The provision of sedation inpatients with anterior mediastinal mass may be fatal without appropriate preparation

The provision of sedation inpatients with anterior mediastinal mass may be fatal without appropriate preparation: Excerpt from Avoiding Common Pediatric Errors

Author: Renée Roberts, MD

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The mediastinum is comprised of superior, anterior, middle, and posterior compartments; however, masses in the anterosuperior compartment of children can be extremely unstable and challenging for caregivers. A mass in this location may result in life-threatening airway obstruction, and can arise unexpectedly at any time and cause cardiac or pulmonary artery compression, or acute pulmonary edema from superior vena cava syndrome (SVCS), all of which represent true emergencies that mandate prompt treatment.

Compared with an adult, small decreases in a child's tracheal diameter produce larger decreases in cross-sectional area and airway resistance. The most common presentation of an anterosuperior mediastinal mass is stridor, dyspnea, and cough due to direct compression of the tracheobronchial tree. Often these children even require oxygen at presentation. Examination may demonstrate reduced breath sounds or rhonchi on auscultation, tachypnea, prolonged expiration, accessory muscle use, or cyanosis. However, patients may not be symptomatic and plain chest radiographs may not reveal the presence of airway compromise. Some studies, such as pulmonary function testing, can help to predict airway complications if they demonstrate flattened flow volume loops where expiratory flow is significantly diminished. Cardiorespiratory complications may occur abruptly in these patients and are often not related to mild preoperative symptoms and roentgenographic evidence.Extrinsic compression of the trachea or mainstem bronchi can cause significant airway obstruction and is a cause of death or morbidity with induction of or emergence from sedation or anesthesia. It is also important to understand that there is most likely some degree of SVCS in all children with anterosuperior mediastinal masses, which also can cause severe complications with any sedation.

Clinical manifestations of severe SVCS include variable degrees of face, neck, and upper thorax swelling; external jugular and superficial chest vein distension with possible cyanosis; and plethora. Cardiac orpulmonary artery compression and acute pulmonary edema can represent the initial clinical signs in previously healthy children. Upper body venous hypertension impedes lymphatic drainage, often leading to lymphedema or chylothorax. Although venous pressures are raised, it is not uncommon to find that edema and plethora are more impressive than large surface vein dilation. The most common cause of SVCS is surgery for congenital heart disease; the second most common cause is anterosuperior masses. Usually these masses are malignant lymphomas (usually found in adolescents) or germ cell tumors (children). Two thirds of the germ cell tumors are benign teratomas.

Because of the underlying pathophysiology of anterosuperior mediastinal masses, children may develop severe homodynamic compromise after sedation, induction of anesthesia, institution of positive pressure ventilation, or supine positioning. Compression of the right ventricular outflow tract or main pulmonary artery is probably more common than realized. In the supine position, the right ventricular outflow tract is the most superior cardiac structure. Additionally, the right ventricle is a low-pressure chamber and is more sensitive to compression than the higher-pressure ascending aorta. The right ventricle can usually compensate for moderate increases in pulmonary afterload. Adverse positioning, induction of anesthesia, hypovolemia, and reduced cardiac contractility may attenuate compensatory mechanisms. The additive effects of general anesthetics and sedation or positioning during diagnostic procedures may contribute to worsen the airway obstruction, leading to fatal cardiorespiratory failure. Sedation even for biopsy or excision of the mass is associated with a high risk for severe airway obstruction, hemodynamic compromise, and death.

Rapidly evolving symptoms of respiratory compromise from an anterior mediastinal neoplasm can occur even after the trachea has been secured through intubation. In addition, circulatory compromise becomes clinically apparent when compression of the great vessels occurs despite airway patency. As the tumor size increases, the trachea, mainstem bronchi, and major vessels may be exposed to an increasingly positive pressure. Any positive pressure ventilation can cause dynamic hyperinflation and resulting auto-positive end-expiratory pressure (auto-PEEP) because of expiratory gas flow obstruction. With sufficient elevation of intrathoracic pressure, the gradient for venous return is reduced, and right ventricular pressures are reduced, worsening the extent of vascular obstruction. Intraoperative deaths have beenreportedwithout evidenceof tracheal obstruction butwith cardiac compression or pulmonary artery compression or encasement demonstrated atautopsy.Oncethesecomplicationsoccur,thedeath rateappearstobehigh.

