CLINICAL ISSUES

Risk factors for deep sternal wound infections after cardiac surgery in

Jordan

Ibtisam M Al-Zaru, Ali A Ammouri, Mousa A Al-Hassan and Anas A Amr

Aim. The purpose of this study was to assess rates of and risk factors for deep sternal wound infection after coronary artery

bypass grafting surgery.

Background. Deep sternal wound infection is one of the most devastating complications of cardiac surgery, resulting in multiple

operative and non-operative procedures and increased hospital costs.

Design. A retrospective design using an existing coronary artery surgery database of adults (n = 206) who had undergone

coronary artery bypass grafting surgeries between January 2004–January 2006 at a university affiliated hospital, northern

Jordan was used.

Method. Multiple logistic regression analyses were used to asses rates of and risk factors for deep sternal wound infection.

Results. Deep sternal wound infection incidence rate was 22% of the total sample. Risk factors of deep sternal wound infection

include: (1) diabetes (OR = 0Æ317, p = 0Æ048), (2) Obesity (OR = 0Æ275, p = 0Æ011), (3) duration of surgery (OR = 4Æ22,

p = 0Æ032) and (4) use of intraaortic balloon pump (OR = 0Æ033, p = 0Æ001).

Conclusion. The proposed model provides a preliminary indication of risk factors placing coronary artery bypass grafting

patients at risk of DSWI. Further investigations and testing of the model are needed.

Relevance to clinical practice. Determining patients who are at risk of developing deep sternal wound infection after cardiac

surgeries is the first step towards its prevention.

Key words: coronary artery bypass grafting, deep sternal wound infection, infection, Jordan, risk, wounds

Accepted for publication: 15 July 2009

Introduction

Coronary heart disease (CHD) remains the leading cause of

death in developing and developed countries (World Health

Organization 2006). In Jordan, 30,491 patients of coronary

artery diseases were reported in the year 2005 and they were

responsible for 38% of the main causes of mortality (Jordan

Ministry of Health [MOH] 2005, CDC 2006). Coronary

artery bypass grafting (CABG) was considered one of the

major surgical procedures used to alleviate symptoms of

CHD. In Jordan, the number of CABG surgeries has

dramatically increased since 1990; with 3000 cardiac surger-

ies annually (MOH 2005). Although CABG surgery has great

advantages of minimising morbidity and mortality, it poses a

great threat to life and future health (Borger et al. 1998,

Orenstein et al. 2005).

One of the major complications after CABG surgery is

deep sternal wound infection (DSWI) which is an infection of

the anterior mediastinal space involving muscle, bone and/or

mediastinum (Garner et al. 1988). The documented incidence

Authors: Ibtisam M Al-Zaru, PhD, RN, Assistant Professor, Faculty

of Nursing, Jordan University of Science & Technology, Irbid; Ali A

Ammouri, PhD, RN, MSN, Assistant Professor, School of Nursing,

Hashemite University, Zarqa; Mousa A Al-Hassan, PhD, RN,

Associate Professor, Faculty of Nursing, Jordan University of

Science & Technology, Irbid; Anas A Amr, RN, MSN, Registered

Nurse, King Abdullah University Hospital, Irbid, Jordan

Correspondence: Ali Ammouri, Assistant Professor, School of

Nursing, Hashemite University, PO Box 150459, Zarqa 13115,

Jordan. Telephone: 962 5 3903333 ext. 4621.

E-mail: aliammouri@yahoo.com, aammouri@hu.edu.jo

� 2010 Blackwell Publishing Ltd, Journal of Clinical Nursing, 19, 1873–1881 1873

doi: 10.1111/j.1365-2702.2010.03193.x

of DSWI varies from 0Æ6–3% (Vaska 1993, Borger et al.

1998, Baskett et al. 1999, Olsen et al. 2002). DSWI is one of

the most devastating complications of cardiac surgery,

resulting in multiple operative and non-operative procedures

and increased hospital costs with some patients requiring

hospitalisation as long as six months (Hollenbeak et al.

