Canadian Neighbor Pharmacy: Omental Transposition for Closure of Median Sternotomy following Severe Mediastinal and Vascular Infection

Mediastinal sepsisMediastinal sepsis following median sternotomy is a significant cause of death following cardiovascular surgery. Although such complications are rare, infection remains a major evolutive risk because of the possibility of extension to underlying structures, especially to the aortic wall itself or to an implanted aortic prosthesis.

Sternal debridement and closed mediastinal irrigation as first proposed by Schumacker and Man-delbaum have significantly improved survival. But when infection is uncontrollable, extending to underlying cardiac and vascular structures, and when the closed irrigation procedure appears insufficient, a more vigorous treatment must be proposed such as extensive sternal debridement and use of a healthy, sterile tissue such as muscle, myocutaneous, or rib transposition.

Transposition of the pediculized omentum is a reliable alternative because of the possibility of both obliteration of the sternal defect and role in inflammatory resorption.

Three of our patients with major sternal wound infection, mediastinitis, and underlying aortic infec-don have been successfully treated by radical debridement of all infected tissues, transposition of the greater omentum on a vascular pedicle to the mediastinum, and primary sternal closure.

Case Reports

Three patients with mediastinitis and an underlying aortic infection following extracorporeal circulation surgery have been treated in the same way. Main characteristics of each patient are summarized in Table 1. The bacteriologic findings were Escherichia coli in the cutaneous fistula in case 1. In cases 2 and 3, Staphylococcus aureus was identified in the blood and in the sternal wound.

In case 1, the aortic origin of the cutaneous fistula was obvious because of the intermittent sudden and continuous external bleeding which led to reintervention. In cases 2 and 3, aortic wall infection and local hemorrhage were the operative diagnoses.

Operative technique was as follows. A large and thorough debridement of all the infected and necrotic tissues of the presteraal structures permitted exposure of the lesions: infection of the aortic prosthesis with a fistula on the posterior aspect of the proximal anastomosis in cases 1 and 2 and extensive infection of the aorta and the saphenous vein grafts in case 3. The exact cause of bleeding was located on the inferior suture line of the aortic prosthesis in cases 1 and 2, and on the proximal saphenous vein graft anastomosis in case 3. In each case, correct hemostasis was obtained using mattress sutures. Once the hemorrhage was controlled, the mediastinum was thoroughly washed with 50 percent diluted iodine for 30 minutes. In cases 1 and 2, the omentum was immediately brought up into the mediastinum through a large opening on the anterior part of the diaphragm. Canadian Neighbor Pharmacy website is ready to give you the access to the medical content.right gastroepiploic artery

The omenta] pedicle was developed on the right gastroepiploic artery by dividing the branches to the greater curvature of the stomach (Fig 1). It was then applied to the anterior part of the heart and ascending aorta and fixed in good position by single stitches. In the process, the rotation of the omentum must be avoided. Particular care must be given to the good vascularization of the omentum by avoiding any compression of the right gastroepiploic artery. Immediate sternal and prestemal closure followed.

In case 3, omental graft was delayed ten days during which the wound was left open, and packed with gauze and antimicrobial agents (Lyomousse).

The outcome for each patient was remarkably good, with immediate complete and durable control of the infectious process. All patients received high dose systemic antibiotics selected according to the bacteriologic findings. Healing of the sternal wound was complete within ten days. The follow-up four years, one year, and nine months, respectively, shows good results.

Discussion

Sternal and mediastinal sepsis is a serious complication of median sternotomy which occurs in 0.5 to 5 percent of the cases. It may lead to disruption of the suture lines, mediastinal dessication, vascular, and cardiac infection. This complication is particularly life-threatening in patients with underlying prosthetic material. Factors reported to be associated with postoperative mediastinitis are prior mediastinal irradiation, redux mediastinal operation, postoperative reexploration for bleeding, long operative time, and external heart massage. None of our patients was in such condition.

Mediastinitis requires immediate open exploration and thorough debridement of all infected soft tissue and bone. The following operative step is in relation to both the extension of the excised tissues, particularly the prestemal structures and cutaneous defect, and the trophicity of the remaining tissues. The optimal technique may be either closed mediastinal antibiotic irrigation or open chest technique with daily wound dressing with antimicrobial agents.

