**2. Incidence and risk factors of Deep Sternal Wound Infection (DSWI)**

Infection involving the sternal bones and/or retrosternal space is a serious complication of median sternotomy. Although, DSWI can be described from many perspectives, the definition according to the Center for Disease Control and Prevention (CDC), is used for distinguishing DSWI from others types of sternal wound infections (SWIs), and is respected by most authors (Table 1) [5]. Looking through the incidence of DSWI ranging between 0.3 to 3.2%, no consid‐ erable changes have been observed in the incidence of DSWI over the last 30 years [6-22]. It could be perceived that the numerous advances in cardiac surgery, post-operative care and employment of preventive measurements may have played a role in reducing the incidence of DSWI in the last 10 years. Today surgically treated patients' cohorts are different than patients operated on 20 years ago in terms of advanced age, co-morbidities, and surgical

complexity. In other words, the relatively steady status of DSWI incidence over the last three decades might be considered a satisfactory result [23]. Recently Matros et al showed from a large single institution experience with 21,000 sternotomies a reduction in the incidence of DSWI from 1.57 to 0.88% in the last 15 years. They concluded that the rate of DSWI was significantly diminished particularly in the diabetic population, from 3.2% to 1.0%, related to tight glycemic control [19].

factors traditionally associated with an increased risk of DSWI are inconsistently seen in analyses of retrospective studies including advanced age, emergency surgery, hemodynamic instability, low ejection fraction, duration of surgery and CPB time, and renal failure [6-22]. Incidence and risk factors based on multivariable analysis from larger retrospective studies

Current Challenges in the Treatment of Deep Sternal Wound Infection Following Cardiac Surgery

**DSWI incidence**

1996 1830 NA Obesity, BIMA, hemodynamic instability, re-

do surgery

+diabetes/CHF

BIMA

ventilation

Loop FD et al [6] 1985-1987 6504 1.1% Obesity, BIMA+diabetes, time of operation, Milano CA et al [7] 1987-1995 6459 1.3% Obesity, CHF, re-do surgery, CPB time

Hollenbeak et al [11] 1996-1998 1519 2.7% Obesity, renal inssuficieny, re-exploration Filsouri et al [12] 1998-2005 5798 1.80% Obesity, MI, diabetes, COPD, CPB time, re-

Toumpoulis et al [14] 1992-2002 3760 1.1% Diabetes,dialysis, hemodynamic instability,

Risnes et al [15] 1989-2000 18532 0.6% Age, male gender, obesity, COPD, diabetes Crabtree et al [16] 1996-2003 4004 2.2% Obesity, diabetes,"/>2 transfusion units Fowler et al [17] 2002-2003 331429 NA Obesity, diabetes, MI, urgent surgery Sjoegren et al [18] 1999-2004 4781 0.95% Diabetes, obesity, low EF, renal failure

Tang et al [13] 1990-2003 30102 0.77% Age, diabetes, stroke, CHF, BIMA

Matros et al [19] 1991-2006 21000 1.35% Prolonged CPB time

Upton et al [21] 1998-2003 5176 1.2% Diabetes, urgent surgery, low EF Sachithanandan et al [22] 2001-2005 4586 1.65% Diabetes, smoking, age, prolonged

De Feo et al [20] 1979-2009 22366 0.89% NA

**Independent risk factors**

http://dx.doi.org/10.5772/55310

495

exploration, prolonged ventilation

**No. of patients**

Braxton et al [8] 1992-1996 15406 1.25% Obesity, low EF, COPD

Eklund et al [9] 1990-1999 10713 1.1% Obesity, BMI

are summarized in Table 2.

The Parisian Mediastinitis Study Group [10]