2000, Orenstein et al. 2005). The result of this complication

is a mortality of 8Æ6–47% (De Feo et al. 2001, Olsen et al.

2002). Therefore, understanding of risk factors of DSWI

post-CABG may provide information to alert nurses to

patients who are at risk and optimise the preoperative health

status of CABG patients.

Background

Many risk factors have been identified as independent predic-

tors for DSWI following CABG, which include preoperative

risk factors (e.g., age, gender, obesity, smoking,, chronic

obstructive pulmonary disease (COPD), hypertension, diabe-

tes mellitus and emergency cardiac surgery); intraoperative

risk factors [e.g., use of internal mammary arteries (IMA) and

long duration of surgery and cardiopulmonary bypass (CPB)

time] and postoperative risk factors (e.g., prolonged mechan-

ical ventilation, re-exploration for bleeding and haemody-

namically complicated postoperative course) (Troutman et al.

2001, Ku et al. 2005, Toumpoulis et al. 2005).

The sternal wound infection prediction model provided the

framework for this study (Hussey et al. 1998). This regres-

sion model identified preoperative, intraoperative and post-

operative patient characteristics considered as risk factors for

postoperative DSWI. Assessing relationships between presur-

gical patient characteristics and incidence of DSWI may be

important for early intervention and care-related decisions by

nurses as well as other health care providers, patients and

family members.

Preoperative risk factors

Many studies of DSWI following CABG surgery have

attempted to identify preoperative risk factors for infection.

Some risk factors emerge from several studies and are well

documented that include advanced age, male gender, female

gender, obesity, diabetes, COPD, current smoking and urgent

CABG procedure (Borger et al. 1998, Vuorisalo et al. 1998,

McConkey et al. 1999, Sofer et al. 1999, Thomas et al. 1999,

Orhan et al. 2004). Diabetes mellitus has been proven to be

the most independent risk factor for DSWI following open

heart procedures (Swenne 2006). It increases the incidence of

infection up to fivefold over the normal population (Toum-

poulis et al. 2005).

Obesity is often considered to be a significant risk factor

and an independent predictor for the development of post-

operative DSWI (Zacharias & Habib 1996, Cayci et al.

2008). DSWI occurs twice as frequently in obese individuals

and nearly threefold in those who are severely obese

(Birkmeyer et al. 1998). Also, COPD was found to be an

independent risk factor associated with the development of

DSWI. Patients with COPD have greater colonisation of

bacteria that may lead to prolonged ventilator time after

surgery; patients on the ventilator longer than 48 hours had a

9Æ5-fold greater chance of developing deep sternal wound

infection (Baskett et al. 1999, Khan et al. 2000).

Intraoperative risk factors

Researchers found that the incidence of deep sternal wound

infection increased with the use of a single IMA and increased

further with the use of bilateral IMA on patients with

diabetes (De Paulis et al. 2005). In addition, harvesting of a

unilateral IMA caused a decrease in the blood supply to the

chest area, increased duration of surgery and increased

bleeding postoperatively (Sethi et al. 1991, Carrier et al.

1992).

Higher infection rates have been associated with surgical

time longer than four hours; the risk of developing a DSWI

increased 1Æ47-fold for every hour the operation continued

(Kirkland et al. 1999). Extended time on cardiopulmonary

bypass (CPB) is also linked to higher infection rates. The

consequences of CPB increase the likelihood of patients’ need

for blood products, having an extended time on the ventila-

tor, or requiring inotropic support, also increase the risk of

postoperative infection. (Borger et al. 1998, Jaffe & Samm-

uels 1999).

