Anaesthetic challenges for a patient with huge superior mediastinal mass in prone position

Abstract

Anaesthesia for patients with huge mediastinal mass is very challenging due to the cardiorespiratory embarrassment that may occur. We present a patient with this condition, which was complicated by total airway obstruction, intraoperatively. We discuss the importance of patient positioning and the role of spontaneous ventilation.

Background

Anaesthetic management in patients with mediastinal mass is an extremely daunting task. Many perioperative complications including total airway obstruction, hypotension and asystole may occur due to compression of vital structures in the mediastinum. Hence, anaesthetists must be clever in drawing clear structured plans when managing this patient group to prevent fatal outcomes. We demonstrate our anaesthetic management on a patient with a huge superior mediastinal mass undergoing a spine surgery.

Case presentation

A 40-year-old man (60 kg, 170 cm) with a 10-year background of stage 2 nasopharyngeal carcinoma (NPC), presented with sudden onset of bilateral lower limb weakness for 3 days and mid-thoracic back pain. He denied any history of trauma. He had not been able to lie flat for 1 week as he felt short of breath and thus, had to be propped up with two pillows during his sleep. He was the sole bread winner for his young family. With regards to the NPC, he had completed chemoradiotherapy 2 years ago and was on regular 6 monthly follow-up with no local nor metastatic findings.

On examination, his vital signs were stable. He was not dyspnoeic nor had stridor when propped up at 45° position. There was bilateral lower limb power of zero and sensation was reduced inferior to the level of T6. Systemic examinations were unremarkable with a Mallampati score of 2. He had good neck flexion and extension. There was no mass seen at his chest, neck or back.

• A preoperative chest X-ray (CXR) revealed a widened mediastinum (figure 1).

• MRI of the spine showed multilevel spinal bone metastasis with spinal cord oedema and stenosis, which was worst at the level of thoracic 3–4 (T3–T4).

• Coronal and sagittal views of MRI neck and thorax showed a coincidental huge superior mediastinal mass measuring 9 cm × 6.6cm × 8.5 cm extending from T2–T6 levels which encapsulated bilateral subclavian veins. It caused a critical tracheal narrowing at the level of T4 with a horizontal diameter of only 8 mm (figures 2 and 3). In addition, there were multiple ill-defined lesions seen at the right adrenal gland and liver.

• He was anaemic with haemoglobin of 7.8 g/dL (normal values: 13.0–15.0 g/dL).

• The liver function tests showed slight elevation of alanine transaminase at 117 IU/L (normal values: 5–40 IU/L) and aspartate transaminase of 46 IU/L (normal values: 5–40 IU/L).

• Other parameters, including the arterial blood gases and phaeochromocytoma workup, revealed normal values.

Figure 1.

Preoperative chest X-ray showing a huge mediastinal mass.

Figure 2.

Coronal view MRI showing the mass extending from T2–T6 levels.

Figure 3.

Sagittal view MRI showing acute tracheal narrowing at T4 level.

Differential diagnosis

The provisional diagnosis was recurrent NPC with distant metastasis involving the spine, liver, right adrenal gland and superior mediastinum.

Treatment

Initially, he was advised for palliative care only, as per suggestion by oncology team. However, the patient begged for a surgery to be done as he had to fend for his wife and three young children. After a thorough consideration, he was posted for an emergency posterior spinal instrumentation and decompression at T3/T4 level in prone position.

An urgent contingency plan was drawn between the patient, anaesthetist, radiologist, orthopaedic surgeon, cardiothoracic surgeon and otorhinolaryngologist (ORL), focusing on the anticipated difficult intubation and ventilation with cardiorespiratory embarrassment during induction and maintenance of anaesthesia. The team agreed that should the airway management failed, the surgery would be cancelled, and for palliative care only. The anaesthetic plan was to intubate the patient using awake fiberoptic intubation (AFOI) without muscle relaxants. The ORL team would be on standby for jet ventilation or rigid bronchoscopy. If all these measures failed, the cardiothoracic team would perform sternotomy and cardiopulmonary bypass to lift the compressing mediastinal mass.

A very high risk written consent was obtained from the patient. Subsequently, he was fasted for 6 hours prior to the surgery. Intraoperative monitoring as per American Society of Anaesthesiologist guideline was set up. In preparation for AFOI, his airway was anaesthetised with lignocaine 2% nebulisation of 100 mg and xylocaine 10% sprayed once at each tonsillar bed and the pharyngeal wall (30 mg in total) respectively. Intravenous glycopyrrolate 200 μg was also given prior to the AFOI as antisialagogue. Additionally, a loading dose of dexmedetomidine 1 μg/kg was given over 10 min followed by maintenance at 0.2–0.3 μg/kg/hour.

