Anaesthetic management of a child with massive extracranial arteriovenous malformation.

Vascular tumors affect the head and neck commonly but arteriovenous malformations are rare. Vascular malformations are often present at birth and grow with the patient, usually only becoming significant later in childhood. Embolization has been the mainstay of treatment in massive and complex arteriovenous malformations. We present a case of massive extracranial arteriovenous malformation in a 7-year-old boy causing significant workload on right heart and respiratory distress. The management of angioembolization under general anaesthesia and anaesthetic concerns are presented.

Introduction

Neck masses in children are more commonly inflammatory than congenital or developmental.[1] Vascular anomalies, commonly vascular tumors or vascular malformations, are usually developmental in origin and can present as a neck mass. Vascular malformations can be arterial, venous, lymphatic, or a combination of these.[1]

Complex arteriovenous malformations (AVMs) in the neck, due to their anatomical location, may present with pressure symptoms, particularly on airway, and circulatory problems. They pose multiple challenges to the anaesthesiologist, most importantly airway collapse and heart failure.[2] Embolization alone has been the mainstay of treatment in these types of malformations; however, in some cases, surgery may be an option. Owing to the rare nature of this medical condition, there is hardly any literature describing the anaesthetic management of patients with massive AVM in the neck.

Case Report

A 7-year-old boy presented to the pediatric surgery clinic with a 6-year history of enlarging neck swelling. On clinical examination, a large nontender mass was present in front of the neck extending laterally to the right sideand the back, covering the entire right side of the neck [Figure 1]. There was skin plethora at neck, shoulder, and upper part of chest along with a swollen right arm [Figure 2]. This swelling had appeared at 6 months of age and had gradually increased with time. Excisional biopsy was done at 3 years of age and a diagnosis of lymphangioma was made, for which he had received two sets of sclerotherapy.

Figure 1

Large mass covering whole right side of neck

Figure 2

Swollen right arm with skin plethora

A differential diagnosis of AVM and enlarged lymph node was made and the patient was advised computed tomography (CT) angiogram, which showed a large cervical AVM with predominant supply from right subclavian and vertebral arteries [Figure 3]. The treatment options were discussed with parents and angioembolization was planned under general anaesthesia.

Figure 3

CT angiogram showing massive AVM

In preanaesthesia evaluation, child had difficulty in breathing aggravated in supine position, cough, and headache. There was pitting edema of lower limbs up to ankles. The arterial pulses in the right upper limb were weaker than those on the left side. A palpable thrill and continuous machinery murmur was heard in right supraclavicular region. Fine crackles were heard bilaterally over the lung bases which were consistent with a diagnosis of heart failure. The airway was Mallampati class III and neck movements (flexion and extension) were mildly restricted.

All laboratory investigations were within normal limits except for hypokalemia (serum potassium 2.9 mEq/L), which was probably secondary to chronic frusemide therapy. Child was treated with intravenous 4 mEq/h potassium chloride supplementation for 24 h. Chest radiograph showed a widened mediastinum, prominent superior vena cava shadow, and tracheal shift to the left. Electrocardiography revealed sinus tachycardia and evidence of left ventricular hypertrophy (LVH). Two-dimensional echocardiography showed mild dilatation of all cardiac chambers, mild LVH, and mild biventricular systolic dysfunction with increased flow velocities across all cardiac chambers. The echocardiographic features were suggestive of high-output cardiac failure. The child was managed with oral digoxin 5 mcg/kg q12hrly and intravenous frusemide 1 mg/kg q12hrly. After stabilization of heart failure, the angioembolization was scheduled. Equipment for difficult airway management, resuscitation drugs, and help was specially arranged for the radiology suite. Two units of packed red cells were also arranged.

The child was placed in propped up (45°) position. A peripheral intravenous catheter (18 G) was inserted. After application of routine monitors including electrocardiography, pulse-oximetry, end-tidal CO2, and noninvasive blood pressure, patient was preoxygenated for 5 minutes. Inhalational induction of anesthesia was done with sevoflurane. After ensuring adequate mask ventilation, succinylcholine 30 mg was given, and trachea intubated with a 5.5 mm ID cuffed endotracheal tube in the propped up position. Fentanyl 2 mcg/kg was administered intravenously for analgesia. Local anesthetic (lignocaine 1%) 5 ml was injected over the femoral area. Invasive arterial pressure monitoring was done using the sidearm port of femoral sheath as the child had a swollen right arm and both the femoral areas were required by radiologist. anaesthesia was maintained with Isoflurane 1.5–2% in 50:50 oxygen and air. A Foley's urinary catheter was inserted to monitor hourly urine output. Embolization of the AVM with isobutyl-2-cyanoacrylate (IBCA) glue and vaso-occlusive coils was done in a three hour procedure. During the procedure some IBCA glue, used to occlude the feeding vessels, leaked into the pulmonary circulation. Due to anticipated development of pulmonary hypertension (a known effect of IBCA) and worsening of cardiac failure, it was decided to electively ventilate the patient postprocedure.