Postoperative risk factors

Patients having postoperative courses complicated by cardiac

arrest with cardiopulmonary resuscitation, bleeding requiring

re-exploration and poor haemodynamics requiring inotropic

support are at increased risk of developing DSWI (Borger

et al. 1998, Khan et al. 2000). Cardiopulmonary resuscita-

tion places the sternum at risk of fracture or dehiscence and

the body diverts blood to vital organs only (Vaska 1993). In

addition, patients requiring re-exploration for bleeding

within the first postoperative days had a 3Æ5- fold higher risk

of a DSWI (Khan et al. 2000). Furthermore, re-exploration

also carries a high likelihood of blood transfusions, inotropic

support, increased length of stay in intensive care unit (ICU)

and ‘ventilation’ time (Milano et al. 1995, Borger et al. 1998,

Baskett et al. 1999). Postoperative length of stay in ICU,

IM Al-Zaru et al.

1874 � 2010 Blackwell Publishing Ltd, Journal of Clinical Nursing, 19, 1873–1881

mechanical ventilator and blood transfusion were found to

have significant effects on development of DSWI (Vaska

1993, Guler et al. 2001, Chelemer et al. 2002, Ku et al.

2005).

Despite the well documented information about risk

factors of DSWI post-cardiac surgery, the literature is lacking

studies that investigated risk factors of DSWI post-CABG

surgery in Jordan. Determining patients who are at risk of

developing DSWI after cardiac surgeries is the first step

towards its prevention. Therefore, the purpose of this study

was to assess prevalence of and risk factors for DSWI after

CABG surgery at a university hospital in northern Jordan.

The objectives of the study were (1) to assess prevalence of

DSWI post-CABG surgeries; (2) to assess risk factors and

their association with DSWI; and (3) to determine predictors

of DSWI post-CABG surgery in Jordan.

Methods

Design

A correlational, retrospective design using an existing coro-

nary artery surgery data base was used to assess prevalence of

and risk factors for DSWI after CABG surgery at a university

hospital in northern Jordan.

Sample and setting

All patients who had undergone CABG surgeries between

January 2005–January 2007 were potential participants in

the current study. Patients were included in this study if they:

(1) had undergone CABG surgery, (2) were between

35–75 years old, (3) were mentally competent and (4) had a

complete medical record. Patients were excluded if they had

any concurrent surgery (e.g., valve replacement, congenital

heart surgery, or carotid endarterectomy) and their surgery

did not require intraoperative cardiopulmonary bypass. The

final sample that met the inclusion criteria was comprised

of 206 subjects.

The study was conducted at a university affiliated hospital,

which is a teaching hospital that offers clinical training for

medical, nursing and other health related specialties and is

located within the campus of a public university. It has a 633

beds capacity with medical, surgical, orthopaedic, emer-

gency, psychiatric, intensive care units, coronary care unit,

catheterisation lab and open heart surgery department. Also,

the hospital is a referral hospital that provides specialised

health care for patients referred from military, governmental

and private hospitals in the northern area of Jordan.

Patients undergoing cardiac surgery are usually admitted a

few days before the surgical procedure for completion of

physical and laboratory examination. Patients with CABG

surgeries usually stay two days in the cardiac intensive care

unit (which has a capacity of four beds and 12 registered

nurses working in the unit) and then if they are stable, are

transferred to the intermediate unit (which has a capacity of

24 beds and 18 registered nurses working in the unit).

Patients stay four to five days in the intermediate unit before

they are discharged home. Annually, around 257 CABG

surgeries are performed at the hospital by four surgeons (King

Abdullah University Hospital 2005). Cases that are diag-

nosed with DSWI during occasional period of stay or

re-admitted for the same reason are treated in the interme-

diate care unit until recovery.

Instrument

The Sternal Wound Infection Prediction Scale (SWIPS)

developed by Hussey et al. (1998) was used to assess risk

factors for DSWI after CABG surgery. The SWIPS was

developed to provide a quick and easy way of assessing

individuals who are at risk of developing DSWI (Hussey

et al. 1998). The tool assesses 21 risk factors in the

preoperative, intraoperative and postoperative phases, with

each factor having a weight of 1–9. A score of 27 or greater

indicates that the patient is at risk of developing DSWI.

