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Ann Thorac Surg 1998;65:1046-1049
© 1998 The Society of Thoracic Surgeons

Prospective Trial of Catheter Irrigation and Muscle Flaps for Sternal Wound Infection

^a Division of Plastic and Reconstructive Surgery, Department of Surgery, University of Washington School of Medicine, Seattle, Washington, USA
^b Division of Cardiothoracic Surgery, Department of Surgery, University of Washington School of Medicine, Seattle, Washington, USA

Accepted for publication November 6, 1997.

Address reprint requests to Dr Rand, Department of Surgery RF-25, University of Washington, Seattle, WA 98195

	Abstract

Top Abstract Introduction Material and methods Results Comment References

 
Background. Sternal wound infection is a relatively rare but potentially devastating complication of open heart operations. The most common treatments after debridement are rewiring with antibiotic irrigation and muscle flaps. Here we present the results of a prospective trial to determine the appropriate roles of closed-chest catheter irrigation and muscle flap closure for sternotomy infection and to assess the effect of internal mammary artery bypass grafting on the outcome of each treatment modality.

Methods. Between 1990 and 1994, 5,658 sternotomies were performed at the University of Washington Medical Center. Sternal dehiscence occurred in 43 patients, 25 of whom had infection (overall incidence, 0.44%). Because of the infrequency of this complication, a prospective, randomized trial was developed in which the initial approach to sternal dehiscence was rewiring and catheter irrigation. Muscle flaps were used as the primary treatment if the sternum could not be restabilized or as secondary treatment if catheter irrigation failed. Wound resolution, length of hospital stay, and complications were evaluated.

Results. Sterile dehiscences were successfully closed with irrigation in 17 of 18 patients; the other patient required flap closure. Of the 25 patients with infection, 19 had irrigation and 6, closure with flaps primarily. In the group of infected patients, 17 of the 19 who received irrigation also had internal mammary artery bypass grafting. Irrigation failed in 15 (88.2%) of these 17 patients, and salvage was accomplished with muscle flap closure. All 6 patients with infection who were closed primarily with muscle flaps had a successful outcome. Hospitalization averaged 10.2 days when muscle flaps were used primarily and 14.3 additional days for unsuccessful irrigation. When irrigation was successful, the hospital stay averaged 11.2 days.

Conclusions. Catheter irrigation should be reserved for patients without infection or patients with infection but without internal mammary artery bypass grafts in whom dehiscence occurs less than 1 month after sternotomy. All others should have closure with muscle flaps.

	Introduction

Top Abstract Introduction Material and methods Results Comment References

 
The treatment of wound dehiscence after sternotomy underwent major advancements in 1963 when Shumacker and Mandelbaum [1] introduced closed-chest catheter antibiotic irrigation after sternal debridement and again in 1980 when closure with muscle flaps was introduced by Jurkiewicz and associates [2]. Since then, numerous investigators have refined the rewiring techniques and the process of irrigation by modifying irrigation fluids [3], and others have introduced new muscle flaps for the closure of these wounds. Grossi and co-workers [4] reviewed a series of 77 infected patients treated by catheter irrigation. A 90% success rate was obtained when reclosure and irrigation were performed within the first 3 weeks after sternotomy. However, this treatment was associated with an overall mortality rate of 22% as a result of persistent sepsis, organ failure, or both. In contrast, in a review [5] of 211 sternal infections treated with muscle flaps, successful wound closure occurred in 95% of patients and the mortality rate was 5.7%.

These experiences had led some institutions to adopt muscle flaps as the primary treatment for all patients with sternal wound infections [5]. However, because of concerns regarding the potential morbidity of muscle flaps [6] and the additional cost of another operation, many institutions have continued to employ catheter irrigation in the initial approach to sternal wound complications.

Although controversy remains regarding the application of irrigation and flaps in the acute setting, Pairolero and Arnold [7] resolved the conflict between the techniques when treating patients whose infection is diagnosed more than 1 month after sternotomy. In this setting, debridement and muscle flap closure should be the primary treatment in all patients. In such patients with a more chronic condition, these investigators attributed irrigation failure to the degree of mediastinal fibrosis present, which prevented suction catheters from obliterating dead space within the mediastinal cavity.

