Superior vena cava syndrome pediatric considerations
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
SVCS refers to the symptoms associated with the compression or obstruction of the SVC; the compression of the trachea is termed superior mediastinal syndrome (SMS). Because SMS and the resulting respiratory compromise frequently occur in children with SVCS, the two syndromes have become almost synonymous in pediatric practice. In adults, the trachea and the right mainstem bronchus are relatively rigid structures compared with the vena cava, but in children these structures are more susceptible to compression. In addition, the relatively smaller intraluminal diameters of a child’s trachea and bronchus can tolerate little edema before respiratory symptoms occur. Because of this accompanying respiratory component, SVCS in children differs from the adult syndrome and constitutes a serious medical emergency.
Causes
- SVCS is rare in children and appears at presentation in 12% of pediatric patients with malignant mediastinal tumors.
- Whereas the most frequent cause of SVCS in adults is bronchogenic carcinoma, in children the most frequent malignant cause of the syndrome is non-Hodgkin lymphoma.
- As in adults, a frequent nonmalignant cause is thrombosis from catheterization for venous access.
Diagnosis
A physical examination, chest radiography, and the medical history of the patient are usually sufficient to establish a diagnosis of SVCS.
Symptoms
The most common symptoms of SVCS in children are similar to those in adults and include:
Symptoms that are less common but more serious are:
Biopsy
If lymphoma or other malignant disease is suspected, it is desirable to obtain a tissue sample for diagnosis. However, the procedure to obtain the specimen may involve significant risk and may not be clinically feasible. Children with SVCS have a poor tolerance for the necessary general anesthesia because the accompanying cardiovascular and pulmonary changes aggravate the SVCS, often making intubation impossible. Also, extubation may be difficult or impossible, thus requiring prolonged airway provision (intubation).
CT
A CT scan of the chest to determine tracheal size and a flow volume loop may help evaluate anesthetic risk. Because anesthesia use is a serious risk, the diagnosis should be made with the least invasive means possible. Published reports suggest a stepwise approach to diagnosis.
Echocardiography
Upright and supine echocardiography may help evaluate anesthetic risk.
Treatment
Medical Therapy
When a malignant mass is the cause of the SVCS, the situation may be a medical emergency with no opportunity to establish a tissue diagnosis. In these cases, the most appropriate course may be to initiate empiric therapy prior to biopsy. The traditional empiric therapy is irradiation, with the daily dose governed by the presumed radiosensitivity of the tumor. After irradiation, respiratory deterioration from the apparent tracheal swelling may occur because of the inability of narrow lumens in children to accommodate edema and because of the greater degree of edema at onset, which is due to the rapid speed at which tumors grow in children. In these situations, a course of prednisone at 10 mg/m2 of body surface area 4 times per day may be necessary.
In addition to radiation, empiric therapy of SVCS has included chemotherapeutic agents incorporating steroids, cyclophosphamide, or both in combination with an anthracycline and vincristine. If the tumor fails to respond, it may be a benign lesion.
Surgery
If surgery becomes necessary, it should be performed with the patient in the semi-Fowler’s position, allowing the surgeon the ability to rapidly change the patient's position to lateral or prone. Cardiopulmonary bypass facilities and a rigid bronchoscope should be available in a standby capacity.