Initial data collected retrospectively indicated that the SWIPS

is able to accurately predict patients who will develop a

sternal wound infection with 72% accuracy (Hussey et al.

1998). Troutman et al. (2001) reported sufficient validity

and reliability of the SWIPS with a sensitivity of 60Æ7% (the

percentage of patients with infection predicted to have

infection) and specificity of 75Æ9% (the percentage of

patients without infection predicted not to have infection).

For the purpose of this paper, SWIPS was used only to

identify risk factors for DSWI and total scores were not

calculated; all risk factors were dichotomously scored. In this

study, a special case of alpha coefficient (KR20) was

calculated for the competing demands scale because data

were dichotomously scored; it was 0Æ79. Demographic

characteristics of the subjects were collected by an instru-

ment that was developed by the researchers that include age,

gender, marital status, weight, height and body mass index,

date of operation, length of stay in ICU preoperative and

type of organisms isolated.

Data collection

The study survey and protocol were reviewed and approved

by the Institutional Review Boards at a governmental

university and at a university hospital. Sample selection was

Clinical issues Deep sternal wound infections

� 2010 Blackwell Publishing Ltd, Journal of Clinical Nursing, 19, 1873–1881 1875

derived from the coronary artery surgery data base at the

Medical Records Department (MRD). The researchers col-

lected the data by reviewing all medical records of eligible

patients to complete the Sternal Wound Infection Prediction

Scale (SWIPS). The patient information was entered and

confidentially maintained within the MRD.

A DSWI was defined according to the guidelines of the

CDC ‘as an infection of the anterior mediastinal space

involving muscle, bone and/or mediastinum’ (Garner et al.

1988, p. 129). Diagnosis of DSWI required at least one of the

following criteria: (1) an organism isolated from culture of

mediastinal tissue or fluid; (2) evidence of mediastinitis seen

during surgery; and (3) presence of chest pain, sternal

instability, or fever (>38 �C) and purulent discharge from

the mediastinum area (during 30- days postoperation time)

(King et al. 2002).

Potential risk factors for DSWI were classified into three

groups according to stages (preoperative, intraoperative and

postoperative). Preoperative potential risk factors included

demographic factors (age, gender and smoking), medical

history factors (diabetes, hypertension and COPD) and

physical parameters (ejection fraction, impaired immunity

response (abnormal white blood cells count), emergency

cardiac surgery and obesity body mass index [(BMI) ‡ 30]

(Table 1). Intraoperative potential risk factors included

duration of surgery, use of an intraaortic balloon pump

(IABP), use of an IMA and total cardiopulmonary bypass

time (Table 2). Postoperative potential risk factors included

blood transfusion, inotropic support (dopamine-dobutamine

and other medication such as epinephrine, nor-epinephrine,

amiodarone and neo-synephrine), mechanical ventilation

(number of hours postoperative), cardiopulmonary resusci-

tation (CPR), length of stay in ICU after cardiac surgery and

re-exploration for bleeding (Table 3).

Data analysis

The creation of data analysis files were completed and

managed by the researchers. The data were entered into SPSSSPSS

(Version 12) computer software. Data were organised by

subject’s identification number and no identifiers were used.

All data were analysed at alpha level of 0Æ05.

To meet objective number one, descriptive statistics were

used to describe study variables. Categorical data were

recorded and were reported as frequencies and percentages.

Continuous variables were analysed reporting means and

standard deviation. To meet objective number two, risk

factors for DSWI were assessed using t-test analysis used for

continuous variables and the chi-square test for categorical

variables. In addition, we conducted Fisher’s exact test

whenever the chi-square expected value of at least one cell

was less than five (Tables 1 and 3).

To develop a model to predict risks for DSWI that meet

objective number three, the association among the indepen-

dent variables and the dichotomous dependent variable

(DSWI) was tested using stepwise multiple logistic regres-

sion analysis with a generalised logit link function. The odds

ratio from the model indicated the association of interest.

