Mediastinal mass

Symptoms in children with mediastinal tumors are more likely to be present because the relatively elastic conductive airways increase the risk of external compression.

In an anesthetized patient breathing spontaneously, these mechanical processes are essentially the same. Nevertheless, the impact of inhalational or intravenous anesthetics (except for ketamine) on respiratory muscle tone, alterations in thoraco-abdominal dimensions and central blood volume, cephalad movement of the diaphragm and an ↑ closing capacity may result in ventilation-perfusion mismatching

supine → FRC ↓ by 0.7-0.8L
GA → FRC further ↓ by 0.4-0.5L
Consequently, dynamic airway resistance is increased due to reduced lung volumes, whereas pulmonary compliance is decreased

In mechanical ventilation with volume or pressure control, the diameters of the conductive airways increase during inspiration, thereby facilitating the flow of inspiratory gases. During expiration, the cross-sectional area decreases due to elastic recoil, which induces higher dynamic resistance. An augmented closing capacity may precipitate air trapping, hyperinflation of the lung, auto-positive end-expiratory pressure (PEEP), and hemodynamic collapse

Safe (low risk)	Uncertain (intermediate risk)	Unsafe (high risk)
Asymptomatic patients	Patients with moderate clinical symptoms	Symptomatic patients
CT and dynamic evaluation with negative results	Asymptomatic patients with abnormal dynamic evaluation Patients without the possibility of diagnostic evaluation Tracheal CSA < 50% in adult patients Tracheal CSA < 30% in pediatric patients PEFR > 50%	MMS clinical signs present and positive diagnostic evaluation Tracheal CSA < 50% in adult patients Tracheal CSA < 30% in pediatric patients PEFR < 50%

References

Myths of anterior mediastinal masses

Perioperative Management of Patients With Mediastinal Mass Syndrome