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Simplified treatment of postoperative mediastinitis
Simplified Treatment of Postoperative Mediastinitis CARDIOVASCULAR
Walter H. Merrill, MD, Shahab A. Akhter, MD, Randall K. Wolf, MD, E. William Schneeberger, MD, and John B. Flege, Jr, MD Department of Surgery and Heart and Vascular Center, Section of Cardiothoracic Surgery, University of Cincinnati, Cincinnati, Ohio
Background. Wound infection after median sternotomy for cardiac or thoracic surgery is a serious complication. A variety of treatment plans have been advocated, and there is lack of agreement regarding the best treatment method. We present our results in patients with mediastinitis who have been treated in a simple, consistent manner. Methods. We reviewed our experience with 40 consecutive patients with mediastinitis who were treated between January 1995 and May 2003 with a single-stage treatment consisting of sternal and soft tissue debridement and wound closure over mediastinal tubes with continuous irrigation and drainage. Tubes were placed posterior to the sternum in all patients and were irrigated continuously for at least 7 days with antibiotic or antibacterial solution. Systemic antibiotics were selected based on culture and sensitivity data and were administered for 2 to 6 weeks.
Results. All patients with mediastinitis treated in this manner survived. Of the 40 patients, 38 achieved complete healing of the wound without further operative intervention or major complication. One patient had recurrent infection and required sternal resection and advancement of muscle flaps. One patient had a residual localized focus of chondritis and underwent limited resection of cartilage. Conclusions. In this series of patients with postoperative mediastinitis, a simplified approach consisting of wound debridement, reclosure over drains, and anterior mediastinal irrigation has been an effective treatment. The results we have achieved suggest that this technique may be a suitable option for treating this condition.
W
Patients and Methods
ound infection after median sternotomy for cardiac or thoracic surgery is a serious and sometimes life-threatening complication. It is an important source of morbidity, mortality, and extra cost. While improved antibiotic prophylaxis and evolving surgical practices have reduced the incidence of mediastinitis, these infections continue to be an infrequent but not inconsequential problem. Many host risk factors have been implicated in the development of mediastinitis, as have various operative risk factors. Some authors have contended that specific postoperative complications increase the likelihood of developing sternal infections. Because postoperative mediastinitis occurs in 1% to 3% of patients undergoing median sternotomy and its associated mortality has been reported to be as high as 40%, it is important to develop treatment protocols to treat this condition reliably in an effort to reduce mortality, morbidity, and the cost associated with infection. A variety of treatment plans have been advocated over the years, and there is lack of agreement regarding the best method of treatment. We present our results in patients with mediastinitis after cardiac or thoracic surgery who have been treated in a simple, consistent manner. Accepted for publication Feb 18, 2004. Presented at the Fiftieth Annual Meeting of the Southern Thoracic Surgical Association, Bonita Springs, FL, Nov 13–15, 2003. Address reprint requests to Dr Merrill, 231 Albert B. Sabin Way, ML 0558, Cincinnati, OH 45267-0558; e-mail: [email protected].
© 2004 by The Society of Thoracic Surgeons Published by Elsevier Inc
(Ann Thorac Surg 2004;78:608 –12) © 2004 by The Society of Thoracic Surgeons
We reviewed the records of 40 consecutive patients with mediastinitis after cardiac or thoracic surgery who have been treated by the authors in four hospitals between January 1995 and May 2003. That represents an overall mediastinitis rate of 0.3%. Patient characteristics are summarized in Table 1. There were 36 male and 4 female patients. Patient ages ranged from 19 to 77 years, with a mean of 59.9 years. Two patients had undergone a previous cardiac procedure through a median sternotomy approach. The majority of patients were diabetic and required either insulin (22 patients) or oral agents (6 patients). One patient was on dialysis preoperatively and was HIV positive. Routine triple-drug immunosuppression therapy was employed perioperatively in 1 patient who underwent an orthotopic cardiac transplant. Procedures performed included coronary artery bypass (33 patients), mitral valve repair (2 patients), and aortic root replacement, Ross procedure, aortic valve replacement plus coronary artery bypass, heart transplant, and bilateral lung volume reduction (1 patient each). None of the procedures was performed as an emergency. One patient undergoing coronary artery bypass required a simultaneous carotid endarterectomy. Left internal thoracic artery mobilization and grafting of the left anterior descending coronary artery were performed in all first time coronary artery bypass cases. In 2 patients, bilateral internal thoracic artery grafting was 0003-4975/04/$30.00 doi:10.1016/j.athoracsur.2004.02.089
Ann Thorac Surg 2004;78:608 –12
MERRILL ET AL TREATING POSTOPERATIVE MEDIASTINITIS
Table 1. Patient Characteristics
Table 3. Patient Outcomes
59.9 36 4 2 12 6 22 1 1
performed. One patient who underwent coronary artery bypass grafting required intraoperative insertion of the intraaortic balloon pump. Four patients underwent reexploration for bleeding; 1 of them required two reexplorations. The diagnosis of mediastinitis was based on clinical findings. All patients met the criteria for deep surgical wound infection as defined by the Centers for Disease Control [1]. In each instance patients exhibited erythema and swelling of the sternotomy incision accompanied by drainage of purulent fluid and sternal instability. These findings were usually accompanied by fever, tachycardia, and leukocytosis. Patients with superficial sternal wound infections or sterile sternal dehiscences were not included in this study. Computed tomographic scanning of the chest was not employed routinely as a diagnostic technique. All patients were returned to the operating room for definitive single-stage treatment of the infected wound. Definite evidence of sternal osteomyelitis and an unstable sternum were noted in every patient. Patients were classified in accordance with the criteria proposed by El Oakley and Wright [2] (Table 2). Organisms cultured from the retrosternal space at the time of operation included Staphylococcus species (30 patients), various gram-negative organisms (9 patients), and Candida species (1 patient). Blood cultures were positive in 25% of cases. The interval between the primary operation and reoperation for infection ranged from 7 to 28 days, with a mean of 14.9 days. After thoroughly preparing and draping the chest, the median sternotomy incision was opened completely, and all sutures and sternal wires were removed. Intraoperative culture and Gram stain were obtained. The soft tissues were debrided as necessary, but as minimally as Table 2. Classification of Mediastinitis Class Type Type Type Type
Number I II III A III B
8 4 12 16
Mean Infection detected (postoperative day) Hospitalization after reintervention (days) Complete healing with primary reintervention Mortality
7–28 7–29 38/40 0
14.9 15
possible. The sternal edges were freshened with curettes and rongeurs, or they were treated by resecting 1 to 2 mm of sternal bone bilaterally with an oscillating saw in order to freshen the edges. The wound was copiously irrigated with warm saline or antibiotic solution. One or more drainage and irrigation catheters were placed in the mediastinum posterior to the sternal edges. The drainage and irrigation system consisted of a modified Mills sump tube or was composed of a multiple side hole catheter for infusion accompanied by a regular mediastinal drainage tube. The sternal edges were carefully and securely reapproximated with multiple heavy stainless steel wires. The skin edges and soft tissues were then reapproximated. All patients underwent high-volume mediastinal irrigation, at least 100 mL per hour, for a minimum of 7 days with antibiotic or antibacterial solution. Patients were administered dilute povidone (10 mL in 1,000 mL normal saline) or a dilute antibiotic solution (vancomycin or cephalosporin 1,000 mg in 1,000 mL normal saline). The irrigation solution was adjusted subsequently depending upon culture results. Systemic intravenous antibiotics were selected based on culture and sensitivity data and were administered for a 4- to 6-week course postoperatively.
