Depending on the location of the mediastinal mass, lying a child flat or using a rapid sequence induction protocol may cause cardiorespiratory arrest. As clinicians, we need to be prepared.
What causes a mediastinal mass?
The mediastinum is the segment of the thorax that includes structures vital to life – the heart, major blood vessels, and the airway. The way we understand mediastinal anatomy has recently changed, dividing it into three compartments based on location: pre-vascular, visceral and paravertebral.
You may find a mediastinal mass in any compartment where it may cause compression of any of the structures within. Some basic knowledge of the structures within each compartment can be helpful when considering differentials. Sadly, in children up to half of all masses are malignant. A biopsy is often ultimately required for a definitive diagnosis.
Why do we worry about the airway?
Mediastinal masses can compress adjacent structures within the mediastinum. They may cause reduced venous return and impaired lymphatic drainage but airway compression is of particular concern. Any reduction in the radius of the airway can massively increase the resistance to flow (Hagen-Poiseuille law for any clever physicists out there). This effect is more dramatic in children. They already have a smaller, more compressible airway.
In the awake child, muscle tone may stent the airway open. As soon as this is lost, the airway may collapse under the compression of the mass, occluding both the airway and major vessels. This can occur at the onset of anaesthesia and may lead to cardiorespiratory arrest. As such, it is important to try and obtain cross-sectional imaging to determine the extent of airway compression prior to any intubation attempt.
A number of signs and imaging features suggest a higher risk of impending cardiorespiratory compromise, though some presentations can be quite subtle.
What are some considerations for transport and management?
Imaging is important – it helps establish a diagnosis and plan interventions, including intubation. However, lying flat for the scan may exacerbate the compression and worsen cardiac and respiratory complications.
Positioning the child either lateral or prone can mitigate some of the effects of gravity. The child might let you know about a favoured position which provides symptomatic relief. Don’t ignore them! An anaesthetist should be present for the scan.
Although CT is the gold standard imaging modality, the child may be too unstable. If this is the case, an erect AP and lateral CXR can help establish the size and location of the mass. Ultrasound can be used to identify any large pleural effusions.
The priority is to maintain airway tone and spontaneous ventilation. If intubation really cannot be avoided, don’t give a neuromuscular blocker, and use a spontaneous ventilation technique.
If ventilation becomes compromised try to reverse the airway compression – change the child’s position, increase the oxygen flow rate, and use CPAP to splint the airways. ENT may also need to be involved – a rigid bronchoscope may bypass the obstruction and can be used to railroad a tracheal tube past it.
Where you place a cannula matters too. Upper limb veins drain into the superior vena cava, but a mediastinal mass may compress the SVC. Use lower limbs veins for cannulas.
Some have suggested pre-emptive ECMO for high-risk patients. This is often not feasible in kids who would not tolerate the procedure without significant sedation (have you seen the size of those lines!). There is, however, a role for rescue ECMO. One final option is emergent transfer, prior to intubation, to a centre that has ECMO on standby. It’s worth discussing this with your retrieval service.
Children who have a malignant tumour may require chemotherapy or radiotherapy, though, significant destruction of tumour cells may cause tumour lysis syndrome and complicate diagnosis – this management should be guided by the oncology team.
Management must be multidisciplinary involving anaesthetics, paediatric retrieval service/paediatric intensive care, ENT and oncology teams (as well as the cardiothoracic surgery team – not always available).
Five-year-old Ginny presents to the Emergency Department with a syncopal episode. She has been treated for a viral-induced wheeze over the last three weeks, but her parents tell you that the inhalers do not make any difference.
When put the sats probe, on you notice that both of her hands are a bit swollen and that she begins to desaturate when lying flat.
A CXR demonstrates a mediastinal mass.
You contact ICU, anaesthetics, ENT, and oncology with a plan to attempt more definitive imaging in the prone position (which Ginny tells you is much comfier)
What’s the evidence for our emergent management?
The evidence related to mediastinal masses in children is largely based on case reports, expert consensus opinions, and observational imaging studies. Arguably, more robust research is neither feasible nor ethical to conduct in such a rare and time-critical emergency. However, small observational studies have helped to describe the initial presentation and factors associated with the development of acute airway compromise.
One such case series analysis looked at 29 consecutive children presenting to the Women’s and Children’s Hospital in Singapore. Case notes were analysed to look for patterns in presentation as well as factors associated with acute airway compromise in children with mediastinal masses. The median age at diagnosis was 47 months (range 1-173 months).
Nearly a quarter (24.1%) of the patients studied were asymptomatic at presentation, supporting previous reports that up to one-third of childhood mediastinal masses are incidental findings. 8/29 patients (27.6%) presented with airway compromise, with 5 of those 8 (62.5%) masses located in the anterior mediastinum. The anterior location of the mass was identified as one of the main risk factors for developing acute airway compromise (P=0.019). 11/29 (37.9%) patients had airway compression or displacement by mediastinal mass on chest x-ray. Histologically, lymphoma was significantly associated with an increased likelihood of airway compromise. Neurogenic tumours were less likely to be associated with airway collapse.
Age, gender and race were considered but held no significance. It is worth noting that the study patients were relatively young – neurogenic masses were the most common in their cohort. Lymphomas are more common in adolescents. The main drawback of the series is the small sample size, limiting the wider applicability of the author’s conclusions. Given that the study is now nearly 20 years old, newer research is needed to further back up current guidelines.
Take-homes
– Mediastinal masses can cause life-threatening airway and cardiovascular compression.
– There are several high-risk signs; however, some masses are asymptomatic.
– Simple tests (e.g. CXR) may be enough to make a preliminary diagnosis.
– CT imaging can help characterize a lesion but is not without risks due to positioning. Consider lying the child lateral or prone.
– Anaesthesia/sedation may reduce airway tone and worsen compression!
– When anaesthesia is necessary, avoid neuromuscular blockers and consider using spontaneous ventilation or CPAP.
– When anaesthesia is necessary, avoid neuromuscular blockers and consider using spontaneous ventilation or CPAP.
About PICSTAR
PICSTAR is a trainee-led research network open to all doctors, nurses and allied health trainees within Paediatric Intensive Care. We are the trainee arm of the Paediatric Critical Care Society – Study Group (PCCS-SG) and work with them on research, audit and service evaluation.
If you would like to join PICSTAR and get involved in projects, have ideas you would like to propose or get advice/mentorship via PCCS-SG, don’t hesitate to contact us at picstar.network@gmail.com. See their website for more: https://pccsociety.uk/research/picstar/
References
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McLeod M, Dobbie M. Anterior mediastinal masses in children. BJA Educ. 2019;19(1):2126.doi:10.1016/j.bjae.2018.10.001
Rijal A, Shrestha A, Chaudhary S, Shrestha A. Superior vena cava syndrome in a child with mediastinal mass: A case report. Clin Case Reports. 2022;10(11):1-4. doi:10.1002/ccr3.6647
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