Anaesthetic considerations for children with anterior mediastinal mass are problematic and challenging. This group of children, who may present with little or no symptoms from cardiovascular and respiratory compromise, is at high risk for sudden airway obstruction, cardiovascular collapse and death on the operating table.
We report two children with anterior mediastinal mass who underwent biopsy and venous port insertion under superficial cervical plexus block (SCPB) and dexmedetomidine sedation. Patients’ permission was obtained to publish this case report.
A 10-year-old boy weighing 19 kg presented with a 3-month history of intermittent fever, chills and rigors with a marked reduction in effort tolerance.
On examination, there were multiple cervical and inguinal lymph nodes with gross hepatosplenomegaly. Severe anaemia was present.
His chest radiograph (Fig. 1) showed a large mediastinal mass. The computed tomography (CT) scan revealed a large soft tissue mass within the anterior and middle mediastinum completely encasing the trachea without tracheal compression and also encasing the arch of aorta, left and right pulmonary artery and the superior vena cava. However, these vessels were not compressed.
In view of inconclusive peripheral blood film and fine needle aspiration cytology results, a lymph node biopsy was needed. Under dexmedetomidine sedation, an ultrasound-guided right SCPB was performed. Standard monitors were applied and his respiratory rate and depth of respiration were closely observed. A loading dose of dexmedetomidine 1 μg kg−1 was given intravenously over 10 min followed by a maintenance infusion of 0.5–1 μg kg−1 per h. He was positioned supine for the procedure. With ultrasound guidance and out-of-plane approach, 5 ml of 0.5% levobupivacaine was deposited in the fascial plane just below the midpoint of the posterior border of the sternocleidomastoid muscle using a 24G, 25 mm short-bevel needle (Plexufix, B Braun, Melsungen, Germany).1 After 15 min, the surgeon was able to excise three cervical lymph nodes situated posterior to the sternocleidomastoid muscle.
Biopsy result revealed Hodgkin's disease. For administration of chemotherapy, a subcutaneous venous port was implanted 10 days later under dexmedetomidine sedation, using a similar regime as described above. This enabled the successful performance of a SCPB and port implantation.
In both procedures, performed at separate times, the patient breathed spontaneously with oxygen supplementation via nasal prongs. There was no untoward event in the perioperative period. His respiratory rate was 15–20 min−1. Reduction in blood pressure (BP) and heart rate (HR) was less than 15% from baseline.
A 12-year-old boy weighing 24 kg presented with 3 days history of cough, chest discomfort, facial swelling and distended veins over the chest. There was no history of exertional dyspnoea, difficulty in breathing or stridor.
Chest radiograph showed a huge mediastinal mass. CT scan showed a large heterogeneous mass at the anterior mediastinum encasing the left brachiocephalic vein with superior vena cava compression. The great vessels and the trachea were displaced posteroinferiorly (Fig. 2). Small pleural effusion was also noted bilaterally. Previous biopsy of the mediastinal mass performed under general anaesthesia revealed B-type non-Hodgkin's lymphoma.
He required a subcutaneous venous port for which sedation with a similar dosage of dexmedetomidine was administered, as in case 1. Prior to the ultrasound-guided SCPB, 0.5 mg kg−1 of ketamine was administered intravenously. Supplemental local infiltration was given at the incision site for the port reservoir. Oxygen supplementation was via nasal prongs. The procedure finished uneventfully with minimal reduction in BP and HR.
The clinical application of dexmedetomidine as a sedative agent in children continues to be explored.
Dexmedetomidine has been used as part of a general anaesthetic with placement of laryngeal mask airway in a child with an anterior mediastinal mass.2 The use of dexmedetomidine for sedation has been reported in an adult for anterior mediastinotomy.3
Mediastinal masses can be classified according to anatomic location. Generally, anterior mediastinal mass results in the most severe and critical complications arising from compression of vascular and respiratory structures. Although some children are stable at admission, sudden complications can occur. Their high risk is exacerbated by the smaller airways and reduced cardiorespiratory reserves. Anghelescu et al.4 recommended minimal anaesthetic intervention in patients who present with orthopnoea, upper body oedema, great vessel compression and main stem bronchus compression.
Guidelines for the anaesthetic management of children with anterior mediastinal mass are available.5,6 Diagnostic procedures have been performed under local anaesthesia in adults to avoid the deleterious effects of a general anaesthetic, but this technique may be difficult in children, often making it necessary to choose general anaesthesia. With dexmedetomidine, the maintenance of spontaneous respiration for procedural sedation is clearly a major and desirable advantage in this category of children because this technique would avoid the need for co-operation under local anaesthesia or multiple risks of general anaesthesia (whether with airway control by supraglottic airway device or intubation). The two cases demonstrate that dexmedetomidine can achieve a safe and successful outcome.
Dexmedetomidine has a wide safety margin that includes the production of stable respiratory parameters even though the sedation state of dexmedetomidine is dose dependent and, therefore, at large doses, deep sedation or even general anaesthesia is possible.7 However, dexmedetomidine as a sole agent for more painful procedures such as biopsy, performance of a regional block or insertion of a subcutaneous venous port may not be uniformly effective because of the limited analgesic property. Combining dexmedetomidine and ketamine is suitable for painful procedures, with the latter at a lower dose. As demonstrated in case 2, this enabled the completion of painful procedures without episodes of apnoea, oxygen desaturation and coughing. The sympatholytic and haemodynamic effects of dexmedetomidine (bradycardia, hypotension) are balanced by the sympathomimetic effects of ketamine (tachycardia, hypertension).
Such children are at high risk for morbidity and mortality and deserve meticulous attention, although the procedures are minor in comparison. It cannot be overcautious to state that whatever benefits drugs such as dexmedetomidine may offer as sedation for children with anterior mediastinal mass, a collapsed airway can still occur. Vigilance is necessary. If bleeding occurs, it may be essential to convert to general anaesthetic. In our institution, the cardiothoracic surgeon is on standby for rigid bronchoscopy should airway obstruction occur. Some authors have recommended the immediate availability of cardiopulmonary bypass before induction of anaesthesia.
We suggest that procedural sedation with dexmedetomidine is a promising technique in children with anterior mediastinal mass which meets the goals of minimum anaesthetic intervention with maximum safety.
None of the authors received financial support or have any conflict of interest.
1. Peter Marhofer. Superficial cervical plexus blockade. Ultrasound guidance for nerve blocks – principles and practical implementation
. Oxford: Oxford University Press; 2008. pp. 54–56.
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7. Ebert TJ, Hall JE, Barney JA, et al. The effects of increasing plasma concentrations of dexmedetomidine in humans. Anesthesiology