Results Patient outcomes are summarized in Table 3. All patients were treated in essentially the same manner. In every instance, the patients underwent debridement and sternal reapproximation over drains as well as closure of the skin and soft tissues. All 40 patients with postoperative mediastinitis who were treated in this manner survived. Of the 40 patients treated, 38 achieved complete healing of the wound without further operative intervention or major complication as a result of this one-stage intervention. The interval from operation for mediastinitis to discharge from the hospital ranged from 7 to 29 days, with a mean of 15 days. At this time, complete healing of the mediastinal wound had been achieved. Two patients did not achieve primary healing and required further intervention. One patient had a recurrent infection and required reoperation, which included sternal resection with advancement of muscle flaps. In another patient, a residual localized focus of chondritis developed, and this patient subsequently underwent a limited resection of cartilage. In both instances, complete wound healing was obtained subsequent to the second intervention. There were no additional instances of delayed wound problems or re-
CARDIOVASCULAR
Number Mean age (years) Sex Male Female Prior sternotomy Diabetic status Nondiabetic Oral agents Insulin Dialysis Immunosuppression
609
610
MERRILL ET AL TREATING POSTOPERATIVE MEDIASTINITIS
quirement for additional surgical intervention. There were no perioperative myocardial infarctions related to treatment of mediastinitis. Graft patency after treatment for mediastinitis has not been assessed. CARDIOVASCULAR
Comment Mediastinitis after cardiac or thoracic surgery is a dreaded complication. It occurs in 1% to 2% of cases, and its associated morbidity, mortality, prolongation of hospital stay, and extra cost are all important issues. The cost of deep sternal infections is significant. It has been estimated in various studies to range between $26,000, in 1985, and $80,000 currently [3]. As noted by others, mediastinitis might result in additional problems, including lower patient satisfaction, fewer referrals for operation, and an increased risk of litigation. It has also been postulated that the morbidity, mortality, and extra cost associated with deep sternal infection imply that it might be more cost effective in some high-risk patients to undertake medical management as opposed to operative intervention [3]. Several authors have described various host risk factors that might contribute to the development of deep surgical site infections. These have been described extensively in the literature and include obesity, diabetes mellitus, the use of internal thoracic artery grafts (especially bilateral), advanced age, female sex, chronic lung disease, active smoking, prolonged mechanical ventilation, the use of steroids, and preoperative hospital stay longer than 5 days [3]. In addition, there are risk factors associated with the operative procedure that have been implicated in the development of mediastinitis. These include the duration of operation, the duration of cardiopulmonary bypass, the use of the intraaortic balloon pump, reoperation for bleeding, and other factors such as extensive use of electrocautery, the use of bone wax, and hair removal with a razor rather than clippers [3]. Some authors have noted that the placement of an intraaortic balloon pump during or after the primary operative procedure was associated with an increased risk of mediastinitis. This association possibly reflects a relationship between lower cardiac output, overall tissue perfusion, and infection [4]. Some authors have attempted to identify postoperative complications that might increase the likelihood of developing sternal infections. Factors noted that were of importance included operative reexploration for bleeding and transfusion of blood products [5]. Efforts to reduce the incidence of mediastinitis have achieved some success. Several authors have focused on the use of mechanical clippers rather than razors for hair removal, scrupulous attention to the timing of preoperative antibiotic administration and repeating antibiotic administration during the later stages of the operative procedure [4], and institution of strict policies to control blood glucose levels perioperatively [6]. Other authors have also related the risk of wound infection to blood glucose levels after open heart procedures [7]. Additional preventative measures that might possibly lower the incidence of mediastinitis include careful at-
Ann Thorac Surg 2004;78:608 –12
tention to the details of internal thoracic artery mobilization and length, possibly avoiding internal thoracic artery grafting in high-risk patients, avoiding foreign bodies such as bone wax that might impede bone healing, and close monitoring of hospital equipment and personnel [8]. Various authors have recommended a host of diagnostic tests to reliably identify mediastinitis. These have included such tests as C-reactive protein measurement, computed tomography, 99Tcm-labeled leukocyte scintigraphy, and single-photon emission computed tomography [9]. In our series, all patients were diagnosed with mediastinitis based on simple observation of clinical findings, which were consistent with both the criteria defined by the Centers for Disease Control [1] and those proposed by El Oakley and Wright [2]. Other authors have reported the occurrence of significant bleeding related to the development of mediastinitis. They have noted that right ventricular rupture is the most common source of major bleeding, but bleeding can also occur from other sites such as the aorta, right atrium, and bypass grafts or prosthetic aortic grafts. This is a dreaded complication because even with aggressive treatment the mortality associated with this problem remains quite high. Unfortunately infection can spread to involve all areas of the mediastinum including the anastomoses and cannulation sites [10]. Fortunately, we have not observed this complication in our patients. The absence of major mediastinal bleeding in this series may have been related to frequent use of a pericardial flap to facilitate coverage of the heart and bypass grafts, thus sealing the heart from the back of the sternum and limiting the likelihood of infection penetrating deep into the mediastinum [11]. Other authors have stated that the use of the pericardial flap interposes a pedicle of vascularized tissue between the heart and the sternum, and when done appropriately it does not involve risk of tamponade or graft compression. They have also stated that possibly the use of the pericardial flap prevents sternal infection [12], although we have not found that to be true. Multiple treatment modalities have been proposed for mediastinitis. These vary from simple observation with prolonged antibiotic administration to local dressing changes to limited wound debridement to partial or complete sternectomy combined with advancement of muscle or omental flaps [2]. In 1963, Shumacker and Mandelbaum [13] described the technique of wound debridement, primary sternal closure, and closed mediastinal irrigation. Reports on the results of this technique have been variable. In our opinion, high-volume irrigation is an important aspect of the treatment regimen. We hypothesize that the results we have achieved are due, at least in part, to the consistent use of high-volume irrigation in our patients. We also contend that the ability to achieve prompt stabilization of the sternal halves with this procedure affords a major advantage. Chest wall dynamics are optimized, which can be critically important, particularly in patients with compromised lung function. Some authors have stated that if gross purulence is