The increasing use of the internal mammary artery (IMA) in at least 80% of patients undergoing revascularization has altered the nature of the sternal wounds that are currently clinically encountered. The combination of diabetes and bilateral IMA grafts represents an increased risk of postoperative infection. Because the IMA is the primary blood supply to the sternum, there is frequently a substantial degree of ischemic necrosis of the bone on the side of the IMA graft. This is commonly encountered in the clinical setting. This factor requires close consideration when analyzing data from previous studies in which IMA status was not specifically considered and that were performed at a time when IMA grafts were less common [3, 4].

This study compared catheter irrigation and muscle flaps prospectively in an attempt to define their appropriate use.

	Material and methods

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During a 6-year period from 1990 to 1996, 6,356 sternotomies were performed at the University of Washington Medical Center. From 1990 to 1994 (n = 5,658 sternotomies), sternal wound dehiscence was observed in 43 patients (0.76%). A prospective treatment plan was used to evaluate the appropriate roles of debridement, closed-chest catheter antibiotic irrigation, sternal rewiring, and skin closure versus debridement and vascularized muscle or omental flap closure. No sternal wounds were treated with open dressings other than to initially drain a septic wound. Subsequent to this study period, from 1994 to 1996, 25 patients were treated according to the algorithm developed from the prospective trial.

Because of the relative infrequency of dehiscence and because documented infection was present in only 58.1% of dehiscences, it was decided not to randomize the patients into two treatment groups for the pilot investigation. Instead, each patient was treated initially by catheter irrigation if sternal restabilization could be established with rewiring techniques. This approach tested the null hypothesis that all patients with an acute condition should be closed primarily over irrigation catheters. Those patients whose sternum could not be restabilized and those patients whose wounds failed to heal during irrigation would have coverage with vascularized flaps. This approach was also a stronger test of muscle flap techniques than a straightforward randomization in that it compared the success of muscle flaps in individual patients in whom irrigation had failed. As such, each of the patients with a muscle flap effectively represented his or her own control.

Patients were analyzed according to the presence or absence of infection, the specific bacteriologic findings, the presence or absence of IMA bypass grafts, the presence of sternal fractures, and the ability to be restabilized by rewiring including the weave techniques of Robicsek and co-workers [8]. Outcome measures included wound resolution, length of hospitalization, and comparative complication rates.

Patients who presented with gross evidence of purulent wound drainage, fever, and sepsis were initially opened and drained before an attempt was made to close the wound with either irrigation or flap techniques. Otherwise single-stage debridements and closures over catheters or with muscle flaps were performed.

	Results

Top Abstract Introduction Material and methods Results Comment References

 
In the study group from 1990 to 1994, 43 patients were treated for sternal dehiscence, and 25 of them had documented infection on the basis of preoperative cultures grown at the time of initial wound drainage or intraoperative Gram’s stains and cultures. Eighteen patients were seen with a sterile sternal dehiscence. Table 1 depicts the categorization of patients as determined by presence or absence of infection, IMA bypass graft status, and type of primary therapy (irrigation or muscle flap closure).

Conversely, both patients with positive cultures who had not undergone IMA bypass grafting responded to irrigation with a healed and stable wound and required no further therapy. This was also the case for all 17 patients with sterile wound dehiscence who were treated by irrigation and in whom rigid sternal restabilization was accomplished. In these patients, irrigation was discontinued once cultures were negative.

There were 6 patients who had infection and IMA bypass grafts and whose sternums could not be restabilized. They underwent primary muscle flap closure and healed uneventfully. In the 1 patient without infection in whom rewiring did not accomplish restabilization, a flap resulted in successful healing.

In addition to those previously mentioned, other risk factors for treatment success that were evaluated included diabetes, repeat sternotomy, and organ failure. None of these factors revealed significant differences between the treatment groups except the presence of a sternal fracture, which potentially compromised the ability to restabilize the sternum.

