Although the mediastinum has been described to be divided into different compartments, the demarcation between the compartments are arbitrary and a space occupying lesion from one compartment may easily compress the structures of other compartments [16
This effect is more seen in children because of more incidence of neurogenic tumour [17
], small thoracic cavity size, more compressible cartilaginous structure of the airway, reduced cardiopulmonary reserve or difficulty in obtaining a history of positional symptoms in children [16
]. Some study found higher mortality
in children [20
], whereas according to some there is no significant difference in mortality in different age group [22
]. Another definite problem in pediatric age group is institution of femoro-femoral bypass under local anesthesia. Authors suggest judicious use of ketamine or sevoflurane to assist the procedure.
Patients may be asymptomatic at presentation. But during induction or even with mild preoperative sedation, there may be reduction of muscle tone and/or protective reflexes which may culminate in tracheobronchial compression and precipitation of severe hypoxia. Severe respiratory complications during anesthesia induction in a patient with mediastinal mass may be attributed to several factors. Firstly, reduction of lung volume with commencement of general anaesthesia cause decrease in tracheobronchial diameter [16
]. Secondly, larger airways become more compressible due to reduction of smooth muscle tone [16
]. Thirdly, with diaphragmatic paralysis or paresis there is elimination of normal transpleural pressure gradient which acts to maintain airway patency during inspiration [18
]. Fourthly, loss of tone of the chest muscles lead to loss of structural support to the airway [16
]. LMA insertions and all other modalities practised in standard difficult airway algorithm may be of no value because airway obstruction occurs distally [20
]. Prolonged compression of trachea may result in tracheomalacia [7
], which may interfere with weaning from ventilator.
Cardiac problems may arise from compression over the heart, compression of pulmonary artery, pericardial effusion or direct myocardial involvement from mediastinal masses. Diastolic filling may be compromised due to mass effect or pericardial effusion. Cardiac compressions may result in rhythm disturbances and syncopal attack [7
]. Presence of pericardial effusion has been proved to be definitely associated with adverse outcome in intraoperative period [2
]. Compression of pulmonary artery (PA) may obstruct right ventricular outflow, reduce pulmonary blood flow and severely diminish venous return to left atrium [9
]. These patients may present with a flow murmur and outcome may be fatal [13
]. Dysrrhythmia may occur due to pericardial or myocardial involvement or secondary to respiratory or hemodynamic problems [13
]. Large lymphomas may exert a tamponade like effect on the heart. Anesthetics may reduce cardiac contractility and severely diminish cardiac output. Keon [25
] reported a patient with mediastinal mass and symptoms mimicking pericardial tamponade or constrictive pericarditis suffered from sudden severe cardiovascular collapse and death when halothane induction compromised myocardial contractility. Pulmonary edema may occur due to various causes during perioperative period and complicate the situation. Eicher et al. [26
] have described two cases of pulmonary edema due to obstruction of pulmonary venous flow.
Problems may be aggravated or new complications may arise with change of posture, airway manipulation, even institution of CPB. Cantor and Fitzsimons [27
] have described a 40 year old patient presented with anterior mediastinal mass compressing the RVOT and SVC. There was no preoperative symptom of compression. But with initiation of cardiopulmonary bypass and reduced venous return through systemic veins, compression on the major vascular structures aggravated and cerebral oxygen saturation dropped. They managed the situation with neck flexion and relieving the obstruction on SVC. Central venous access may be difficult due to compression of SVC [9
]. Factors statistically significant associated with mortality during hospitalizations were sepsis, superior vena cava syndrome, and massive pleural effusion [28
]. Although the anesthetic management problems may be categorized as patient related, anesthesia related or surgery related, the problems are interrelated and combined factors play role during occurrence of complications.