encountered within the mediastinum, the contamination is best treated with drainage, wound care, and secondary reconstruction [8]. Our approach has been to perform debridement, sternal reapproximation, and wound closure over drains whenever possible. Therefore, we have not altered our technique based on results of the intraoperative Gram stain. Other authors state that Candida mediastinitis has been a particularly difficult problem. It has been postulated that muscle flap or reconstruction with omentum should be utilized in these situations [14]. Our experience, although limited, suggests that the simplified technique we have employed can be successful even in immunosuppressed patients with Candida mediastinitis. In recent years, vacuum-assisted closure has been advocated as a treatment for mediastinitis. This consists of the application of polyurethane foam, which is embedded with a noncollapsible evacuation tube, a vacuum pump, and transparent adhesive drape. It has been reported that this leads to development of a prompt and moderately stable sternal repair due to fibrous union. The technique provides evacuation of wound fluid, decreases bacterial colonization, stimulates granulation tissue, and reduces the frequency of dressing changes [15]. It can be used as definitive therapy or it can be used to clean the wound in preparation for subsequent wound closure with flaps [16]. While many authors currently favor the vacuumassisted technique (VAC) for patients with mediastinitis, several published reports suggest that this method may have several problems associated with it. Obdeijn and colleagues [15] reported 3 patients who required the VAC for 21 to 49 days to achieve wound healing. Catarino and associates [17] reported 9 patients who required the VAC for 12 to 34 days (median, 15) before delayed primary closure in order to achieve wound healing. Fleck and colleagues [18] reported 11 patients who required the VAC for 4 to 15 days (mean, 9.3) before either reconstruction with a pectoralis muscle flap (54.5%) or delayed primary wound closure (45.5%). Hospital stay ranged from 13 to 45 days (median, 30). Luckraz and associates [19] reported 14 patients treated with VAC, with 4 deaths, median duration of VAC 13.5 days, and median hospital stay of 20 days, excluding 4 patients who died and 4 others who were transferred to another hospital. Overall, 64% of patients treated in this manner survived with a satisfactorily healed incision. They also reported 13 patients treated with VAC followed by a myocutaneous flap or delayed primary closure. This latter group had a 7.7% mortality rate, and only 10 of the 13 patients (77%) achieved a healed stable sternum. Domkowski and colleagues [16] reported 53 patients treated with VAC who were allowed to heal by secondary closure; 2 of these patients died. An additional 43 patients had VAC followed by omental transposition or pectoralis flap, and 2 of these patients died. Abu-Omar and colleagues [20] reported 2 patients treated with VAC in whom right ventricular rupture developed, both of whom required emergency operative repair. We have noted the comments of Domkowski and colleagues [16], who stated that the results in their study
MERRILL ET AL TREATING POSTOPERATIVE MEDIASTINITIS
611
of patients treated with VAC “support the role of the wound vacuum not only as an effective treatment tool but also to significantly lower mortality.” While this may be true, we agree with their statement that “a controlled randomized study would be necessary to determine if the wound vacuum device significantly lowered mortality and morbidity compared with historical treatment modalities. . . .” We have also noted the comments of Francel [21], who stated: “The only benefit we see for the VAC system in CABG patients is to support the sternal edges and maybe decrease the depth of the wound to allow the use of the pectoralis major muscles alone for coverage and avoid the donor complications of harvesting rectus abdominal muscle or the omentum.” We contrast these published results concerning VAC usage with a summary of the results of the current series in which the mean duration of hospital stay after intervention for mediastinitis was 15 days. Complete wound healing was achieved with one intervention in 38 of 40 patients and was accomplished with a second procedure in the remaining 2 patients. In addition, there were no deaths. As stated above, we think that the simplified technique we have utilized offers the following advantages: prompt stabilization of the sternum to facilitate healing and to promote normal chest wall dynamics; lack of necessity for dressing changes; and prompt wound healing in most instances. We postulate that the results we have achieved may be due to the use of high-volume irrigation and the frequent use of a pericardial flap to prevent penetration of infection deeper into the mediastinum to involve the heart, aorta, and bypass grafts. Mediastinitis after cardiac or thoracic surgery is a serious complication with major implications regarding morbidity, mortality, and extra cost. We have had good success in treating this complication with aggressive early debridement, closure of the wound over mediastinal drains, use of high-volume mediastinal irrigation, and intravenous antibiotics. Other treatment strategies are available, but we favor this simplified approach. The results obtained thus far suggest that this technique may be a suitable option for the treatment of postoperative mediastinitis.
References 1. Garner JS, Jarvis WR, Emori TG, Horan TC, Hughes JM. CDC definitions for nosocomial infections, 1988. Am J Infect Control 1988;16:128 –40. 2. El Oakley RM, Wright JE. Postoperative mediastinitis: classification and management. Ann Thorac Surg 1996;61: 1030 –6. 3. Hollenbeak CS, Murphy DM, Koenig S, Woodward RS, Dunagan WC, Fraser VJ. The clinical and economic impact of deep chest surgical site infections following coronary artery bypass graft surgery. Chest 2000;118:397–402. 4. Olsen MA, Lock-Buckley P, Hopkins D, Polish LB, Sundt TM, Fraser VJ. The risk factors for deep and superficial chest surgical-site infections after coronary artery bypass graft surgery are different. J Thorac Cardiovasc Surg 2002;124:136 – 45. 5. Zacharias A, Habib RH. Factors predisposing to median sternotomy complications. Deep vs superficial infections. Chest 1996;110:1173–8.