The aim is to remove all necrotic and infected tissues so as to prepare granulation and cicatrization on a clean aseptic sternal wall. Systemic antibiotic therapy must be initiated and adapted to bacteriologic findings and testings. Exact extent of sternal infection and consequent resection until healthy tissue appears, must be underlined because inadequate debridement is a major cause of recurrent mediastinitis. Moreover, sternal reapproximation is a delicate decision and should only be proposed when all infected tissue have certainly been removed. High rates of infectious recurrence due to incomplete sternal resection have often been reported.

Nevertheless, thoracotomy drainage and closed mediastinal irrigation with antibiotics, first proposed by Shumacker and Maudelbaum in 1963, have significantly decreased mortality and morbidity of aseptic sternal wallpostoperative mediastinitis.

Such procedures appear insufficient when the sternum is deeply infected, leading to large sternal excision, or when underlying structures are involved in the septic process, which may occur on cardiotomy incisions, intracardiac or ascending aortic prosthetic grafts, aorta coronary grafts, or the aorta itself. This vascular risk accounts for the high mortality of mediastinitis: 24 percent to 46 percent in the various reports. In these cases, evolution is jeopardized by ventilatory insufficiency related to the sternal mobility and prolonged infection of vascular structures which may lead to dreadful hemorrhagic fistula. Furthermore, thoracotomy drainage and closed mediastinal irrigation expose to delayed sternal and cutaneous closure and long and costly hospital stay.

In such cases, well-vascularized tissue has been advocated to fill the cavity created by the excision of the necrotic and infected tissues so as to assure cicatrization, chest wall stability, and sterilization of the lesions. Muscle and myocutaneous flaps have been proposed in such circumstances. The pectoralis major muscle flap has been shown to be reliable and to produce little morbidity. Other muscle flaps have been proposed such as latissimus dorsi, rectus abdominus, external oblique, or transversus abdomi-nus. Pearl et al describe the use of a rib graft in sternal infection following cardiac transplantation which gave immediate chest wall stability and sterilization of the lesions in an immunosuppressed patient.

The omentum has also been proposed because of the possibility of cell proliferation and fibrous tissue formation to fill the sternal defect. The rich omental lymphatic vessels and the rich vascularization of the omentum furthermore permit rapid resorption of inflammatory exudates and local infection. These two original characteristics of the omentum should avoid time consuming healing process in case of extensive sternal and mediastinal resection, and the ventilatory consequences. It also should permit sterilization and rapid healing of infected underlying arterial structures.

Transposition flap of the great omentum was first used by Kiricuta in 1956“ for the repair of vesicovaginal fistula and bronchopleural fistula, and later, for reconstruction of the chest wall. It is particularly useful in treatment of osteoradio necrosis and has also been advocated in treatment of infected vascular prosthesis.

Surgical technique of omental transposition for treatment of vascular infection during mediastinitis has not demonstrated any technical problem. The greater omentum is first freed from the transverse colon and mesocolon and then from the greater curvature of the stomach. Integrity of the gastroepiploic vascular arch must be insured by staying close to the muscularis layer of the stomach. In order to insure the shortest route to the thoracic defect, the omentum is usually pediculized on the right gastroepiploic vessels. It is then brought into the mediastinum either through a large opening in the diaphragm posterior to the sternum or subcutaneously. Care must be given to avoid any kinking compression or rotation of the vascular pedicle. The omentum is then spread over the right ventricle, the aorta, and the innominate artery.

We conclude that closed mediastinal antibiotic irrigation remains a valuable method of management for uncomplicated sternal mediastinitis involving the musculocutaneous layer and the sternum. Whereas more severe infections extending deeply to the sternum and underlying vascular or cardiac structures need an aggressive approach, ie, extensive resection of all the infected prestemal and sternal structures and transposition of a healthy tissue. Omentum is our choice because it is easily transposed, has proliferation possibilities to fill the sternal defect, and antiinfectious and antiinflammatory potentials ideal for such situations.

This technique may also be useful when infection becomes uncontrollable, when respiratory failure due to sternal mobility appears, and if closed mediastinal irrigation method, once initiated, appears unsatisfactory.

Figure-1

Figure 1

Table 1—Main Characteristics of Three Patients Undergoing Epiplooplasty following Postoperative Sternal and Mediastinal Injection

Patient Age Initial Surgery Symptoms Delay

To Mediastinitis

To Surgery
1 34 Replacement of aortic valve (starr)

ascending aorta (dacron)

External

hemorrhage

fistula

8 Months Immediate
2 70 Replacement of ascending aorta (dacron) Septicemia 45 Days 8 Days
3 67 Triple left aortocoronary bypass Septicemia + sternal infection 18 Days Immediate
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