AFOI was conducted via the oral route using spray-as-you-go method. Lignocaine 2% (20mg) was sprayed at arytenoids, valeculla and epiglottis. Another 20 mg was sprayed once the fibrescope had entered the trachea. It was pushed deeper towards the carina and the right and left bronchi to observe for lumen patency and obstruction. There was no compression visualised and the flexometallic (FM) endotracheal tube (ETT) sized 7.0 mm was gently railroaded towards and reached the carina initially. Intravenous propofol 30 mg was given and sevoflurane dose was dialled up to achieve a minimal alveolar concentration (MAC) of 1.0. Airway pressure (AP) was noted to be at 17–19 cmH₂0 generating tidal volumes (TV) of 350–400 mL under Synchronised Intermittent Mandatory Ventilation (SIMV) mode. The FM ETT was gradually withdrawn by 2 cm guided by the fibrescope and the cuff was reinflated; AP and TV remained the same and bilateral air entry was equal. It was anchored at 22 cm from incisors safely. The left radial artery and right femoral vein were cannulated for intraoperative monitoring and fluid resuscitations, respectively. A fibrescope was introduced again prior to turning the patient prone and we were convinced of the airway patency distal to the ETT and beyond the carina.

The patient was carefully pronated and put onto a spine table. Anaesthesia was deepened with sevoflurane MAC of 1.5 and dexmedetomidine at 0.7 μg/kg/hour with stable hemodynamics. A good support was provided onto the forehead, chest and limbs. For the first 20 min after positioning, the AP increased only slightly to 20–22 cmH₂0 but TV maintained at around 300–350 mL with equal air entry bilaterally.

While the teams were adjusting the patient’s position, the general anaesthesia (GA) machine started showing very high AP of 38–40 cmH₂0 and TV of 40–50 mL. The oxygen saturation (SpO₂) dropped to 92%–93% with poor lung compliances during manual bagging with 100% oxygen. The impression at that moment was kinked ETT or bronchospasm. Troubleshooting was done to rule out both differential diagnoses. The next immediate diagnosis was total airway obstruction secondary to collapsed airways. A fibrescope was immediately inserted into the FM ETT to look for intraluminal collapse in prone position. To our horror, the fibrescope was only able to be inserted up to 20 cm of length and subsequently got stuck at the end of the FM ETT. We were unable to go beyond it towards the carina, despite repetitive attempts to push through. The tracheal tissues were seen kissing each other distally (figure 5figure 4). There were no tracheal air bubbles visualised. A total airway obstruction had occurred, and the patient desaturated to 70%–75% with blood pressure (BP) of 132/75 mm Hg and pulse rate (PR) of 92 beats/min.

Figure 4.

Fibreoptic view in prone position showing kissing tracheal tissues.

We quickly supinated and sat the patient up in the best comfort position. Sevoflurane was stopped so that the patient could regain consciousness. During that period, the patient desaturated further to 50% and became cyanosed but BP and PR remained stable. The ORL and cardiothoracic surgeons immediately scrubbed up in preparations for a bypass. Despite aggressive manual bagging with 100% oxygen, we were not able to reinflate both lungs. Fortunately, we successfully pushed the FM ETT deeper to 28 cm during our last few attempts of resuscitation. During the process, patient was gagging and had his own spontaneous breathing. We were lucky that we managed to push in and anchored the ETT at 28 cm safely. At this time, patient started to regain his consciousness slowly and was having irregular respiratory effort. It however had brought up the saturation fast to 100% within 10 min and AP normalised to 18-20 cmH₂0 with SIMV. The TV generated was good at 400–450 mL with stable haemodynamics. Patient recovered and responded to simple commands in the OT.

Outcome and follow-up

The surgery was cancelled, and the patient was sent to Intensive Care Unit (ICU) for stabilisation and extubated in a full awake manner 2 hours later. A repeated CXR showed an enlarged mediastinal mass, more on the right side with no new pulmonary opacities.

A family conference involving the anaesthetist, orthopaedic surgeon, otorhinolarnygologist, cardiothoracic surgeon, oncologist, physician and counsellor was held to discuss regarding the complexity of his illness. The patient finally agreed for palliative care only. He was given good psychological and counselling support from the team.