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6. Estrada CA, Young JA, Nifong LW, Chitwood WR Jr. Outcomes and perioperative hyperglycemia in patients with or without diabetes mellitus undergoing coronary artery bypass grafting. Ann Thorac Surg 2003;75:1392–9. 7. Zerr KJ, Furnary AP, Grunkemeier GL, Bookin S, Kanhere V, Starr A. Glucose control lowers the risk of wound infection in diabetics after open heart operations. Ann Thorac Surg 1997;63:356 –61. 8. Francel TJ, Kouchoukos NT. A rational approach to wound difficulties after sternotomy: the problem. Ann Thorac Surg 2001;72:1411–8. 9. Fowler VG, Kaye KS, Simel DL, et al. Staphylococcus aureus bacteremia after median sternotomy. Clinical utility of blood culture results in the identification of postoperative mediastinitis. Circulation 2003;108:73–8. 10. Yellin A, Refaely Y, Paley M, Simansky D. Major bleeding complicating deep sternal infection after cardiac surgery. J Thorac Cardiovasc Surg 2003;125:554 –8. 11. Flege JB Jr. Pericardial incision for internal mammary artery coronary bypass. Ann Thorac Surg 1987;44:424. 12. Nugent WC, Maislen EL, O’Connor GT, Marrin CAS, Plume SK. Pericardial flap prevents sternal wound complications. Arch Surg 1988;123:636 –9. 13. Shumacker HB, Mandelbaum I. Continuous antibiotic irrigation in the treatment of infection. Arch Surg 1963;86:384 –7. 14. Francel TJ, Kouchoukos NT. A rational approach to wound
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difficulties after sternotomy: reconstruction and long-term results. Ann Thorac Surg 2001;72:1419 –29. Obdeijn MC, de Lange MY, Lichtendahl DHE, de Boer WJ. Vacuum-assisted closure in the treatment of poststernotomy mediastinitis. Ann Thorac Surg 1999;68:2358 –60. Domkowski PW, Smith ML, Gonyon DL Jr, et al. Evaluation of vacuum-assisted closure in the treatment of poststernotomy mediastinitis. J Thorac Cardiovasc Surg 2003;126:386 – 90. Catarino PA, Chamberlain MH, Wright NC, et al. Highpressure suction drainage via a polyurethane foam in the management of poststernotomy mediastinstinitis. Ann Thorac Surg 2000;70:1891–5. Fleck TM, Fleck M, Moidl R, et al. The vacuum-assisted closure system for the treatment of deep sternal wound infections after cardiac surgery. Ann Thorac Surg 2002;74: 1596 –600. Luckraz H, Murphy F, Bryants S, Charman SC, Ritchie AJ. Vacuum-assisted closure as a treatment modality for infections after cardiac surgery. J Thorac Cardiovasc Surg 2003; 125:301–5. Abu-Omar Y, Naik MJ, Catarino PA, Ratnatunga C. Right ventricular rupture during use of high-pressure suction drainage in the management of poststernotomy mediastinitis. Ann Thorac Surg 2003;76:974. Francel TJ. Invited commentary. Ann Thorac Surg 2002;74: 1600.
DISCUSSION DR RICHARD L. PRAGER (Ann Arbor, MI): Dr Merrill, thank you for taking us back to the future because I think that is what you have done. I rise to commend you for reminding us about wound healing and would care because I think that is an essential part of this and I think you have really discussed that in exemplary fashion, as well as in the text, reconvincing us that this is most often a clinical diagnosis, not a computerized tomography scan diagnosis. I have three brief questions. First, are you really content reclosing the sternum and putting drainage systems in those patients who have extensive ascending or transverse aortic reconstruction with graft material? Second, it is my sense that these irrigation systems are not really soaker hoses, but they are just 7 days of a parallel tract that only irrigates the tract and therefore do not truly irrigate the mediastinum. I would like your thoughts about these two issues. And finally, is there anyone that you would actually flap as the primary procedure? I enjoyed the paper very much. Thanks, Dr Merrill. DR MERRILL: I will answer your questions as well as I can. Thank you for being so kind in your comments. Fortunately, we have not experienced instances of deep mediastinal infection involving bypass grafts or grafts in the aorta, cannulation sites, etcetera. This is perhaps due in part to the fairly routine use of a pericardial flap to cover over the anterior surface of the heart prior to closing the sternum at the time of the primary procedure. This is a strategy that was proposed by my colleague, Dr Flege, a number of years ago, and we think that perhaps this has helped prevent these deep infections. So for the most part we have felt content in closing the wound as described in the presentation. If there is no evidence of a space problem at the time of the operation for mediastinitis we have used the technique described. However, if we did encounter a situation in which there was mediastinal scarring or a deep space problem that might persist, then we would consider an alternative technique.
DR WALTER G. WOLFE (Durham, NC): I enjoyed going back to the future again, as you said. I think this is appropriate if you have a bone that you can put back together. I would like to know what you do with the brisket sternum. What were the white counts in these patients, how many had positive blood cultures, and what were the culture results from your wounds, because in our experience most of the time the bone can’t be reapproximated and you are left with needing living tissue to fill that space? So I just wonder, it seems like you had an unusual group of patients. At least the ones who are referred in to us, most of the time you have positive blood cultures and a brisket sternum. The Wound-Vac we feel is the most important part of the early management, but still, if you can’t put the bone back together, which in our experience is the majority of the cases, I think your group is kind of skewed here to the right or the left of center, whichever side you want to go to. I appreciate your comments. DR MERRILL: Thank you for your remarks. Clearly you have raised several really important points. The key, I think, in achieving success with this or any technique is careful and stable reapproximation of the tissues, particularly the sternum, in order to help facilitate wound healing. Several times I have shared great concern with my colleagues in approaching these patients when the sternum seemed to be quite soft, and we were very worried whether or not we would be able to achieve healing. However, after taking adequate time to work on the sternum with rongeurs, curettes or shaving off the edges with a saw, we are usually left with enough sternum to bring together. We postulate that a lot of wires placed and tightened very carefully will bring the edges back together and achieve stability satisfactorily in most cases. I did not mention white blood cell counts in the presentation, but routinely these patients have leukocytosis. Many of them have positive blood cultures at the time of operation, as well as positive cultures from the mediastinum.
