Overview
Definition:
Mediastinal masses in children encompass a diverse group of congenital, neoplastic, and inflammatory lesions located within the mediastinum
Biopsy is often required for definitive diagnosis and subsequent management, necessitating careful anesthetic planning to mitigate risks, particularly airway compromise.
Epidemiology:
The incidence varies by age and mass location
Anterior mediastinal masses are common in children and adolescents, with teratomas and lymphomas being frequent etiologies
Posterior mediastinal masses are more often neurogenic tumors
Overall, mediastinal masses account for a small percentage of pediatric tumors but have significant morbidity and mortality if not managed appropriately.
Clinical Significance:
Mediastinal masses, especially large ones, pose a significant anesthetic challenge due to their potential to compress vital structures like the trachea and major airways
This can lead to intraoperative or postoperative airway obstruction, cardiorespiratory instability, and systemic complications
Expert anesthetic management is crucial for patient safety and successful biopsy.
Anesthetic Challenges
Airway Compression:
The primary concern is extrinsic compression of the trachea or bronchi, leading to reduced lung volumes, increased airway resistance, and potential for complete airway obstruction upon induction of anesthesia (loss of spontaneous muscle tone).
Vascular Compression:
Compression of great vessels (SVC, pulmonary arteries) can cause altered hemodynamics, reduced venous return, and pulmonary hypertension, impacting cardiovascular stability.
Phrenic Nerve Involvement:
Paralysis or paresis of the diaphragm due to phrenic nerve compression can impair spontaneous respiration and ventilation.
Positional Effects:
Supine positioning for induction can worsen airway compression
lateral or prone positioning may be necessary, adding complexity to anesthetic management and monitoring.
Fixed Pulmonary Vasculature:
Large masses can lead to fixed pulmonary vascular resistance, making ventilation-perfusion matching challenging and increasing the risk of hypoxemia.
Potential For Bleeding:
Highly vascular tumors can lead to significant intraoperative bleeding, requiring adequate blood product preparation and vigilance.
Preoperative Assessment And Preparation
Detailed History And Physical:
Assess for symptoms of airway compression: stridor, dyspnea, cough, dysphagia, hoarseness, or positional relief of symptoms
Evaluate for signs of SVC syndrome (facial swelling, engorged neck veins).
Imaging Review:
Thorough review of CT scans, MRI, and chest X-rays to delineate the mass size, location, relationship to airway and mediastinal structures, and vascularity
Assess for any signs of impending airway compromise.
Pulmonary Function Tests:
Consider PFTs in older children to assess baseline respiratory function, though they may be limited in the presence of significant obstruction.
Cardiac Evaluation:
Echocardiogram to assess for cardiac involvement or compromise, especially in cases of suspected vascular tumors or compression.
Airway Assessment Tools:
Ensure availability of difficult airway equipment, including various sizes of ET tubes, video laryngoscopes, fiberoptic bronchoscope, and supraglottic devices.
Anesthesia Team Consultation:
Early and comprehensive discussion with the pediatric anesthesiologist, thoracic surgeon, and pulmonologist to formulate a tailored anesthetic plan and discuss potential intraoperative challenges and contingency plans.
Informed Consent:
Discuss risks, benefits, and alternatives with guardians, emphasizing potential for airway instability and need for awake intubation if indicated.
Airway Preparation:
Consider premedication to reduce anxiety but avoid sedatives that significantly depress respiration
Nasal airways are generally avoided due to risk of bleeding into the mass.
Positional Planning:
Discuss optimal patient positioning for induction and maintenance, often involving awake fiberoptic intubation or awake nasal intubation in a sniffing position or even sitting upright.
Anesthetic Management Strategies
Induction Technique:
Awake intubation is the preferred method for most patients with significant mediastinal masses due to the risk of complete airway obstruction with inhaled or IV induction agents
Topical anesthesia of the airway is essential.
Intubation Technique:
Fiberoptic bronchoscopy-guided intubation is often used
A small, cuffed endotracheal tube should be selected and readily available
Once the tube is in place, it should be securely taped and confirmed with capnography and bilateral chest auscultation.
Ventilatory Strategy:
Gentle ventilation with low tidal volumes and adequate PEEP to maintain oxygenation without exacerbating airway pressure
Avoid positive pressure ventilation until the airway is secured if possible
Monitor for air trapping or dynamic hyperinflation.
Monitoring:
Continuous ECG, pulse oximetry, capnography, invasive arterial blood pressure, central venous pressure (if indicated), and temperature monitoring are essential
Neuromuscular monitoring is crucial for guiding muscle relaxant administration and reversal.
Pharmacological Choices:
Avoid agents that significantly depress spontaneous respiration or cause bronchodilation (which can mask airway obstruction)
Opioids and low-dose benzodiazepines may be used for sedation during awake intubation
Ketamine can be useful for its bronchodilatory and cardiovascular-preserving effects.
Maintenance Anesthesia:
Often maintained with volatile anesthetics at low concentrations combined with a balanced opioid/muscle relaxant technique, guided by invasive monitoring
Careful titration of anesthetic agents is key.
Reversal Of Neuromuscular Blockade:
Ensure complete neuromuscular recovery before extubation
Extubation is typically performed when the patient is fully awake and maintaining spontaneous respiration, ideally in a position that minimizes airway compression.
Postoperative Care
Extubation Criteria:
Extubation should only occur when the patient is fully awake, able to maintain spontaneous ventilation, protect their airway, and has adequate respiratory muscle strength
Close observation for any signs of airway distress is paramount.
Monitoring In Icu:
Close monitoring in an intensive care unit is usually required
Continuous pulse oximetry, frequent respiratory assessments, and vigilance for stridor or other signs of airway compromise are critical.
Pain Management:
Adequate pain relief is essential to promote deep breathing and prevent atelectasis
Epidural analgesia or patient-controlled analgesia (PCA) with opioids can be considered.
Positional Management:
Positioning to optimize airway patency and facilitate lung expansion
Head of bed elevation is often beneficial.
Bronchodilators And Suctioning:
Availability of nebulized bronchodilators and suctioning equipment for airway secretions
Humidified oxygen should be provided.
Readiness For Reintubation:
Anticipate and be prepared for potential reintubation if airway obstruction or respiratory failure develops
Having airway equipment readily accessible is crucial.
Key Points
Exam Focus:
The most critical anesthetic concern is airway obstruction due to mass effect
Awake intubation is the gold standard for induction in most cases
Prepare for difficult airway management and potential intraoperative complications.
Clinical Pearls:
Always review imaging meticulously to understand mass extent
Discuss the case extensively with the surgical team
Have a low threshold for maintaining spontaneous ventilation until the airway is definitively secured and assessed.
Common Mistakes:
Attempting mask induction or deep extubation in the presence of a potentially obstructive mass
Underestimating the risk of airway collapse
Inadequate preparation for a difficult airway
Insufficient monitoring or delayed recognition of airway compromise.