Initial treatment efforts of a child with a symptomatic anterosuperior mediastinalmassshouldbetowardpatientstabilization.Temporarysupportive measures, such as elevation of the head, oxygen, diuretics, and steroids may improve symptoms of SVCS. All children should receive cardiovascular monitoring.Spontaneousbreathingshouldbemaintainedifclinicallyacceptable, and sedation and muscle paralysis should be avoided. For diagnosis, the least invasive procedures should be performed under local anesthesia, avoiding the added risks of general anesthesia. Before any procedure, a thorough evaluation and preparation needs to be done by an anesthesiologist and the operating room team from pretreatment to prevent bronchospasm, with large bore intravenous (IV) catheters and arterial catheters and special wire reinforced endotracheal tubes of different sizes as well as fiberoptic, and jet ventilation capability, if needed. Because the use of awake fiberoptic techniques is limited in the pediatric population, volatile agent or IV induction is usuallythetechniqueofchoice.However,evenunderthebestcircumstances, adverse events occur especially in children with a tracheal area of <50%.

Ventilation after intubation is also complex, with several different approaches. Handling emergence, extubation, and postoperativecare must also be carefully planned. Severely symptomatic patients may require empiric pretreatment before any diagnostic procedures can be safely performed.

In a closed-claims database of the United Kingdom Medical Defense Union, eight adverse events were reported related to anterior mediastinal masses; six were younger than 8 years of age. The patients were booked for diagnostic biopsy of a mass—a trivial procedure. All eight cases suffered severe brain damage or death. A common theme was a bronchospasm or difficultywithventilation.Itmaybetemptingtosedatepatientswitha"benign" appearing mediastinal mass for a simple procedure; however, the very high risk of adverse complications makes children with a mediastinal mass a significantsedationandanestheticrisk.Becausesedationandgeneralanesthesia comprise the two ends of a continuum of states ranging from minimal sedation(anxiolysis)throughgeneralanesthesia,itisimperativetorealizethatfor any patient, itis notalways possible to predicthowan individualwill respond to the administered medications. Therefore, practitioners targeting a given level of sedation should be able to rescue patients whose level of sedation becomes deeper than initially intended (i.e., rescue patients who enter a state of general anesthesia). Given the risks involved with airway obstruction and underlying SVCS in the case of a child with an anterosuperior mediastinal mass, any procedure should be carefully planned with an anesthesiologist.

Suggested Readings

American Society of Anesthesiologist Task Force on Sedation and Analgesia by Non- Anesthesiologists. Practice guidelines for sedation and analgesia by non-anesthesiologists. Anesthesiology. 2002;96(4):1004–1017.
Narang S, Harte BH, Body SC. Anesthesia for patients with a mediastinal mass. Anesthesiol Clin North Am. 2001;19(3):559–579.
PiastraM,RuggieroA,CarestaE, etal.Life-threateningpresentationofmediastinalneoplasms: report on 7 consecutive pediatric patients. Am J Emerg Med. 2005;23(1):76–82.

Book Source Details

• Book Title: Avoiding Common Pediatric Errors
• Author(s): Anthony D Slonim MD, DrPH; Lisa Marcucci MD
• Year of Publication: 2008
• Copyright Details: Avoiding Common Pediatric Errors, Copyright © 2008 Lippincott Williams & Wilkins.

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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.

More About This Book: Title: Avoiding Common Pediatric Errors Authors: Anthony D Slonim MD, DrPH; Lisa Marcucci MD Publisher: Lippincott Williams & Wilkins Copyright: 2008 ISBN: 0-7817-7489-6

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