Walter H. Merrill, MD, Shahab A. Akhter, MD, Randall K. Wolf, MD, E. William Schneeberger, MD, and John B. Flege, Jr, MD Department of Surgery and Heart and Vascular Center, Section of Cardiothoracic Surgery, University of Cincinnati, Cincinnati, Ohio
Background. Wound infection after median sternotomy for cardiac or thoracic surgery is a serious complication. A variety of treatment plans have been advocated, and there is lack of agreement regarding the best treatment method. We present our results in patients with mediastinitis who have been treated in a simple, consistent manner. Methods. We reviewed our experience with 40 consecutive patients with mediastinitis who were treated between January 1995 and May 2003 with a single-stage treatment consisting of sternal and soft tissue debridement and wound closure over mediastinal tubes with continuous irrigation and drainage. Tubes were placed posterior to the sternum in all patients and were irrigated continuously for at least 7 days with antibiotic or antibacterial solution. Systemic antibiotics were selected based on culture and sensitivity data and were administered for 2 to 6 weeks.
Results. All patients with mediastinitis treated in this manner survived. Of the 40 patients, 38 achieved complete healing of the wound without further operative intervention or major complication. One patient had recurrent infection and required sternal resection and advancement of muscle flaps. One patient had a residual localized focus of chondritis and underwent limited resection of cartilage. Conclusions. In this series of patients with postoperative mediastinitis, a simplified approach consisting of wound debridement, reclosure over drains, and anterior mediastinal irrigation has been an effective treatment. The results we have achieved suggest that this technique may be a suitable option for treating this condition.
W
Patients and Methods
ound infection after median sternotomy for cardiac or thoracic surgery is a serious and sometimes life-threatening complication. It is an important source of morbidity, mortality, and extra cost. While improved antibiotic prophylaxis and evolving surgical practices have reduced the incidence of mediastinitis, these infections continue to be an infrequent but not inconsequential problem. Many host risk factors have been implicated in the development of mediastinitis, as have various operative risk factors. Some authors have contended that specific postoperative complications increase the likelihood of developing sternal infections. Because postoperative mediastinitis occurs in 1% to 3% of patients undergoing median sternotomy and its associated mortality has been reported to be as high as 40%, it is important to develop treatment protocols to treat this condition reliably in an effort to reduce mortality, morbidity, and the cost associated with infection. A variety of treatment plans have been advocated over the years, and there is lack of agreement regarding the best method of treatment. We present our results in patients with mediastinitis after cardiac or thoracic surgery who have been treated in a simple, consistent manner. Accepted for publication Feb 18, 2004. Presented at the Fiftieth Annual Meeting of the Southern Thoracic Surgical Association, Bonita Springs, FL, Nov 13–15, 2003. Address reprint requests to Dr Merrill, 231 Albert B. Sabin Way, ML 0558, Cincinnati, OH 45267-0558; e-mail: [email protected].
© 2004 by The Society of Thoracic Surgeons Published by Elsevier Inc
(Ann Thorac Surg 2004;78:608 –12) © 2004 by The Society of Thoracic Surgeons
We reviewed the records of 40 consecutive patients with mediastinitis after cardiac or thoracic surgery who have been treated by the authors in four hospitals between January 1995 and May 2003. That represents an overall mediastinitis rate of 0.3%. Patient characteristics are summarized in Table 1. There were 36 male and 4 female patients. Patient ages ranged from 19 to 77 years, with a mean of 59.9 years. Two patients had undergone a previous cardiac procedure through a median sternotomy approach. The majority of patients were diabetic and required either insulin (22 patients) or oral agents (6 patients). One patient was on dialysis preoperatively and was HIV positive. Routine triple-drug immunosuppression therapy was employed perioperatively in 1 patient who underwent an orthotopic cardiac transplant. Procedures performed included coronary artery bypass (33 patients), mitral valve repair (2 patients), and aortic root replacement, Ross procedure, aortic valve replacement plus coronary artery bypass, heart transplant, and bilateral lung volume reduction (1 patient each). None of the procedures was performed as an emergency. One patient undergoing coronary artery bypass required a simultaneous carotid endarterectomy. Left internal thoracic artery mobilization and grafting of the left anterior descending coronary artery were performed in all first time coronary artery bypass cases. In 2 patients, bilateral internal thoracic artery grafting was 0003-4975/04/$30.00 doi:10.1016/j.athoracsur.2004.02.089
Ann Thorac Surg 2004;78:608 –12
MERRILL ET AL TREATING POSTOPERATIVE MEDIASTINITIS
Table 1. Patient Characteristics
Table 3. Patient Outcomes
59.9 36 4 2 12 6 22 1 1
performed. One patient who underwent coronary artery bypass grafting required intraoperative insertion of the intraaortic balloon pump. Four patients underwent reexploration for bleeding; 1 of them required two reexplorations. The diagnosis of mediastinitis was based on clinical findings. All patients met the criteria for deep surgical wound infection as defined by the Centers for Disease Control [1]. In each instance patients exhibited erythema and swelling of the sternotomy incision accompanied by drainage of purulent fluid and sternal instability. These findings were usually accompanied by fever, tachycardia, and leukocytosis. Patients with superficial sternal wound infections or sterile sternal dehiscences were not included in this study. Computed tomographic scanning of the chest was not employed routinely as a diagnostic technique. All patients were returned to the operating room for definitive single-stage treatment of the infected wound. Definite evidence of sternal osteomyelitis and an unstable sternum were noted in every patient. Patients were classified in accordance with the criteria proposed by El Oakley and Wright [2] (Table 2). Organisms cultured from the retrosternal space at the time of operation included Staphylococcus species (30 patients), various gram-negative organisms (9 patients), and Candida species (1 patient). Blood cultures were positive in 25% of cases. The interval between the primary operation and reoperation for infection ranged from 7 to 28 days, with a mean of 14.9 days. After thoroughly preparing and draping the chest, the median sternotomy incision was opened completely, and all sutures and sternal wires were removed. Intraoperative culture and Gram stain were obtained. The soft tissues were debrided as necessary, but as minimally as Table 2. Classification of Mediastinitis Class Type Type Type Type
Number I II III A III B
8 4 12 16
Mean Infection detected (postoperative day) Hospitalization after reintervention (days) Complete healing with primary reintervention Mortality
7–28 7–29 38/40 0
14.9 15
possible. The sternal edges were freshened with curettes and rongeurs, or they were treated by resecting 1 to 2 mm of sternal bone bilaterally with an oscillating saw in order to freshen the edges. The wound was copiously irrigated with warm saline or antibiotic solution. One or more drainage and irrigation catheters were placed in the mediastinum posterior to the sternal edges. The drainage and irrigation system consisted of a modified Mills sump tube or was composed of a multiple side hole catheter for infusion accompanied by a regular mediastinal drainage tube. The sternal edges were carefully and securely reapproximated with multiple heavy stainless steel wires. The skin edges and soft tissues were then reapproximated. All patients underwent high-volume mediastinal irrigation, at least 100 mL per hour, for a minimum of 7 days with antibiotic or antibacterial solution. Patients were administered dilute povidone (10 mL in 1,000 mL normal saline) or a dilute antibiotic solution (vancomycin or cephalosporin 1,000 mg in 1,000 mL normal saline). The irrigation solution was adjusted subsequently depending upon culture results. Systemic intravenous antibiotics were selected based on culture and sensitivity data and were administered for a 4- to 6-week course postoperatively.