As there were 21 potential risk factors (see Tables 1–3), to

avoid multicollinearity among the explanatory variables, we

performed collinearity diagnostic by assessing the value of

variance-inflation factor (VIF); variables that has VIF

greater than 10 were excluded from the model analysis

Table 1 Preoperative risk factors for deep sternal wound infection

(n = 206)

Variable

Infected

(n = 44)

Non-infected

(n = 162)

v2 p-value

No. or

mean %

No. or

mean %

Age (years)* 61Æ7 (7Æ72)� 60Æ0 (9Æ43) 0Æ52

Ejection

Fraction*

52Æ9 (10Æ16) 53Æ9 (8Æ54) 0Æ25

Gender

Male 29 65Æ9 132 81Æ5 4Æ92 0Æ027

Female 15 34Æ1 30 18Æ5Smoker

Yes 23 52Æ3 110 67Æ9 3Æ69 0Æ055

No 21 47Æ7 52 32Æ1Diabetes

Yes 30 68Æ2 87 53Æ7 2Æ95 0Æ086

No 14 31Æ8 75 46Æ3Hypertension

Yes 37 84Æ1 128 79Æ0 0Æ56 0Æ454

No 7 15Æ9 34 21Æ0COPD�

Yes 1 2Æ3 4 2Æ5 0Æ006 1Æ00

No 43 97Æ7 158 97Æ5Obesity

BMI ‡ 30 26 59Æ1 58 35Æ8 7Æ77 0Æ005

BMI < 30 18 40Æ9 104 64Æ2Immune

Impairment�

Yes 1 2Æ3 1 0Æ6 0Æ98 0Æ382

No 43 97Æ7 161 99Æ4Emergency

surgery

Yes 4 9Æ1 5 3Æ1 2Æ98 0Æ084

No 40 90Æ9 157 96Æ9

Data are numbers and percentage unless otherwise indicated.

*Assessed by t-test.�Numbers in parentheses, standard deviation.�Fisher’s exact test (expected frequency < 5).

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1876 � 2010 Blackwell Publishing Ltd, Journal of Clinical Nursing, 19, 1873–1881

(Schroeder 1990). All variables were included in the

analysis.

Results

Objective one

Two hundred and six patients with CABG surgeries met the

inclusion criteria and composed the study sample. Of the 206

patients, 161 (78Æ2%) were males and 45 (21Æ8%) were

females. Patients’ ages ranged from 35–75 years with a mean

age of 60Æ3 years (SD 9Æ1). Data revealed that all the subjects

were married, none of them had stayed pre-operatively in the

ICU and only two subjects (1%) had impaired immune

response (See Table 2–4). Approximately 21Æ6% (n = 44)

from total sample developed DSWI, and coagulase-negative

staphylococcus (COAG) bacteria occupied the majority of

infected participants (54Æ5%).

Objective two

Preoperative risk factors

Chi-square analysis indicated that the percentage of males

who had DSWI was significantly higher than the percentage

of females who had DSWI (66Æ9 vs. 34Æ1, v2 = 4Æ92, df = 1,

p = 0Æ027). Also, there was a significant difference in obesity

between DSWI patients and non-infected subjects (v2 = 7Æ77,

df = 1, p = 0Æ005). The percentages of subjects with BMI

‡ 30 were 59Æ1 for DSWI and 35Æ8 for non-infected. How-

ever, there were no significant differences in age, ejection

fraction, smoking, diabetes, hypertension, COPD, immune

response and emergency surgery between DSWI patients and

non-infected subjects (Table 1).

