Surgicel Packing and an Erroneous Diagnosis of Mediastinitis in a Neonate

Abstract

Internal accumulation of the topical hemostatic agent Surgicel® can mimic fluid collections that might be misdiagnosed as an abscess or a hematoma upon 3 common postoperative imaging methods. Herein, we report the unusual case of a neonate who underwent surgical repair of complex congenital heart conditions and then required early re-exploration, prompted by initial suspicion of mediastinitis on the basis of computed tomographic findings. During reoperation, it was determined that the mass on computed tomography was an accumulation of oxidized Surgicel. We discuss the capabilities and limitations of various imaging methods in the achievement of an accurate differential diagnosis.

Surgicel® (Ethicon, Inc., a Johnson & Johnson company; Somerville, NJ) is an absorbable, cellulose-based material. It has proved useful in the control of bleeding that originates from delicate or friable tissues. On conventional radiography, ultrasonography, and computed tomography (CT), it is difficult to differentiate between an abscess and packed Surgicel.

Here, we report an unusual case of a newborn who underwent initial correction of congenital heart defects and reoperation 22 days later for suspected mediastinitis. We describe the unanticipated results of the re-exploration.

Case Report

In April 2008, a 12-day-old male neonate (weight, 3.65 kg) was admitted to our pediatric intensive care unit because of breathing discomfort, labial cyanosis, and a holo-systolic murmur. Transthoracic echocardiography revealed a type C interrupted aortic arch, an 8-mm perimembranous ventricular septal defect, and a 5-mm ostium secundum atrial septal defect. The descending aorta originated from a 3.8-mm arterial duct. The systolic pressure in the pulmonary artery was calculated at 62 mmHg.

Elective correction was performed 6 days later, via median sternotomy. The thymus was absent, and a type C interrupted aortic arch was confirmed. The diameter of the ascending aorta was 7 mm, and the anterosuperior pulmonary trunk was aneurysmal (diameter, 21 mm). The aberrant right subclavian artery originated from the descending aorta, immediately distal to the left subclavian artery. Bypass was performed with dual arterial perfusion and double-vein cannulation. Aortic reconstruction was carried out during 30 min of selective right carotid perfusion. The arterial duct was transected. The aortic stump was cross-clamped, trimmed of all remaining ductal tissue, and anastomosed end-to-side to the left side of the ascending aorta. During rewarming, the ventricular septal defect was closed with a bovine pericardium patch, through a right atriotomy. After protamine was administered, persistent bleeding from the dissected mediastinal tissue was controlled with Surgicel packing. The thorax was left open and protected with a transparent plastic patch. Chest-tube drainage (4.8 mL/kg/hr in the first 12 hr) was treated with one 10 mL/kg transfusion each of red blood cells and platelet concentrate.

The chest was closed in the intensive care unit on the 2nd postoperative day. The procedure was performed by an attending surgeon who had not participated in the previous operation. He found black-stained Surgicel material between the distal ascending aorta, the right atrial appendage, and the pulmonary trunk, and decided, for safety reasons, not to remove it.

The patient's condition improved until the 6th postoperative day, when pneumonia was suspected due to fever, leukocytosis was evident due to a shift to the left in white-blood-cell count, and pulmonary opacity was seen on a thoracic radiograph. Antibiotic therapy with vancomycin and amikacin was initiated.

On the 15th postoperative day, a yellowish secretion was noticed at the lowest third of the surgical incision. A CT scan of the chest revealed a 2.6 × 0.8-cm cystic hypodense mediastinal mass that encircled the distal ascending aorta and was limited laterally by the superior vena cava. This finding was interpreted as a fluid collection that was consistent with mediastinitis or hematoma (Fig. 1A). Because no microorganism could be isolated from the postsurgical secretion and the patient was by now afebrile and thriving, conservative treatment was maintained.

Fig. 1 Computed tomographic scans of the chest on the A) 15th and B) 22nd postoperative days. A 2.6 × 0.8-cm hypodense mediastinal collection encircles the distal ascending aorta. In the earlier image, an artifact was generated by a superior vena cava catheter.

Although the surgical incision appeared to be healing well, the patient developed sepsis on the 22nd postoperative day. The results of a new chest CT scan (which was almost unaltered in comparison with the earlier scan) raised suspicion of contained mediastinitis (Fig. 1B), and the patient underwent reoperation. Contrary to expectation, only a blackened Surgicel mass was found. The mass was contained laterally by the superior vena cava and anteriorly by the right atrial appendage, and it was densely packed between the distal ascending aorta, neoaortic arch, and pulmonary trunk. The material adhered weakly to the surrounding tissues, and it was easily removed. Histopathologic examination of the excised mass revealed no growth of microorganisms. The patient did well postoperatively and was discharged from the hospital 7 days later. He remains in follow-up with no impairment related to the reported event.

Discussion

Surgicel is an absorbable, cellulose-based material that has proved useful in the control of bleeding that originates from delicate or friable tissues. It is believed that contact between blood and the oxidized cellulose mass can lead to platelet adhesion, blood clotting, and local thrombosis, with consequent hemorrhage cessation.^1,2

The reabsorption of Surgicel depends on the amount of the material that is used in the procedure and on the blood flow in the neighboring tissues. After a week, the Surgicel mass has been found to be invaded by multinucleated giant cells, which probably contribute to the total elimination of the material 4 to 8 weeks postoperatively.³

If a large amount of Surgicel has been used, its mass can be seen as a radiopaque area on a conventional radiograph.⁴ On ultrasonography, the packed Surgicel may look like a heterogeneous hypodense echogenic mass and may be mistaken for an abscess. The echocardiographic heterogeneity of Surgicel is attributed to its uneven reabsorption rate—faster for its more blood-saturated portions.⁵ Similarly, on CT scan, a Surgicel mass appears as a heterogeneous hypodense mass that is similar to a hematoma or an abscess.⁶

Oto and colleagues⁷ have reported the difficulty of differentiating between an abscess and Surgicel packing—whether by conventional radiography, ultrasonography, or CT—in the recent postoperative period. The authors have highlighted the role of magnetic resonance imaging (MRI) in aiding the differentiation between these entities, in order to avoid unnecessary surgical re-exploration. In the presence of Surgicel packing that has been used for intraoperative hemostasis, the diagnostic uncertainty of the other 3 imaging methods has led to erroneous diagnoses of intra-abdominal abscess after laparotomy⁸ and of brain tumor relapse after neurosurgery.⁴

This uncertainty is also relevant in cardiothoracic surgery. Ibrahim and associates⁹ reported a case of annuloaortic ectasia in which excess Surgicel used for hemostasis was postoperatively mistaken on transesophageal echocardiography for a cystic abscess that was located between the aortic duct and the pulmonary trunk. D'Ancona and colleagues¹⁰ reported meaningful information: although Surgicel packing used during an aortic valve replacement was mistakenly interpreted as a wall hematoma of the ascending aorta on ultrasonography, MRI decisively excluded this diagnosis and correctly identified the Surgicel mass, thus precluding reoperation.

We believe that the persistence of the Surgicel mass in our patient 22 days postoperatively was due to the large amount of the material that was packed into a neonate whose ability to eliminate the Surgicel was probably affected by the complex surgical procedure and prolonged postoperative intensive care. Because we were then unaware of the decisive role of MRI in the distinction between Surgicel packing and abscess, we performed no MRI examination.

The case of our patient suggests that packed Surgicel should be removed upon delayed definitive chest closure and that attending physicians must correctly interpret an apparently small amount of oxidized Surgicel as a possible “tip of the iceberg” of a bulky, concealed mass.