Results Patient outcomes are summarized in Table 3. All patients were treated in essentially the same manner. In every instance, the patients underwent debridement and sternal reapproximation over drains as well as closure of the skin and soft tissues. All 40 patients with postoperative mediastinitis who were treated in this manner survived. Of the 40 patients treated, 38 achieved complete healing of the wound without further operative intervention or major complication as a result of this one-stage intervention. The interval from operation for mediastinitis to discharge from the hospital ranged from 7 to 29 days, with a mean of 15 days. At this time, complete healing of the mediastinal wound had been achieved. Two patients did not achieve primary healing and required further intervention. One patient had a recurrent infection and required reoperation, which included sternal resection with advancement of muscle flaps. In another patient, a residual localized focus of chondritis developed, and this patient subsequently underwent a limited resection of cartilage. In both instances, complete wound healing was obtained subsequent to the second intervention. There were no additional instances of delayed wound problems or re-
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Number Mean age (years) Sex Male Female Prior sternotomy Diabetic status Nondiabetic Oral agents Insulin Dialysis Immunosuppression
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quirement for additional surgical intervention. There were no perioperative myocardial infarctions related to treatment of mediastinitis. Graft patency after treatment for mediastinitis has not been assessed. CARDIOVASCULAR
Comment Mediastinitis after cardiac or thoracic surgery is a dreaded complication. It occurs in 1% to 2% of cases, and its associated morbidity, mortality, prolongation of hospital stay, and extra cost are all important issues. The cost of deep sternal infections is significant. It has been estimated in various studies to range between $26,000, in 1985, and $80,000 currently [3]. As noted by others, mediastinitis might result in additional problems, including lower patient satisfaction, fewer referrals for operation, and an increased risk of litigation. It has also been postulated that the morbidity, mortality, and extra cost associated with deep sternal infection imply that it might be more cost effective in some high-risk patients to undertake medical management as opposed to operative intervention [3]. Several authors have described various host risk factors that might contribute to the development of deep surgical site infections. These have been described extensively in the literature and include obesity, diabetes mellitus, the use of internal thoracic artery grafts (especially bilateral), advanced age, female sex, chronic lung disease, active smoking, prolonged mechanical ventilation, the use of steroids, and preoperative hospital stay longer than 5 days [3]. In addition, there are risk factors associated with the operative procedure that have been implicated in the development of mediastinitis. These include the duration of operation, the duration of cardiopulmonary bypass, the use of the intraaortic balloon pump, reoperation for bleeding, and other factors such as extensive use of electrocautery, the use of bone wax, and hair removal with a razor rather than clippers [3]. Some authors have noted that the placement of an intraaortic balloon pump during or after the primary operative procedure was associated with an increased risk of mediastinitis. This association possibly reflects a relationship between lower cardiac output, overall tissue perfusion, and infection [4]. Some authors have attempted to identify postoperative complications that might increase the likelihood of developing sternal infections. Factors noted that were of importance included operative reexploration for bleeding and transfusion of blood products [5]. Efforts to reduce the incidence of mediastinitis have achieved some success. Several authors have focused on the use of mechanical clippers rather than razors for hair removal, scrupulous attention to the timing of preoperative antibiotic administration and repeating antibiotic administration during the later stages of the operative procedure [4], and institution of strict policies to control blood glucose levels perioperatively [6]. Other authors have also related the risk of wound infection to blood glucose levels after open heart procedures [7]. Additional preventative measures that might possibly lower the incidence of mediastinitis include careful at-
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tention to the details of internal thoracic artery mobilization and length, possibly avoiding internal thoracic artery grafting in high-risk patients, avoiding foreign bodies such as bone wax that might impede bone healing, and close monitoring of hospital equipment and personnel [8]. Various authors have recommended a host of diagnostic tests to reliably identify mediastinitis. These have included such tests as C-reactive protein measurement, computed tomography, 99Tcm-labeled leukocyte scintigraphy, and single-photon emission computed tomography [9]. In our series, all patients were diagnosed with mediastinitis based on simple observation of clinical findings, which were consistent with both the criteria defined by the Centers for Disease Control [1] and those proposed by El Oakley and Wright [2]. Other authors have reported the occurrence of significant bleeding related to the development of mediastinitis. They have noted that right ventricular rupture is the most common source of major bleeding, but bleeding can also occur from other sites such as the aorta, right atrium, and bypass grafts or prosthetic aortic grafts. This is a dreaded complication because even with aggressive treatment the mortality associated with this problem remains quite high. Unfortunately infection can spread to involve all areas of the mediastinum including the anastomoses and cannulation sites [10]. Fortunately, we have not observed this complication in our patients. The absence of major mediastinal bleeding in this series may have been related to frequent use of a pericardial flap to facilitate coverage of the heart and bypass grafts, thus sealing the heart from the back of the sternum and limiting the likelihood of infection penetrating deep into the mediastinum [11]. Other authors have stated that the use of the pericardial flap interposes a pedicle of vascularized tissue between the heart and the sternum, and when done appropriately it does not involve risk of tamponade or graft compression. They have also stated that possibly the use of the pericardial flap prevents sternal infection [12], although we have not found that to be true. Multiple treatment modalities have been proposed for mediastinitis. These vary from simple observation with prolonged antibiotic administration to local dressing changes to limited wound debridement to partial or complete sternectomy combined with advancement of muscle or omental flaps [2]. In 1963, Shumacker and Mandelbaum [13] described the technique of wound debridement, primary sternal closure, and closed mediastinal irrigation. Reports on the results of this technique have been variable. In our opinion, high-volume irrigation is an important aspect of the treatment regimen. We hypothesize that the results we have achieved are due, at least in part, to the consistent use of high-volume irrigation in our patients. We also contend that the ability to achieve prompt stabilization of the sternal halves with this procedure affords a major advantage. Chest wall dynamics are optimized, which can be critically important, particularly in patients with compromised lung function. Some authors have stated that if gross purulence is