Table 2 Intraoperative risk factors for deep sternal wound infection

(n = 206)

Variable

Infected

(n = 44)

Non-

infected

(n = 162)

v2 p-valueNo. % No. %

Duration of surgery

£4 hours 35 79Æ5 147 90Æ7 4Æ21 0Æ04

>4 hours 9 20Æ5 15 9Æ3IABP*

Yes 17 38Æ6 3 1Æ9 53Æ41 0Æ000

No 27 61Æ4 159 98Æ1CPB time

£2 hours 8 18Æ2 44 27Æ2 1Æ47 0Æ223

>2 hours 36 81Æ8 118 72Æ8IMA

Yes 36 81Æ8 140 86Æ4 0Æ58 0Æ443

No 8 18Æ2 22 13Æ6

IABP, intraaortic balloon pump; CPB, cardiopulmonary bypass;

IMA, internal mammary arteries.*Fisher’s exact test (expected frequency < 5).

Table 3 Postoperative risk factors for deep sternal wound infection

(n = 206)

Variable

Infected

(n = 44)

Non-infected

(n = 162)

v2 p-value

No. or

mean

% No. or

mean

%

Mechanical

ventilation*

13Æ2(9Æ62)�

11Æ8(8Æ23)

0Æ56

Blood transfusion�

Yes 44 100 147 90Æ7 4Æ39 0Æ044

No 0 0 15 9Æ3Dopamine-dobutamine

Yes 32 72Æ7 47 29Æ0 27Æ96 0Æ001

No 12 27Æ3 115 71Æ0Other medication

Yes 15 34Æ1 18 11Æ1 13Æ58 0Æ001

No 29 65Æ9 144 88Æ9CPR�

Yes 3 6Æ8 0Æ0 0Æ0 11Æ21 0Æ009

No 41 93Æ2 162 100

Stay in ICU

£3 days 20 45Æ5 125 77Æ2 16Æ68 0Æ001

>3 days 24 54Æ5 37 22Æ8Re-exploration

Yes 16 36Æ4 18 8Æ0 22Æ97 0Æ001

No 28 63Æ6 149 92Æ0

Data are numbers and percentage unless otherwise indicated.

Other medication, epinephrine, nor-epinephrine, amiodarone, &

neo-synephrine; CPR, cardiopulmonary resuscitation; ICU, intensive

care unit.

*Assessed by t-test.�Numbers in parentheses, standard deviation.�Fisher’s exact test (expected frequency < 5).

Table 4 Final fitted logistic regression model for risk factors for deep

sternal wound infection (n = 206)

Variable Beta estimate p-value OR 95% CI

Intercept 25Æ11 0Æ000

Diabetes �1Æ149 0Æ048 0Æ317 0Æ099–0Æ933

Obesity

(BMI ‡ 30)

�1Æ252 0Æ011 0Æ275 0Æ102–0Æ742

Duration of

surgery

(>4 hours)

1Æ440 0Æ032 4Æ220 1Æ136–15Æ677

IABP �3Æ404 0Æ000 0Æ033 0Æ005–0Æ204

All 21 variables were entered in the model.

OR, odds ratio; CI, confidence interval; IABP, intraaortic balloon

pump.

Clinical issues Deep sternal wound infections

� 2010 Blackwell Publishing Ltd, Journal of Clinical Nursing, 19, 1873–1881 1877

Intraoperative risk factors

Chi-square analysis indicated that the duration of surgery

(v2 = 4Æ21, df = 1, p = 0Æ04) and use of IABP (v2 = 53Æ41,

df = 1, p < 0Æ001) showed significant associations with

infection incidences. DSWI patients were more likely than

non-infected patients to have longer duration of surgery

and more use of IABP (See Table 2). The percentage of

patients with DSWI who experienced a duration of surgery

more than four hours was higher than the percentage of

non-infected patients who experienced a duration of sur-

gery more than four hours (20Æ5 vs. 9Æ3). The percentage

of patients with DSWI who had used IABP was higher

than the percentage of non-infected patients who had used

IABP (38Æ6 vs. 1Æ9). However, there were no significant

differences in use of an IMA and cardiopulmonary bypass

time.