NA - not adrressed

EF - ejection fraction

BIMA - bilateral IMA harvesting

CHF - congestive heart failure MI - myocardial infaction

COPD - chronic obstructive pulmonary disease

**Table 2.** Analyses of incidence and risk factors of DSWI

**Authors Patients´**

**enrollement**


**Table 1.** Center for Disease Control and Prevention (CDC) criteria of DSWI (modified from Mangan et al[5])

The identification of risk factors for the development of DSWI is crucial in the effort to reduce the risk of infection [6-22]. Although more than two dozen factors were obtained for uni-, and multivariable analyses, only obesity and diabetes mellitus were constantly proven in publish‐ ed studies [6-18,21,22]. Obesity is a strong risk factor for development of DSWI. Even though BMI does not correlate closely with body fat, there is a step-wise relationship between BMI and the risk of major surgical infection in cardiac surgery [7,15,24]. It is caused not only through technical obesity-related problems, but also through less effective penetration of antibiotics into the fat tissue [24]. Undoubtedly, diabetics are at a higher risk of developing DSWI, making the role of perioperative glycemic control crucial. Unsatisfactory preoperative glycemic control is considered to be an important risk factor for development of DSWI [25,26]. Internal mam‐ mary artery (IMA) harvesting, particularly in the pedicled fashion, has been found to have a higher incidence of DSWI in a CABG cohort compared with valvular procedures [7,8]. Furthermore, this risk becomes stronger when both IMA are used for revascularization or in the diabetic population, but this effect might be attenuated when both IMA are taken down in a skeletonized fashion, even in diabetics [10,27,28]. Chronic obstructive pulmonary disease (COPD) or smoking increases the risk of infectious complications, prolonged post-operative ventilation, and jeopardizes sternal stability from excessive coughing [6,12,15]. Data address‐ ing the impact of early tracheostomy on DSWI incidence is conflicting [29-31]. Historically, a strong relationship between early tracheostomy and DSWI has not been confirmed; but tracheostomy is known to reduce the need for mechanical ventilation and thereby may limit risk of pulmonary infection and ICU stay [32]. Furthermore, re-exploration for bleeding has been analyzed as an independent risk factor for DSWI in several studies [11,12]. The compo‐ nents of this risk factor include the risk of iatrogenic bacteriological wound contamination within the inherent re-exposure, the deleterious effect of anemia and/or concomitant hemo‐ dynamic instability, and the amount of given allogenic blood transfusion units [10,33]. Other factors traditionally associated with an increased risk of DSWI are inconsistently seen in analyses of retrospective studies including advanced age, emergency surgery, hemodynamic instability, low ejection fraction, duration of surgery and CPB time, and renal failure [6-22]. Incidence and risk factors based on multivariable analysis from larger retrospective studies are summarized in Table 2.


NA - not adrressed BIMA - bilateral IMA harvesting EF - ejection fraction COPD - chronic obstructive pulmonary disease CHF - congestive heart failure MI - myocardial infaction

complexity. In other words, the relatively steady status of DSWI incidence over the last three decades might be considered a satisfactory result [23]. Recently Matros et al showed from a large single institution experience with 21,000 sternotomies a reduction in the incidence of DSWI from 1.57 to 0.88% in the last 15 years. They concluded that the rate of DSWI was significantly diminished particularly in the diabetic population, from 3.2% to 1.0%, related to

tight glycemic control [19].

494 Artery Bypass

**Diagnosis of DSWI requires at least one of the following criteria:** (1) anorganism is isolated from culture of mediastinal tissue or fluid

and there is either purulent drainage from the mediastinum

(2) evidence of mediastinitis is seen during operation or byhistopathological examination

or an organism isolated from blood culture or culture of drainage of the mediastinal area

**Table 1.** Center for Disease Control and Prevention (CDC) criteria of DSWI (modified from Mangan et al[5])

The identification of risk factors for the development of DSWI is crucial in the effort to reduce the risk of infection [6-22]. Although more than two dozen factors were obtained for uni-, and multivariable analyses, only obesity and diabetes mellitus were constantly proven in publish‐ ed studies [6-18,21,22]. Obesity is a strong risk factor for development of DSWI. Even though BMI does not correlate closely with body fat, there is a step-wise relationship between BMI and the risk of major surgical infection in cardiac surgery [7,15,24]. It is caused not only through technical obesity-related problems, but also through less effective penetration of antibiotics into the fat tissue [24]. Undoubtedly, diabetics are at a higher risk of developing DSWI, making the role of perioperative glycemic control crucial. Unsatisfactory preoperative glycemic control is considered to be an important risk factor for development of DSWI [25,26]. Internal mam‐ mary artery (IMA) harvesting, particularly in the pedicled fashion, has been found to have a higher incidence of DSWI in a CABG cohort compared with valvular procedures [7,8]. Furthermore, this risk becomes stronger when both IMA are used for revascularization or in the diabetic population, but this effect might be attenuated when both IMA are taken down in a skeletonized fashion, even in diabetics [10,27,28]. Chronic obstructive pulmonary disease (COPD) or smoking increases the risk of infectious complications, prolonged post-operative ventilation, and jeopardizes sternal stability from excessive coughing [6,12,15]. Data address‐ ing the impact of early tracheostomy on DSWI incidence is conflicting [29-31]. Historically, a strong relationship between early tracheostomy and DSWI has not been confirmed; but tracheostomy is known to reduce the need for mechanical ventilation and thereby may limit risk of pulmonary infection and ICU stay [32]. Furthermore, re-exploration for bleeding has been analyzed as an independent risk factor for DSWI in several studies [11,12]. The compo‐ nents of this risk factor include the risk of iatrogenic bacteriological wound contamination within the inherent re-exposure, the deleterious effect of anemia and/or concomitant hemo‐ dynamic instability, and the amount of given allogenic blood transfusion units [10,33]. Other

(3) one of the following, fever("/>38º C), chest pain, or sternal instability, is present

**Table 2.** Analyses of incidence and risk factors of DSWI