encountered within the mediastinum, the contamination is best treated with drainage, wound care, and secondary reconstruction [8]. Our approach has been to perform debridement, sternal reapproximation, and wound closure over drains whenever possible. Therefore, we have not altered our technique based on results of the intraoperative Gram stain. Other authors state that Candida mediastinitis has been a particularly difficult problem. It has been postulated that muscle flap or reconstruction with omentum should be utilized in these situations [14]. Our experience, although limited, suggests that the simplified technique we have employed can be successful even in immunosuppressed patients with Candida mediastinitis. In recent years, vacuum-assisted closure has been advocated as a treatment for mediastinitis. This consists of the application of polyurethane foam, which is embedded with a noncollapsible evacuation tube, a vacuum pump, and transparent adhesive drape. It has been reported that this leads to development of a prompt and moderately stable sternal repair due to fibrous union. The technique provides evacuation of wound fluid, decreases bacterial colonization, stimulates granulation tissue, and reduces the frequency of dressing changes [15]. It can be used as definitive therapy or it can be used to clean the wound in preparation for subsequent wound closure with flaps [16]. While many authors currently favor the vacuumassisted technique (VAC) for patients with mediastinitis, several published reports suggest that this method may have several problems associated with it. Obdeijn and colleagues [15] reported 3 patients who required the VAC for 21 to 49 days to achieve wound healing. Catarino and associates [17] reported 9 patients who required the VAC for 12 to 34 days (median, 15) before delayed primary closure in order to achieve wound healing. Fleck and colleagues [18] reported 11 patients who required the VAC for 4 to 15 days (mean, 9.3) before either reconstruction with a pectoralis muscle flap (54.5%) or delayed primary wound closure (45.5%). Hospital stay ranged from 13 to 45 days (median, 30). Luckraz and associates [19] reported 14 patients treated with VAC, with 4 deaths, median duration of VAC 13.5 days, and median hospital stay of 20 days, excluding 4 patients who died and 4 others who were transferred to another hospital. Overall, 64% of patients treated in this manner survived with a satisfactorily healed incision. They also reported 13 patients treated with VAC followed by a myocutaneous flap or delayed primary closure. This latter group had a 7.7% mortality rate, and only 10 of the 13 patients (77%) achieved a healed stable sternum. Domkowski and colleagues [16] reported 53 patients treated with VAC who were allowed to heal by secondary closure; 2 of these patients died. An additional 43 patients had VAC followed by omental transposition or pectoralis flap, and 2 of these patients died. Abu-Omar and colleagues [20] reported 2 patients treated with VAC in whom right ventricular rupture developed, both of whom required emergency operative repair. We have noted the comments of Domkowski and colleagues [16], who stated that the results in their study
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of patients treated with VAC “support the role of the wound vacuum not only as an effective treatment tool but also to significantly lower mortality.” While this may be true, we agree with their statement that “a controlled randomized study would be necessary to determine if the wound vacuum device significantly lowered mortality and morbidity compared with historical treatment modalities. . . .” We have also noted the comments of Francel [21], who stated: “The only benefit we see for the VAC system in CABG patients is to support the sternal edges and maybe decrease the depth of the wound to allow the use of the pectoralis major muscles alone for coverage and avoid the donor complications of harvesting rectus abdominal muscle or the omentum.” We contrast these published results concerning VAC usage with a summary of the results of the current series in which the mean duration of hospital stay after intervention for mediastinitis was 15 days. Complete wound healing was achieved with one intervention in 38 of 40 patients and was accomplished with a second procedure in the remaining 2 patients. In addition, there were no deaths. As stated above, we think that the simplified technique we have utilized offers the following advantages: prompt stabilization of the sternum to facilitate healing and to promote normal chest wall dynamics; lack of necessity for dressing changes; and prompt wound healing in most instances. We postulate that the results we have achieved may be due to the use of high-volume irrigation and the frequent use of a pericardial flap to prevent penetration of infection deeper into the mediastinum to involve the heart, aorta, and bypass grafts. Mediastinitis after cardiac or thoracic surgery is a serious complication with major implications regarding morbidity, mortality, and extra cost. We have had good success in treating this complication with aggressive early debridement, closure of the wound over mediastinal drains, use of high-volume mediastinal irrigation, and intravenous antibiotics. Other treatment strategies are available, but we favor this simplified approach. The results obtained thus far suggest that this technique may be a suitable option for the treatment of postoperative mediastinitis.
References 1. Garner JS, Jarvis WR, Emori TG, Horan TC, Hughes JM. CDC definitions for nosocomial infections, 1988. Am J Infect Control 1988;16:128 –40. 2. El Oakley RM, Wright JE. Postoperative mediastinitis: classification and management. Ann Thorac Surg 1996;61: 1030 –6. 3. Hollenbeak CS, Murphy DM, Koenig S, Woodward RS, Dunagan WC, Fraser VJ. The clinical and economic impact of deep chest surgical site infections following coronary artery bypass graft surgery. Chest 2000;118:397–402. 4. Olsen MA, Lock-Buckley P, Hopkins D, Polish LB, Sundt TM, Fraser VJ. The risk factors for deep and superficial chest surgical-site infections after coronary artery bypass graft surgery are different. J Thorac Cardiovasc Surg 2002;124:136 – 45. 5. Zacharias A, Habib RH. Factors predisposing to median sternotomy complications. Deep vs superficial infections. Chest 1996;110:1173–8.