Postoperative risk factors

Chi-square analysis indicated that blood transfusion

(v2 =4Æ39, df = 1, p = 0Æ044), dopamine-dobutamine use

(v2 = 27Æ96, df = 1, p = 0Æ001), other medication use (v2 =

13Æ58, df = 1, p < 0Æ001), CPR (v2 = 11Æ21, df = 1,

p = 0Æ009), stay in ICU (v2 = 16Æ68, df = 1, p = 0Æ001) and

re-exploration (v2 = 22Æ97, df = 1, p = 0Æ001) showed sig-

nificant differences among DSWI patients and non-infected

patients (See Table 3). However, there was no significant

difference in mechanical ventilation mean time between

DSWI patient and non-infected patients.

Objective three

Generalised logit model

Statistics suggested that the model fit the data well

(Chi-square = 87Æ57, p < 0Æ001; Goodness of fit = 5Æ738,

p = 0Æ677). A probability (p) value >0Æ05 for Hosmer and

Lemeshow goodness of fit and the deviance residual

measures indicate that the model fits the data well. The

final model derived from the entire sample (N = 206) was

composed of the following variables: (1) diabetes (OR = 0

Æ317, p = 0Æ048), (2) Obesity (OR = 0Æ275, p = 0Æ011), (3)

duration of surgery (OR = 4Æ22, p = 0Æ032) and (4) use of

IABP (OR = 0Æ033, p < 0Æ001) (Table 4). Diabetic patients

had 31% higher risk of DSWI than non-diabetic patient;

patients with BMI ‡ 30 had 27 per cent higher risk of

DSWI than patients with BMI £ 30; compared with

patients with duration of surgery £4 hours, patients who

had duration of surgery >4 hours had 4Æ2 times the

risk of DSWI; and patients who used IABP post-surgery

had 3 per cent higher risk of DSWI than patients who did

not.

Discussion

The aim of this study was to assess prevalence of and risk

factors for DSWI after CABG surgery at a public university

hospital, northern Jordan. Identifying risk factors for devel-

oping DSWI is important and amenable to early presurgical

intervention by nurses and other health team professionals.

The final model identified diabetes, obesity, duration of

surgery and use of IABP as predictors of DSWI after CABG

surgery.

Twenty-two per cent of the sampled patients reported

significantly high prevalence of DSWI post-CABG surgery.

This result was higher than the globally reported incidence

rate (1–3%) (Borger et al. 1998, Baskett et al. 1999, Olsen

et al. 2002).

Data revealed that COAG accounted for up to 54Æ5% of

DSWI which is congruent with what the literature reported

(Antunes et al. 1997, Catarina et al. 2000). COAG were a

normal flora occupying the patient’s own skin and the

surgical team’s nose, arms and foreheads (Catarina et al.

2000). Skin preparation (clipping instead of shaving) and

applying strict universal precaution such as wearing gloves,

head cap, face mask and gown is necessary to prevent

microbes’ spread. Also, adherence to aseptic technique and

using separate instruments for each surgical site is a must

(Catarina et al. 2000).

Chi-square analysis indicated that CABG patients with

DSWI were males, obese, had long surgery duration, used

IABP and had postoperative courses complicated by CPR,

bleeding requiring re-exploration and blood transfusion and

poor haemodynamics requiring inotropic medication sup-

port that resulted in an increased length of stay in ICU

postoperatively. All these factors placed CABG patient at

risk of having DSWI. These results are consistent with the

findings of previous studies (Borger et al. 1998, Khan et al.

2000).

The final model was constructed from 21 risk factors using

stepwise multiple logistic regression analysis with a general-

ised logit link function for the dichotomous dependent

variable. Four variables emerged as risk factors for DSWI,

two preoperative parameters related to patient history or

physical characteristics (diabetes and obesity), one intraop-

erative parameter related to duration of surgery and one

postoperative parameter related to use of IABP were risk

factors for DSWI. The results of this study support findings

from previous reports that diabetes (Toumpoulis et al. 2005,

Swenne 2006), obesity (BMI ‡ 30) (Borger et al. 1998,

McConkey et al. 1999, Cayci et al. 2008), long surgery

duration (Kirkland et al. 1999) and the use of IABP (Borger

et al. 1998) are predictors of DSWI.

