Acute mediastinal bleeding during vacuum‐assisted closure

Abstract

Vacuum‐assisted closure is commonly used to treat post‐sternotomy mediastinitis. Several studies show improved outcome using vacuum‐assisted therapy; however, risks using negative pressure should not be underestimated. We describe two cases of acute mediastinal bleeding during vacuum treatment for post‐sternotomy mediastinitis and discuss preventative measurements.

Introduction

Post‐sternotomy mediastinitis is a rare but devastating complication of open heart surgery. In the last decades many techniques have been used to treat this infection. Vacuum‐assisted closure (VAC) is commonly used as therapy, stimulating wound granulation and stabilizing the sternum using negative pressure. This technique was first described by Davydov et al. and has proven his success over the last years 1, 2, 3. Besides positive results of VAC in the treatment of post‐sternotomy mediastinitis, adverse events are also reported 4, 5. We describe two cases of acute mediastinal bleeding due to VAC and discuss preventative measurements which could be taken during VAC treatment.

Case report 1

A 57‐year‐old Caucasian male was admitted to our department for cardiac revascularisation. The patient had a medical history with chronic obstructive pulmonary disease (COPD) gold I. He received three distal anastomoses; to the left anterior descending artery, to the obtuse marginal branch and the posterior descending artery, for which the left and right internal thoracic arteries were used with a Y‐graft anastomosis. Postoperatively the sternum remained unstable for which 3 days later a sternal refixation was performed as described by Robicsek et al. (6). Antibiotics were given previous to the operation and tissue cultures remained negative. Patient presented himself on the emergency department 1 week after discharge with a superficial wound infection and a dehiscent sternum. Under suspicion of post‐sternotomy mediastinitis an operation was performed on the same day. Extensive debridement was performed and the wound remained open. VAC therapy™ (KCI, Houten, The Netherlands) was started 1 day postoperatively. A tailored polyvinyl alcohol dressing was fitted substernal to protect vital structures. A second polyurethane sponge was placed between the sternal edges and the subcutaneous layers. VAC therapy was initiated with a negative pressure of 125 mmHg. Coagulase‐negative Staphylococcus was cultured from the tissue and antibiotic treatment with Cefuroxime and Vancomycin was initiated for the duration of 9 weeks. After 10 days, an acute bulging of the VAC was witnessed due to mediastinal bleeding. Sponges were carefully removed in the operating theatre and the origin of the bleeding was localized in the right atrium. Bleeding could be stopped using floseal® (Baxter, Deerfield, IL). Mediastinitis was further managed with open packing. Unless this treatment a spontaneous right ventricular bleeding occurred three weeks later. This defect in the right ventricle was closed with a pericardial patch. The sternum could be closed using an omental plasty and osteosynthetic materials 2 weeks later. Redon drains were used temporarily draining the mediastinum. Patient was discharged home after a hospital stay of 62 days.

Case report 2

A 58‐year‐old Hindustani male was admitted to our hospital for cardiac revascularisation. Patient had an extensive medical history including hypertension, non insulin dependent diabetes mellitus, renal failure, COPD gold II, previous cardiac surgery and adenocarcinoma for which a lobectomy of the right upper lobe was performed. He received three venous anastomoses; on the left anterior descending artery, the obtuse marginal branch and the posterolateral branch of the right coronary artery. Mediastinitis was diagnosed with a strain of Pseudomonas in the tissue cultures 1 week after surgery. Sternal débridement was performed and VAC therapy™ (KCI) was initiated. A polyvinyl alcohol dressing was placed over the viable structures to protect them from the negative pressure. Ceftazidime was given for 6 weeks. After 19 days of VAC therapy, a massive bleeding occurred under the VAC system. An emergency operation was performed. A bleeding of the proximal anastomosis was seen which could be sutured with a few stitches. A second mediastinal bleeding occurred 3 weeks later. Again this bleeding was caused by disruption of the proximal anastomosis. At this moment, the anastomosis could not be salvaged. Eleven days later, the mediastinum could be closed using a pectoral muscle flap interposition, hereafter patient recovered well. He was discharged home in a good condition after a total length of stay in the hospital of 90 days.

Discussion

During the last decade VAC has become a popular treatment for post‐sternotomy mediastinitis, reducing mortality rates compared to conventional treatment modalities (7). The use of negative pressure has been proven to stimulate wound healing but comes with risks. Several authors have pointed out the importance of covering the viable tissues like the right ventricle and the bypass grafts with paraffin gauzes or other protective material. We show that even when viable tissue is carefully covered with polyvinyl alcohol dressings the risk of acute mediastinal bleeding still exists. By using high negative pressure, the VAC system stabilises the sternum. This property is important in patients with chronic pulmonary diseases like in our cases because of frequently heavy coughing. Malmsjöet al. described that the negative pressure of the VAC system causes the heart to displace towards the sharp edges of the sternum which could cause rupture of the right ventricle (8). The coughing of patients with chronic pulmonary disease causes additional friction of the heart against the sternal edges. We believe for that reason that when high negative pressure is used to stabilise the sternum in patients with chronic pulmonary disease, extra care has to be taken covering viable tissue by several layers of protective material. This material should not only be placed under the vacuum sponges, but also under the edges of the sternum to protect the heart from the sharp edges (Figure 1).

Figure 1.

A protective sponge is placed over the heart and under the sternal edges, to protect the heart from the sharp edges of the sternum.

To be able to place adequate protection for the viable tissue, one has to make sure that the right ventricle is entirely freed from the sternum. This is especially important in patients who are previously operated via median sternotomy because of presence of severe adhesions. When massive bleeding occurs under the VAC system, the negative pressure delivery unit should be turned of immediately, preventing extreme blood loss. Patients should be taken to an operating theatre to find the source of the bleeding and repair the defect.

Conclusions

VAC therapy has proven its success in the treatment of post‐sternotomy mediastinitis; however, one should be aware of severe complications caused by negative pressure. Adequate protection of the viable tissue is a necessary preventive measure which should be performed with the utmost care, particularly in patients previously operated or with chronic pulmonary disease.