Anterior mediastinal mass: A dreaded challenge for anaesthesiologistsA case report

INTRODUCTION

The mediastinum hosts a diverse array of neoplasms with often rare histologies.^[1] These neoplasms can be benign or malignant and may originate from tissues such as the airway, pleura, thyroid, thymus, lung, pericardium, and lymphatics.^[2] Due to potential complications, these patients may often require anaesthesia for surgical procedures such as biopsy, staging laparotomy, and others.^[3] Large tumours cause significant cardiopulmonary complications through mass effects: airway obstruction, reduced lung volume, and compression of vital structures. “Mediastinal mass syndrome” (MMS) frequently complicates surgical and anaesthetic management.^[2]

CASE REPORT

A male patient, 66 years old, presented to the emergency department with a history of 10–14 days of abdominal pain. He had type 2 diabetes, hypertension, and coronary artery disease for 8 years, and was on oral glimepiride (2 mg), aspirin (75 mg), atorvastatin (40 mg), nicardipine (10 mg), and torsemide (10 mg). He was a chronic smoker for 40 years and reported dysphagia and dyspnoea in the supine position, relieved by sitting upright.

Airway evaluation suggested potentially difficult bag–mask ventilation, with a Mallampati grade III airway. Breath-holding time was 15–18 seconds, and left-sided breath sounds were reduced.

Superior vena cava syndrome was absent, and supine tolerability was noted. Cardiovascular examination was normal apart from clinical pallor.

Recent investigations revealed an uncontrolled diabetic status with glycosylated haemoglobin of 8.2% and haemoglobin level of 8 g/dl after one blood transfusion. The trachea appeared deviated to the right on the chest radiograph. Computed tomography scan revealed a heterogeneously enhancing soft tissue mass measuring 110×69×47 mm with internal echoes in the left hilar region extending into the mediastinum and closely abutting the oesophagus. It encased the left main bronchus and infiltrated the left main pulmonary artery. Another mass measuring 48×51×47 mm was seen in the superior mediastinum on the left side, closely abutting the left common carotid and left subclavian artery and encasing the left brachiocephalic trunk. Multiple enlarged enhancing lymph nodes were found in the preparatracheal, aortopulmonary window, and subcarinal region, along with metastatic deposits in bilateral adrenal glands. It was suggestive of lymphangitis-carcinomatosis. The right kidney was atrophic, suggestive of chronic pyelonephritis. Echocardiography revealed concentric left ventricular hypertrophy with an ejection fraction of 55%.

An emergency laparotomy was scheduled, and written informed consent was taken. An emergency airway cart was kept ready for an airway catastrophe. The patient was kept fasting for 8 hours. Two 20-G intravenous cannulae were secured. The baseline vital parameters included blood pressure 140/90 mmHg, pulse rate 107/min, peripheral oxygen saturation 94 % on room air, and 97% on a facemask with oxygen at 4L/min, and random blood sugar 117 mg/dl. The patient had a preoperative urine output of 50 ml. He was an intermediate-risk patient according to the classification given by Tan et al.^[4], and a combined thoracic segmental spinal with epidural was planned to be administered. The procedure was performed in the sitting position [Figure 1]. After local infiltration, an 18-G Tuohy needle was inserted at the T10-T11 level, guided by the loss-of-resistance technique using normal saline. An epidural catheter (20-G) was threaded through the needle, checked, and secured in place. A subarachnoid block was performed using a 25-G Quincke’s needle at the T11-T12 intervertebral space via midline approach. Injection ropivacaine 0.75% isobaric (15mg) with injection fentanyl (25 µg) was administered after confirming the free flow of cerebrospinal fluid. The desired level of blockade (T4-L1) was achieved. The patient was placed in a 10–15° head-up position, femoral central access was secured under local anaesthesia, and oxygen was supplemented at 4 L/min. Intraoperative monitoring remained stable, and one unit of packed red blood cells was transfused. Analgesia was maintained with 2-3 ml of injection ropivacaine 0.25% isobaric administered intermittently every 30 minutes epidurally and intravenous paracetamol infusion (1 g) over 20 minutes. The surgeons comfortably dissected and removed the mass [Figure 2]. The patient was shifted to the intensive care unit after completion of the surgery.

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Figure 1:

Segmental spinal with thoracic epidural in place and secured

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Figure 2:

Intraoperative view

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DISCUSSION

Compression of the main pulmonary artery is rare, as the aorta is a high-pressure vessel and bestows its protective effect. Still, compression of either the pulmonary trunk or one of the main pulmonary arteries poses significant risks such as sudden hypoxaemia, hypotension, or cardiac arrest due to MMS. Thus, compressive effects can develop severe life-threatening consequences during induction, which might require emergency extracorporeal bypass. Supine position, along with changes in chest wall muscle tone and the positive pressure ventilation during general anaesthesia, can significantly reduce pulmonary blood flow. Gravity acting across the anteroposterior chest cavity causes the mass to compress the tracheobronchial tree, disrupting mediastinal space balance. Nevertheless, immediate collapse after anaesthesia induction in patients with mediastinal masses involving the pulmonary artery has been documented.^[2]

Several authors have described the anaesthesia management of mediastinal masses.^[5-7] It is advised to maintain stroke volume (SV) and refrain from paralytic drugs. Progressive induction is preferable, and each agent should be used sparingly to retain SV. The decrease in functional residual capacity also affects mediastinal space balance.^[8] Loss of spontaneous ventilatory activity reduces the trans-pleural pressure gradient that distends intrathoracic airways and prevents collapse. Human mediastinal pressures are considerably lower with spontaneous ventilation, supporting this concept.^[9]

We utilised the segmental spinal anaesthesia technique in our patient. Nonetheless, segmental anaesthesia can offer several advantages.^[10] It calls for dural puncture at thoracic or higher lumbar levels with a low local anaesthetic drug dose, decreasing complications and haemodynamic instability. Low-dose block preferentially inhibits the sensory nerves over the motor ones, preserves the muscle tone and power in the leg, and this facilitates early ambulation, decreases anxiety, and increases patient satisfaction. It is believed to provide better analgesia than parenteral opioids, decreasing perioperative opioid requirement. Regional anaesthesia is preferred to avoid instrumentation of an already compromised airway, which is crucial if the patient falls into the intermediate-risk category.^[4] Respiration is not affected, as the diaphragm receives its motor nerve supply from the phrenic nerve that remains unaffected in the block. Additionally, the intercostal muscles, which are primarily involved in forced expiration, experience minimal blockade.

CONCLUSION

Anaesthesia for patients with large mediastinal masses remains a challenge for the anaesthesiologist due to life-threatening complications arising from the compression of the vital structures. Segmental spinal anaesthesia, when guided by comprehensive preoperative evaluation, meticulous planning, and well-defined emergency protocols, represents a safe and effective approach for major abdominal surgeries in patients with comorbidities.