In the intensive care unit (ICU), the chest radiograph showed tiny numerous high density materials in both lung fields especially in basal segments [Figure 4]. Echocardiography revealed severe tricuspid regurgitation, severe pulmonary hypertension, and dilated right heart. He was started on sildenafil citrate (a pulmonary vasodilator) 2 mg/kg q6hrly and it was given through nasogastric tube, which causes marked improvement in symptoms. The child's trachea was successfully extubated after 48 h and he was shifted to the special care unit where he remained hemodynamically stable. The child was discharged from hospital after three days.

Figure 4

Chest X-ray showing deposition of high-density material

Discussion

AVMs are high-flow vascular anomalies with multiple, low-resistance shunts which short-circuit the capillary bed.[3] They can be congenital or acquired. Acquired AVMs can develop after catheterization procedures, surgery, trauma, or the rupture of aneurysms. Congenital AVMs outside the nervous system are relatively uncommon and their usual sites are neck, extremities, liver, heart, and thoracic wall.[4]

The clinical features of an extracranial AVM can vary according to the site, size, and nature of the vascular defect. Patients may present with asymptomatic swellings or cosmetic defects with a palpable pulsatile mass, bounding pulses, wide pulse pressure, a continuous murmur and/or thrill over the site, and Nicoladoni-Branham's sign (decrease in heart rate and increase in systemic blood pressure when the arteriovenous fistula is compressed). A large AVM, with a significant shunt, causes chronic volume overload of the heart that leads to remodeling, ventricular dilatation, and heart failure. Patients need optimization with diuretics and chronotropic drugs. Wong et al. reported a case of congenital AVM in thoracic region that caused heart failure.[5]

Treatment of massive extracranial lesions is difficult. Embolization is the principle treatment modality and the therapeutic strategy may consist of selective embolization in combination with surgical ablation and reconstruction.[6] Occlusive agents used in AVM embolization include detachable thrombosing coils, permanent balloons, sclerosing agents, quick-acting glues, and particulate materials.[7] Passage of the particulate material into the systemic or pulmonary circulation may complicate the procedure. Pulmonary embolism may result from the particulate material, especially during embolization of massive AVM lesions containing large fistulae.[7] Of these occlusive materials, the cyanoacrylates need important considerations. The IBCA glue is liquid polymerization agent, which is injected into the nidus of the AVM. Various complications, usually related to the central nervous system, have been described resulting from this therapy. Asymptomatic embolization of IBCA to the lungs has been described.[8] Goldman et al.[9] describe a 12-year-old girl, for IBCA–ethiodized oil embolization of a large nasopharyngeal AVM, who developed respiratory difficulties about 31/2 h after the procedure. The chest X-ray showed high-density glue and patchy pulmonary consolidations in both lungs, and the patient died of a respiratory arrest.

Sildenafil is a selective inhibitor of phosphodiesterase type 5 (PDE5). Present throughout the body, PDE5 is found in high concentrations in the lungs.[10] Inhibition of PDE5 enhances the vasodilatory effects of nitric oxide in pulmonary hypertension by preventing the degradation of cyclic guanosine monophosphate (cGMP), which promotes relaxation of vascular smooth muscle and increases blood flow. In animal models and human trials, sildenafil has been found to produce a relatively selective reduction in pulmonary artery pressure without adverse systemic hemodynamic effects. Oral sildenafil received approval for treatment of pulmonary hypertension (PH) after a double-blind, placebo-controlled trial showed it to be an effective treatment of chronic PH in adults.[10] Based on case reports and studies conducted with sildenafil to date, an initial dose of 0.25–0.5 mg/kg given orally every 4–8 h, as recommended for pediatric patients with pulmonary hypertension.

Knowledge of the risks and hazards of the procedure and collaboration with specialists, including neuroradiologists, critical care physicians, and potentially neurosurgeons, ultimately form the basis for appropriate management.[2] The goals of anaesthesia are protection of the airway, maintaining cardiovascular and neurological stability, manipulating systemic and regional blood flow, and managing anticoagulation.[3] In a radiological suite, peripheral location considerations involving equipment, monitors, and appropriate drugs and sustaining the patient's immobility during the radiological procedures, while managing potential perioperative complications are essential.[3] At our institution, the difficult airway cart is called from main operating room and this is the normal practice when anticipated difficult airway presented in radiology. In selected cases, an ICU bed should be arranged and sedatives/anxiolytics avoided as premedication.

There are some cases, such as embolization of extracranial vascular malformations that drain into the intracranial venous system, induced hypercapnia may be needed. Induction of hypercapnia promotes high venous outflow from the cerebral venous system and help minimize the risk for inadvertent movement of embolic material into the intracranial compartment.[11] The disadvantage of induced hypercapnia is systemic hypertension which increases afterload and can worsen the heart failure. We maintained normocapnia in our patient to avoid deleterious effects of induced hypercapnia.

In conclusion, massive AVM arising in neck is a rare presentation. Awareness of its various implications and their management helps achieve the best possible outcomes.