Mediastinal masses compress the major airways and cardiovascular structures; cautious approach towards these patients is necessary before subjecting them to anaesthesia.[1] The incidence of complications related to airway obstruction with the use of general anaesthesia in patients with mediastinal masses has been reported in the past to be around 7-18%.[2] These values depict high-risk of cardiovascular and airway collapse post-anaesthesia induction especially in children.[34]
CASE REPORT
A 4-year-old female child, weighing 10 kg, diagnosed as a case of bronchogenic cyst was posted to undergo thoracotomy for excision of the cyst. Her primary complaints were recurrent chest infections since the age of 1 year and there was history of dry cough during the preanaesthetic evaluation. On auscultation, chest was clear with bilateral equal air entry and normal heart sounds. There were no features of airway or cardiovascular involvement in the form of postural dyspnoea, orthopnoea, dysphagia, syncope, cyanosis, palpitations or head and neck oedema. Routine haematological investigations were unremarkable. On chest X-ray posteroanterior (PA) view [Figure 1], there was mediastinal widening and on lateral view [Figure 1], trachea was markedly displaced anteriorly, but there was no apparent compression. Contrast enhanced computed tomography (CECT) chest revealed, a 5.7 cm × 4.6 cm × 2.8 cm cyst with undefinable borders in the middle mediastinum. Lesion extended from superior mediastinum (C7) to subcarinal region (T4, T5 vertebrae) in the tracheo-oesophageal groove causing anterior displacement of the trachea and right displacement of oesophagus. Spinal cord and thoracic vessels were not involved.
Chest X-ray lateral view shows anteriorly displaced trachea. Chest X-ray posteroanterior view shows a widened mediastinal shadowA left thoracotomy and excision of the cyst was planned. Standard monitoring including electrocardiogram (lead-II), NIBP, end-tidal CO2, pulse oximetry, temperature were instituted inside the operation theatre. Anaesthesia was induced with intravenous (iv) ketamine 25 mg, fentanyl 10 μg and glycopyrrolate 0.1 mg along with sevoflurane and ventilation with bag and the mask was confirmed. Suxamethonium 20 mg iv was given and ability to ventilate was reconfirmed. Trachea was intubated using 4.5 mm cuffed endotracheal tube and fixed at 16 cm mark at the lip after confirming bilateral equal air entry on auscultation. Anaesthesia was maintained with O2, N2O, sevoflurane and vecuronium. Analgesia was supplemented with morphine IV and paracetamol suppository.Right lateral position was given taking all precautions to protect eyes and pressure points. During dissection, there was no episode of hypotension or arrhythmias. Chest was closed after placing an intercostal chest tube. The intra-operative course was uneventful. At the end of the surgery, neuromuscular blockade was reversed with neostigmine and glycopyrrolate, and trachea was extubated after ensuring signs of adequate reversal. Post-operatively, the patient was monitored for signs of airway collapse. Post-operative analgesia was provided with paracetamol suppositories 8 hourly. The post-operative course was uneventful, and the patient was discharged from the hospital after 1 week.
DISCUSSION
Clinically, infants with bronchogenic cysts, mostly present with respiratory distress. In children, there is history of cough, dyspnoea, dysphagia and frequent chest infections whereas adults present with chest pain or dysphagia. Respiratory signs and symptoms are more in children due to relatively soft airways, which are more susceptible to compression, leading to partial collapse, emphysematous chest, and respiratory infections.[4]Relaxation of bronchial smooth muscles under anaesthesia increases the risk of compression of the airways since they are already made narrow by the external pressure of the mass.[5] Coupled with this, neuromuscular blockade adds to the risk of compression by decreasing the tone of the chest wall.[6] All these factors make anaesthesia for mediastinal mass a challenging situation wherein severe and life-threatening airway compromise can occur at any stage. The peri-operative risk of complications increases if the patients are symptomatic pre-operatively; this cannot be ruled out completely even in asymptomatic patients.[7] Hence, all patients should be thoroughly evaluated for the presence of compression, deviation or distortion of airways and great veins. Chest radiograph PA and lateral view, CT scan of the neck and thorax, barium study and echocardiogram should be performed in all these cases, especially in symptomatic patients. All these complications are more frequent in paediatric population, due to smaller airways and decreased cardiopulmonary reserve.[3]Awake fiberoptic guided intubation is the method of choice in adults but is not always practical in children. Inhalational induction or IV induction with ketamine has been proposed in order to maintain tone and spontaneous respiration so as to prevent airway collapse. However partially obstructed respiration, which may occur during an inhalational induction, can generate large negative pressures that tend to flatten further a trachea weakened by extrinsic compression.[5] Our patient had symptoms of cough and past history of stridor and dyspnoea. We used iv ketamine for a smooth induction, after which sevoflurane was added, no airway compromise was observed after deepening of anaesthesia, therefore iv suxamethonium was given to facilitate smooth intubation. Since, the mass was extending up to the subcarinal level, a 4.5 mm cuffed tube was negotiated beyond the carina into the right stem bronchus and then withdrawn ensuring the ability to ventilate at each step until bilateral equal air entry was confirmed.Use of muscle relaxants and institution of positive-pressure ventilation may result in catastrophic airway obstruction, as the increased gas flow across the stenosis decreases the intraluminal pressure leading to further tendency to collapse.[8] Hence, relaxation should be given only after ensuring adequate ventilation after induction. Long endotracheal tube, e.g. microlaryngeal tube (MLT) or rigid bronchoscope can be used to tide over this situation in which the narrowing is in the distal airway and were kept ready. Change of posture is also a useful manoeuvre, therefore, pre-operative, relation between dyspnoea and posture should be sought. In extremely high-risk cases, extracorporeal oxygenation using femoro-femoral bypass is an option.[7] In our case, the patient was symptomatic and there was significant tracheal deviation, but no compression on chest X-ray.
CONCLUSION
Pre-operative assessment of the degree of the airway and cardiovascular compromise by patient's symptomatology and investigations especially CT scan are imperative in cases of mediastinal masses. MLT and rigid bronchoscopes should be available and femoro-femoral bypass is an option in case of severe tracheobronchial and superior vena cava compression.
Figure 1