic neuroblastomas, with survival between 77 and 100 %, but these studies do not compare thoracotomy to VATS [1013].

Recent retrospective studies comparing VATS resection of neurogenic tumors versus open thoracotomy have reported equivalent rates of recurrence, survival, and disease-free survival with each group having similar tumor characteristics, including size and stage. In addition, thoracoscopic resection compared to thoracotomy has shown decreased perioperative morbidity such as less blood loss, shorter operative times, shorter hospital stay, and shorter duration of chest tube [12, 1417]. Concerns raised for an increase in port site recurrence have not been supported in the current literature [17].

Pediatric thoracic neurogenic tumors including neuroblastoma, ganglioneuroma, and schwannoma are good candidates for minimally invasive surgery if imaging shows it is resectable. Thoracic neuroblastomas will frequently enter spinal foramina, and aggressive attempts at en bloc resection can result in significant injury and morbidity. Visualization with thoracoscopy is superior and can aid in a safe resection up to the level of the foramina without unnecessary injury [12, 1416]. It is important to keep this in mind when trying to achieve surgically negative margins as to not cause excessive morbidity, especially for nonmalignant tumors such as ganglioneuromas, as this will not change prognosis or outcomes. Patients with tumors that are not resectable may benefit from biopsy to provide tumor biology and staging to direct neoadjuvant therapy. Biopsy may also be done to direct neoadjuvant therapy in an unresectable tumor that may later become resectable and amenable to minimally invasive resection.


Operative Considerations



Anatomy


Evaluation of the anatomy is critical prior to surgery. Cross-sectional imaging will allow you to assess the extent of disease and determine resectability. Unresectable tumors will invade into the great vessels, pericardium, lung, or spinal cord. Foregut duplication cysts will share a wall with its tissue of origin.


Anesthesia


It is important to have a clear anesthetic plan when preparing for surgery. Having an anesthesiologist experienced with pediatrics and minimally invasive thoracic surgery is recommended. Acceptable perioperative antibiotics include appropriately dosed cefazolin, ampicillin-sulbactam, vancomycin, or clindamycin [18].

General anesthesia is poorly tolerated in children with large mediastinal masses because their airways are more collapsible than those of adults. These factors, combined with decreased muscle tone and the supine position, increase the intrathoracic pressure and can occlude airways or prevent return of blood flow to the heart [19].

It is recommended to have a discussion with the anesthesiologist about the anesthetic plan prior to entering the operating room. Single lung ventilation may be used but is not always necessary. A double lumen tube can be used in children that are 8 years old or large enough for a 6.0 cuffed endotracheal tube, but smaller patients may require either single bronchus intubation or the use of a bronchial blocker. It is recommended that either of these techniques be done under direct visualization and placement confirmed with fiber optic bronchoscope. Insufflation of the thorax with 5–8 mmHg of CO2 is usually well tolerated and is often sufficient to deflate the lung. If insufflation is used, the anesthesiologist should be vigilant about monitoring for tension pneumothorax physiology and be prepared to alert the surgical team to desufflate immediately [20].


Room Setup


The room should be set up to easily transfer the patient to the operating table. Anesthesia is located at the head of the bed. The surgeon stands on the side of the patient opposite the pathology. The assistant stands above or opposite the surgeon. The surgical technologist is positioned near the foot of the bed on the side of the surgeon. It is ideal to have multiple video displays in line with the pathology facing the surgeon and the assistant.


Principles of Patient Positioning


Correct positioning of the patient is critical to the success of the operation. Gravity should be used to optimize exposure. The patient is positioned laterally with the lesion being as perpendicular to gravity as possible. Anterior masses are best approached with the patient in lateral decubitus and rolling the patient to be partially supine. Likewise, exposure to posterior masses benefits from the patient being tilted toward the prone position. Inferior masses benefit from Trendelenburg positioning, while superior masses benefit from reverse Trendelenburg. Towel or gel rolls are helpful in supporting smaller patients, while a beanbag should be considered for larger patients. Ensure that the arms are placed on arm boards and are not under stretch. The break in the surgical bed should be placed at the space between the inferior border of the lateral rib cage and the iliac crest to facilitate opening the rib spaces. A towel roll beneath the small child or neonate may be an adequate alternative to a break in the bed. When the patient is positioned, ensure that there is adequate clearance to manipulate instruments from the desired trocar positions.