Total length of hospitalization averaged 10.2 days for the patients having primary closure with a muscle flap. This was extended an average of 14.3 additional days when muscle flaps were preceded by an unsuccessful attempt at catheter irrigation. Average hospitalization for successful irrigation was 11.2 days. The difference is not significant.

A broad bacteriologic spectrum was encountered during this study, although Staphylococcus species were preponderant. There was no change in treatment technique or outcome in response to the specific pathogen. Culture-specific antibiotic irrigation fluids were used in all patients with infection who underwent catheter irrigation. Catheters were removed when the effluent no longer grew positive cultures.

Because of the results of this study, we now use the treatment algorithm in Figure 1 for sternal dehiscence. Between November 1994 and November 1996, we encountered 25 more patients with documented sternal infection who had undergone IMA bypass grafting. All were successfully treated primarily with muscle flaps according to the protocol, and none required further operative treatment.

View larger version (15K): [in this window] [in a new window]   Fig 1. Treatment algorithm for sternal dehiscence. (+IMA = internal mammary artery used for revascularization.)

	Comment

Top Abstract Introduction Material and methods Results Comment References

A previous attempt at a controlled study of these modalities was performed by Scully and colleagues [9] who divided 41 patients into two almost equal, consecutive groups. The first group of 19 patients was treated by irrigation, and subsequently the second group of 22 patients had flap closure. There were no differences in treatment outcome between the groups in terms of wound resolution, mortality, or other complications. Notably, there were no cosmetic or functional problems associated with the muscle flap techniques, a factor that had previously raised concerns about the morbidity of these procedures. Other studies [10] of the potential morbidity of muscle flaps also have shown no differences in late postoperative pulmonary function test results, exercise tolerance, and oxygen uptake compared with matched control groups. These conclusions were supported by our results. Our patients with muscle flaps were extubated within 24 hours despite the absence of sternal restabilization and chest wall continuity.

Clearly, a sternal wound infection is different from a sterile sternal dehiscence. Although many infections are obvious, determining the presence of infection in a patient who is seen with serous wound drainage, sternal instability, and absence of fever or sepsis is not always straightforward. Wound swabs or aspirates in contact with the skin may result in false-positive cultures in a patient whose mediastinum is actually sterile. Our current protocol in nonpurulent cases is to rely on intraoperative Gram’s stains and cultures and to clinically assess the bone and soft tissues and the potential for restabilization. If the Gram’s stain is negative for bacteria and the conditions are otherwise favorable for stable sternal closure with catheter irrigation, then this is the procedure performed. It is not dependent on IMA status.

However, on the basis of the results of this study, if the initial negative Gram’s stain subsequently becomes positive in a patient with an IMA graft, we advocate returning the patient to the operating room for flap closure even if the patient appears clinically stable during the irrigation process. Though we have not yet encountered this scenario, our results suggest that this patient has only an 11% likelihood of success without a flap. Morbidity and overall cost would be substantially reduced by prompt conversion to a muscle flap closure.

The single most critical component determining the success of therapy for sternal wound infections is the performance of complete debridement of infected and necrotic bone and exposed cartilage. Without this critical component, both irrigation and muscle flap techniques are associated with major risks of recurrent infection and sinus formation. Of great importance is the fact that previous evaluations of catheter irrigation were performed before the longer patency rates of IMA grafts were well documented. When this study began, approximately 80% of patients undergoing coronary revascularization had an IMA graft included in the procedure. This figure now approaches 100%.

Whether or not IMA grafts are actually causative in the etiology of sternal infection has been debated, but their usefulness in coronary revascularization far outweighs the potential risks involved. However, when wound infection does occur after IMA grafting, it is frequently associated with a greater degree of sternal necrosis on the side of the IMA graft, a finding not noted when the IMAs are not harvested. This is presumed to be due to the fact that the IMA provides the primary blood supply to the sternum [11] and that sternal blood flow has been shown to drop 90% after IMA harvest.