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6. Estrada CA, Young JA, Nifong LW, Chitwood WR Jr. Outcomes and perioperative hyperglycemia in patients with or without diabetes mellitus undergoing coronary artery bypass grafting. Ann Thorac Surg 2003;75:1392–9. 7. Zerr KJ, Furnary AP, Grunkemeier GL, Bookin S, Kanhere V, Starr A. Glucose control lowers the risk of wound infection in diabetics after open heart operations. Ann Thorac Surg 1997;63:356 –61. 8. Francel TJ, Kouchoukos NT. A rational approach to wound difficulties after sternotomy: the problem. Ann Thorac Surg 2001;72:1411–8. 9. Fowler VG, Kaye KS, Simel DL, et al. Staphylococcus aureus bacteremia after median sternotomy. Clinical utility of blood culture results in the identification of postoperative mediastinitis. Circulation 2003;108:73–8. 10. Yellin A, Refaely Y, Paley M, Simansky D. Major bleeding complicating deep sternal infection after cardiac surgery. J Thorac Cardiovasc Surg 2003;125:554 –8. 11. Flege JB Jr. Pericardial incision for internal mammary artery coronary bypass. Ann Thorac Surg 1987;44:424. 12. Nugent WC, Maislen EL, O’Connor GT, Marrin CAS, Plume SK. Pericardial flap prevents sternal wound complications. Arch Surg 1988;123:636 –9. 13. Shumacker HB, Mandelbaum I. Continuous antibiotic irrigation in the treatment of infection. Arch Surg 1963;86:384 –7. 14. Francel TJ, Kouchoukos NT. A rational approach to wound
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difficulties after sternotomy: reconstruction and long-term results. Ann Thorac Surg 2001;72:1419 –29. Obdeijn MC, de Lange MY, Lichtendahl DHE, de Boer WJ. Vacuum-assisted closure in the treatment of poststernotomy mediastinitis. Ann Thorac Surg 1999;68:2358 –60. Domkowski PW, Smith ML, Gonyon DL Jr, et al. Evaluation of vacuum-assisted closure in the treatment of poststernotomy mediastinitis. J Thorac Cardiovasc Surg 2003;126:386 – 90. Catarino PA, Chamberlain MH, Wright NC, et al. Highpressure suction drainage via a polyurethane foam in the management of poststernotomy mediastinstinitis. Ann Thorac Surg 2000;70:1891–5. Fleck TM, Fleck M, Moidl R, et al. The vacuum-assisted closure system for the treatment of deep sternal wound infections after cardiac surgery. Ann Thorac Surg 2002;74: 1596 –600. Luckraz H, Murphy F, Bryants S, Charman SC, Ritchie AJ. Vacuum-assisted closure as a treatment modality for infections after cardiac surgery. J Thorac Cardiovasc Surg 2003; 125:301–5. Abu-Omar Y, Naik MJ, Catarino PA, Ratnatunga C. Right ventricular rupture during use of high-pressure suction drainage in the management of poststernotomy mediastinitis. Ann Thorac Surg 2003;76:974. Francel TJ. Invited commentary. Ann Thorac Surg 2002;74: 1600.
DISCUSSION DR RICHARD L. PRAGER (Ann Arbor, MI): Dr Merrill, thank you for taking us back to the future because I think that is what you have done. I rise to commend you for reminding us about wound healing and would care because I think that is an essential part of this and I think you have really discussed that in exemplary fashion, as well as in the text, reconvincing us that this is most often a clinical diagnosis, not a computerized tomography scan diagnosis. I have three brief questions. First, are you really content reclosing the sternum and putting drainage systems in those patients who have extensive ascending or transverse aortic reconstruction with graft material? Second, it is my sense that these irrigation systems are not really soaker hoses, but they are just 7 days of a parallel tract that only irrigates the tract and therefore do not truly irrigate the mediastinum. I would like your thoughts about these two issues. And finally, is there anyone that you would actually flap as the primary procedure? I enjoyed the paper very much. Thanks, Dr Merrill. DR MERRILL: I will answer your questions as well as I can. Thank you for being so kind in your comments. Fortunately, we have not experienced instances of deep mediastinal infection involving bypass grafts or grafts in the aorta, cannulation sites, etcetera. This is perhaps due in part to the fairly routine use of a pericardial flap to cover over the anterior surface of the heart prior to closing the sternum at the time of the primary procedure. This is a strategy that was proposed by my colleague, Dr Flege, a number of years ago, and we think that perhaps this has helped prevent these deep infections. So for the most part we have felt content in closing the wound as described in the presentation. If there is no evidence of a space problem at the time of the operation for mediastinitis we have used the technique described. However, if we did encounter a situation in which there was mediastinal scarring or a deep space problem that might persist, then we would consider an alternative technique.
DR WALTER G. WOLFE (Durham, NC): I enjoyed going back to the future again, as you said. I think this is appropriate if you have a bone that you can put back together. I would like to know what you do with the brisket sternum. What were the white counts in these patients, how many had positive blood cultures, and what were the culture results from your wounds, because in our experience most of the time the bone can’t be reapproximated and you are left with needing living tissue to fill that space? So I just wonder, it seems like you had an unusual group of patients. At least the ones who are referred in to us, most of the time you have positive blood cultures and a brisket sternum. The Wound-Vac we feel is the most important part of the early management, but still, if you can’t put the bone back together, which in our experience is the majority of the cases, I think your group is kind of skewed here to the right or the left of center, whichever side you want to go to. I appreciate your comments. DR MERRILL: Thank you for your remarks. Clearly you have raised several really important points. The key, I think, in achieving success with this or any technique is careful and stable reapproximation of the tissues, particularly the sternum, in order to help facilitate wound healing. Several times I have shared great concern with my colleagues in approaching these patients when the sternum seemed to be quite soft, and we were very worried whether or not we would be able to achieve healing. However, after taking adequate time to work on the sternum with rongeurs, curettes or shaving off the edges with a saw, we are usually left with enough sternum to bring together. We postulate that a lot of wires placed and tightened very carefully will bring the edges back together and achieve stability satisfactorily in most cases. I did not mention white blood cell counts in the presentation, but routinely these patients have leukocytosis. Many of them have positive blood cultures at the time of operation, as well as positive cultures from the mediastinum.