Instruments


Standard laparoscopic instruments of appropriate size are sufficient for resection or biopsy of most mediastinal masses. Devices such as monopolar cautery via hook or scissors, a sealing device, or ultrasonic energy device are helpful to work with and can be chosen based on surgeon preference. In smaller kids, 3-mm trocars, instruments, and cameras may be used. There is a 3-mm sealing device that is available and that is helpful in the neonatal population. If a stapling device will be used, it is possible to use a 5-mm stapler, but otherwise consider which 5-mm port may be upsized to a 12-mm port to allow this if necessary. The smaller children have small rib spaces, and posterior rib spaces may be too small to comfortably place a 12-mm trocar. Also consider how you will remove the surgical specimen. Removing the specimen through a 5-mm incision is sometimes possible when the trocar has been removed.


Placing Trocars


Steps for placing trocars will use the same technique for each type of procedure but location of trocars will vary based on location of the mass. Local anesthesia is injected at the site of trocar placement by first feeling the rib inferior to the location with the needle then moving superiorly and injecting the inter-rib space. A small incision is made and the thorax can be entered with an open technique using a curved clamp or with a Veress needle. Insufflation to a pressure of 5 mmHg is tolerated well and assists with lung deflation. If using a Veress needle, dilatable expandable trocars are deployed after insufflation otherwise a regular trocar is placed. Insertion of a 3- or 5-mm 30-degree scope to view the location of the surgical target will help guide subsequent trocar placement. Two additional 3- or 5-mm ports should be placed under direct vision in a position that will allow triangulation. Trocars should be placed at least the distance of a closed fist away from one another, one trocar on the right and left of the camera. When placed under direct visualization, trocars can be placed in the posterior axillary line as high as the scapula allows and as low as the ninth or tenth intercostal space. Additional ports can be placed as needed, or 3-mm instruments can be placed through a stab incision without use of a trocar.


Steps for Thoracoscopic Approach to Mediastinal Mass



Anterior Mediastinal Mass Biopsy or Excision



Anesthesia


From an anesthesia perspective, masses located in the anterior mediastinum are the most problematic, and mediastinal masses overall carry a complication rate from 9.5 to 15 % [21, 22]. Retrospective studies of anesthetic complications revealed the strongest predictor of complications to be evidence of tracheal or vascular compression, infection, and three or more respiratory signs or symptoms [22]. Another study found the presence of stridor was the only reliable symptom of prognostic value to predict poor tolerance to general anesthesia [22]. A thorough physical exam should be performed to determine if the patient is a candidate for anesthesia based on symptoms of vascular compression, shortness of breath, stridor, and any ongoing oxygen requirement. If the patient is unsafe for general anesthesia, an open biopsy under local anesthesia should be considered.


Positioning


After induction of general anesthesia, perioperative antibiotics are given, and preparations for single lung ventilation are completed; the patient is placed in the lateral decubitus position, heavily favoring a list to the supine position. The anesthesiologist is instructed to switch to single lung ventilation. A 5-mm trocar placed in the fourth or fifth intercostal space in the posterior axillary line is useful for visualization of lesions in the anterior mediastinum. Triangulating the other two trocars also in a more posterior position will help to work anteriorly. The surgeon will stand on the posterior side of the patient with the assistant standing above or opposite to hold the camera.

A336954_1_En_18_Fig1_HTML.jpg


Fig. 18.1.
CT scan of a large anterior mediastinal mass [5].


Biopsy


See the above anesthesia section for considerations if a patient can safely undergo a biopsy under general anesthesia. After entrance into the chest, attachments can be freed up with sharp and blunt dissection to adequately visualize the lesion. Pleural adhesions are best released with blunt dissection, but it is valuable to have sharp dissection, electrocautery, or an energy device available [23]. When the lesion is encountered, a biopsy location should be chosen that is not in close proximity to any vascular structures. A figure-of-eight silk suture in the biopsy target can facilitate exposure with minimal damage to the specimen [20]. To minimize cautery artifact, sharp dissection should be used to remove the specimen, and then cautery can be used as needed for hemostasis. The specimen will be significantly smaller than what appears on the magnified laparoscope; therefore, it is important to ensure that enough of a specimen is taken to achieve a diagnosis. If there is any question, frozen specimens for pathology are recommended. The specimen can be removed directly through a trocar or through a thoracoscopically deployed specimen bag.

Only gold members can continue reading. Log In or Register to continue

Oct 25, 2017 | Posted by in PEDIATRICS | Comments Off on Thoracoscopic Approach to Pediatric Mediastinal Masses
Premium Wordpress Themes by UFO Themes