As a result, the degree of debridement of the infected sternum after IMA grafting is often greater than that required when the IMAs are intact and the sternal blood supply has not been interrupted. Our study has shown that muscle flaps are better for patients who have had revascularization with IMA grafts and then become infected. There is the possibility that the debridement of bone stops short of being adequate when there is to be an attempt to restabilize with wires and perform irrigation. This may have contributed to the 88.2% failure rate of irrigation in this study. Muscle flap closure does not have this limitation. The sternum can be debrided aggressively and to the extent required because no attempt will be made to rewire the remaining fragments.

Despite the success of muscle flaps, to treat all patients with sternal dehiscence by flap closure would be costly and unnecessary. On the basis of our results, we believe all patients without infection and patients with infection but without IMA grafts can be managed successfully with closure and irrigation if the sternum can be restabilized.

In summary, at our institution, therapeutic decisions on the management of sternal wound complications are based on the time of occurrence, the presence of an IMA graft, and the positive identification of infection by cultures. Patients with a positive culture or an unequivocal intraoperative Gram’s stain revealing bacteria are considered infected. For patients with IMA grafts and infection, irrigation is no longer used, and primary muscle flap closure is performed. Patients with an unstable sternum, whether or not they have infection, also have flap closure. The remaining patients are treated primarily with closed-chest catheter irrigation.

	References

Top Abstract Introduction Material and methods Results Comment References

 

1. Shumacker H.B., Jr, Mandelbaum I. Continuous antibiotic irrigation in the treatment of infection. Arch Surg 1963;86:384-387.
2. Jurkiewicz M.J., Bostwick J., Hester T.R., Bishop J.B., Craver J. Infected median sternotomy wound: successful treatment by muscle flaps. Ann Surg 1980;191:738-744.[Medline]
3. Culliford A.T., Cunningham J.N., Zeff R.H., Isom O.W., Teiko P., Spencer F. Sternal and costochondral infections following open-heart surgery: a review of 2,594 cases. J Thorac Cardiovasc Surg 1976;72:714-726.[Abstract]
4. Grossi E.A., Culliford A.T., Krieger K.H., et al. A survey of 77 major infectious complications of median sternotomy: a review of 7,949 consecutive operative procedures. Ann Thorac Surg 1985;40:214-223.[Abstract]
5. Nahai F., Rand R.P., Hester T.R., Bostwick J., Jurkiewicz M.J. Primary treatment of the infected sternotomy wound with muscle flaps: a review of 211 consecutive cases. Plast Reconstr Surg 1989;84:434-441.[Medline]
6. Ringelman P.R., Vander Kolk C.A., Cameron D., Baumgartner W.A., Manson P. Long-term results of flap reconstruction in median sternotomy wound infections. Plast Reconstr Surg 1994;93:1208-1216.[Medline]
7. Pairolero P.C., Arnold P.G. Management of recalcitrant median sternotomy wounds. J Thorac Cardiovasc Surg 1984;88:357-364.[Abstract]
8. Robicsek F., Daugherty H.K., Cook J.W. The prevention and treatment of sternum separation following open-heart surgery. J Thorac Cardiovasc Surg 1977;73:267-268.[Abstract]
9. Scully H., Leclerc Y., Martin R.D., et al. Comparison between antibiotic irrigation and mobilization of pectoral muscle flaps in treatment of deep sternal infections. J Thorac Cardiovasc Surg 1985;90:523-531.[Abstract]
10. Kohman L.J., Auchincloss J.H., Gilbert R., Beshara M. Functional results of muscle flap closure for sternal infection. Ann Thorac Surg 1991;52:102-106.[Abstract]
11. Arnold M. The surgical anatomy of sternal blood supply. J Thorac Cardiovasc Surg 1972;64:596-610.[Medline]

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Richard P. Cochran Salim Aziz Bradley O. Hofer Margaret D. Allen Edward D. Verrier Karyn S. Kunzelman Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Rand, R. P. Articles by Kunzelman, K. S. Search for Related Content PubMed PubMed Citation Articles by Rand, R. P. Articles by Kunzelman, K. S.