Discussion

Mediastinal masses are extremely rare occurrences and more common to occur in young middle age adults.^{1 2} The most common causes in adults are non-Hodgkin lymphomas, thymomas and Hodgkin lymphoma.^{2 3} Patients with a huge superior mediastinal mass poses a great challenge to anaesthetists. It may impinge on adjacent organs such as great vessels and heart causing hypotension and arrhythmias. Compression on bronchus and trachea may lead to dyspnoeic at rest, as can be seen in our patient. Béchard et al mentioned that symptomatic patients with mediastinal masses often demonstrate cardiorespiratory complications perioperatively.⁴ Good preoperative assessment, focusing on these symptoms and its best position to alleviate it, is crucial.

The net effect of a mass depends on the balance between the intrathoracic pressure and gravitational effect. A spontaneously breathing patient in a supine position will see the negative intrathoracic pressure effect pushing the mass upwards, relieving its compressive effect. In the sit up position, gravity pulls the tumour rostrally towards the abdomen, bypassing the mediastinal structures. Pressure effect will be lowest at the patient’s most comfortable position and decompensation will be minimal.⁵ This is often used during induction of anaesthesia or intraoperative catastrophe, as in our case.

Patients with mediastinal masses have a 7%–18% incidences of fatal airway obstruction during GA.⁶ Patients should be carefully counselled, and high-risk consent are obtained when surgeries are done under GA. Factors that reduce the intrathoracic pressures such as GA, muscle relaxants and positive pressure ventilation will shift a balance in favour of gravitational effect. GA reduces the lung mechanics and relaxes the airway, causing it to lose its bronchial tone.⁷ Muscle relaxants may further complicate these. The tumour may collapse and compress the trachea or bronchus, causing difficulty in ventilation and severe hypoxaemia, especially in supine position.

In the prone position, gravity will pull the mass onto the sternum, relieving its pressure effect on the mediastinal structures.^{8 9} This position also physiologically improves lung ventilation and perfusion thus reducing ventilation-perfusion mismatch.¹⁰ However, our patient sustained total airway obstruction during prone position. The most likely explanation is apnoea and loss of airway tone. The huge mass might have caused tracheomalacia thus softening the tracheal cartilages and completely compressing it. Another probability is that the pillow added extra pressure onto the mediastinum, causing it to crash retrogradely onto the trachea and bronchus.

Anaesthesia for patients with a huge superior mediastinal mass needs an immense interdepartmental perioperative planning. An MRI thorax and neck will delineate the size, origin of the mass and identify the narrowest level of tracheobronchial compression. Ideally, an AFOI should be performed to directly visualise the tracheobronchial tree.¹¹ Patient should not be paralysed to avoid airway compression. A FM ETT should be used instead of the normal polyvinylchloride for extra flexibility and durability. Unfortunately, in our patient, the mass completely collapsed onto our FM ETT, causing total airway obstruction. This suggested that FM ETT should be used with caution in patients with a huge mediastinal mass, as it may not necessarily guarantee the ability to sustain any external pressures to maintain airway patency.

The main aim of intubation is to bypass the level distal to the critical obstruction, which may sometimes require endobronchial intubation with a long microlaryngeal tube. A skilled ORL in handling rigid bronchoscopy, jet ventilation and bronchial stenting will allow prompt life saving measures. The cardiothoracic team should be ready to perform an immediate sternotomy to lift the mediastinal mass to alleviate compression and improve ventilation.

In this patient, we performed AFOI which was supplemented with dexmedetomidine as it possesses excellent anxiolytic and analgesic properties. Sevoflurane maintains spontaneous ventilation and bronchodilation without causing apnoea. We maintained high vigilance throughout our procedure, focusing on the AP and TV, with our focus on preventing total airway collapse. Dexterity on handling AFOI in supine and prone position comes in handy during troubleshooting.

Patient’s perspective.

Nobody can understand my position as the sole bread winner for my small family with two very young children. I dared the risk to do this extremely high-risk surgery so as that I can return to work soonest and able to fend for them. God’s willing, that the surgery was unable to proceed. Fortunately, and most importantly, I survived the scary turmoil in the operating theatre. I would like to thank all parties involved for saving my life. I accepted this fate and appreciated my life with family.

Learning points.

• Extreme vigilance and preparations are needed in anaesthetising patients with huge superior mediastinal masses.

• Urgent preoperative contingency plans should be drawn involving the patient, experienced anaesthetists, otorhinolaryngologist, cardiothoracic surgeon and radiologist.

• Awake fiberoptic intubation, avoidance of muscle relaxants and maintenance of spontaneous respiration are gold standard to prevent total airway obstruction.

• Intubations should be aimed to bypass the narrowest part of the tracheobronchial tree.

• Patient positioning to alleviate compressive symptoms and complications are based on case-to-case basis and is not one size fits all.