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1878 � 2010 Blackwell Publishing Ltd, Journal of Clinical Nursing, 19, 1873–1881

Previous studies explained that the effects of diabetes on

the vasculature may predispose individuals to infection and

may impede the ability to treat the infection because of poor

blood supply to the infected area and the inability of

antibiotics to reach the site, in addition to impairment of

the white blood cells’ ability to phagocytose and effectively

kill bacteria (Zerr et al. 1997). Furnary et al. (1999) sug-

gested that a continuous intravenous insulin infusion pre and

postoperatively reduced the incidence of DSWI.

Patients with obesity have more adipose tissue in the chest

area that is poorly perfused, which limits oxygen delivery.

Furthermore, the extra weight caused by adipose tissue puts

additional strain on the incision, which may further reduce

blood supply (Vaska 1993). Obese individuals are also at risk

for sternal wound dehiscence and sternal wire breakage

(Shaffer & Corish 1998). Planned cardiac surgery prepara-

tion must take into consideration controlling patients’ weight

with strategies that are suitable for the health status of the

patient and availability of time.

Duration of surgery was found to be a risk factor for

DSWI. The longer the duration of surgery the more environ-

mental exposure and therefore a higher infection rate was

expected. Factors related to duration of surgery included

patient disease severity, urgency of surgery, surgical proce-

dure, surgical team and operating room The study findings

suggest that the operating room environment (e.g., temper-

ature, humidity and airflow), urgency of surgery, surgical

procedure and surgical team should be examined for other

risk factors for DSWI.

Use of IABP was found to be a risk factor for DSWI. The

IABP is a circulatory support device. Patients who need an

IABP are those suspected of having severe left ventricular

dysfunction or congestive heart failure. While one can

reasonably assume that the most severely ill patient – who

required IABP- also experienced prolong surgery duration,

prolonged mechanical ventilation, complicated postoperative

course haemodynamically, use of inotropic support and

prolonged stay in ICU, it is unclear which factors are

contributing to the relation between use of IABP and

development of DSWI. The study findings suggested that

patient clinical status should be examined further in associ-

ation with DSWI.

Limitations of the study

The results of our study should be interpreted by taking

into account some limitations. The retrospective nature of

this study precluded the ability to infer causal relationships

between the statistically significant risk factors and DSWI.

Therefore, future testing of the proposed model with

prospective longitudinal data will increase understanding

of the most effective predictive model to prevent DSWI

after CABG surgery in Jordan. Small sample size and

convenience sampling and may not be truly representative

of Jordanian CABG patients, thus limiting the generalis-

ability of findings. Important factors that may contribute to

infection include those related to environment, operating

room, surgical and health team and postoperative care

were not included in this study. Further studies might focus

on the relationship between these factors and development

of DSWI.

Conclusion

Assessing presurgical risk factors for DSWI in patients who

will undergo CABG may be important for early intervention

and care-related decisions by nurses as well as other health

care providers, patients and family members. We studied

infection prevalence and risk factors for DSWI post-CABG

at a governmental university hospital in northern Jordan.

High prevalence of DSWI was reported from the sampled

patients. The final model indicated that diabetes, obesity,

duration of surgery and use of IABP were risk factors for

DSWI. Controlling these factors may help in controlling

DSWI after CABG surgery. This explanatory model requires

further development and validation prior to implementation.

Relevance to clinical practice

DSWI is one of the major complications after CABG surgery

DSWI, resulting in multiple operative and non-operative

procedures and increased hospital costs. Identifying risk

factors for developing DSWI is important and amenable to

early presurgical intervention by nurses and other health team

professionals.

Contributions

Study design: IA, AA, MA; data collection and analysis: IA,

AA, MA and manuscript preparation: AA, IA, MA, A Am.

Conflict of interest

The authors declare that they have no conflict of interests.

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