Doi/10.1016_j.ejcts.2009.10.005

Economic aspects of deep sternal wound infections
Karolin Graf, Ella Ott, Ralf-Peter Vonberg, Christian Kuehn, Axel Haverich and Iris Eur J Cardiothorac Surg 2010;37:893-896 This information is current as of January 1, 2012
The online version of this article, along with updated information and services, is http://ejcts.ctsnetjournals.org/cgi/content/full/37/4/893 The European Journal of Cardio-thoracic Surgery is the official Journal of the European Association for Cardio-thoracic Surgery and the European Society of Thoracic Surgeons. Copyright 2010 by European Association for Cardio-Thoracic Surgery. Published by Elsevier. All rights reserved. PrintISSN: 1010-7940. European Journal of Cardio-thoracic Surgery 37 (2010) 893—896 Economic aspects of deep sternal wound infections§ Karolin Graf a,*, Ella Ott a, Ralf-Peter Vonberg a, Christian Kuehn b, a Institute for Medical Microbiology and Hospital Epidemiology, Hannover Medical School, Carl-Neuberg-Str. 1, D-30625 Hannover, Germany b Department for Cardiac, Thoracic, Transplant and Vascular Surgery, Hannover Medical School, Hannover, Germany Received 18 August 2009; received in revised form 7 October 2009; accepted 8 October 2009; Available online 6 November 2009 Objectives: Surgical-site infections are a very expensive complication in cardiac surgery. Thus, the total costs for coronary artery bypass grafting (CABG) surgery may substantially increase when a deep sternal wound infection (DSWI) occurs. This may be due to an extended length ofstay (LOS), the need for additional surgical procedures, vacuum-assisted wound dressing and antibiotic therapy. This study compares the LOS inthe hospital and on an intensive care unit (ICU) as well as the total costs for patients undergoing CABG depending upon the occurrence of asubsequent DSWI. Methods: A case—control study was performed. Total costs of DSWI cases were analysed and compared to patients undergoingCABG without DSWI. Inclusion criterion for cases was the development of a DSWI according to the CDC criteria during hospital stay after CABG. Twocontrol patients without any signs or symptoms of an infection during hospital stay were matched to each case by (1) type of surgery according totheir diagnosis-related group (DRG), (2) age Æ5 years, (3) gender and (4) duration of preoperative hospital stay Æ2 days, but at least as long as thetime at risk of cases before infection. Results: Between January 2006 and March 2008, 17 CABG patients with DSWI (cases) and 34 matchedcontrols were included. The median overall costs of a CABG case were 36,261 Euro compared with 13,356 Euro per control patient withoutinfection ( p < 0.0001). The median overall LOS was 34.4 days versus 16.5 days, respectively ( p = 0.0006). The median LOS on ICU was 6.3 daysversus 5.3 days (no significant difference). Conclusion: DSWI represents an important economic factor for the hospital as they may almost triplethe costs for patients undergoing CABG. Thus, appropriate infection control measures for the prevention of DSWI should be enforced.
# 2009 European Association for Cardio-Thoracic Surgery. Published by Elsevier B.V. All rights reserved.
Keywords: Coronary artery bypass; Length of stay; Reimbursement; Costs Deep sternal wound infection (DSWI) is a devastating complication following cardiac surgery and is associated withsignificant increases in hospital length of stay (LOS), costs, This study was conducted at the department of cardiac, morbidity, and mortality [1,2]. Previous studies have thoracic, transplantation and vascular surgery of the reported DSWI rates from 0.5% to 3.6% [3—5]. Mortality Hannover Medical School, a German tertiary care university rates may vary between 15% and 40% [3,5]. Only few studies hospital. Approximately 2300 patients undergo median have yet described the exact economic impact of DSWI, sternotomy per year in this department for various reasons.
comparing patients with same characteristics and, to the The investigation period included 27 months (January 2006 best of our knowledge, no study did that for the German until March 2008). Prospective surveillance of DSWI was performed during the entire study period by trained The aim of the present study was to calculate the costs of infection control personnel. The frequency of the occur- DSWI after coronary artery bypass grafting (CABG) surgery via rence of DSWI ranged from 1.8% to 3.6% in this time frame Patients were included as cases if they developed a DSWI § Part of this study was presented at the 19th European Congress of Clinical according to the criteria as defined by the Centers for Disease Microbiology and Infectious Diseases (ECCMID) Helsinki, Finland, 2009.
Control and Prevention (CDC) [8] during the hospital stay * Corresponding author. Tel.: +49 511 532 8675; fax: +49 511 532 8174.
E-mail address: Graf.Karolin@MH-Hannover.DE (K. Graf).
1010-7940/$ — see front matter # 2009 European Association for Cardio-Thoracic Surgery. Published by Elsevier B.V. All rights reserved.
doi:10.1016/j.ejcts.2009.10.005 K. Graf et al. / European Journal of Cardio-thoracic Surgery 37 (2010) 893—896 (14) LOS on an intensive care unit and (15) total hospital LOS.
The following demographic data and risk factors were The CDC criteria for a deep incisional infection (class A2) recorded for each patient: (1) age, (2) gender, (3) BMI, (4) was defined by involving tissues beneath the subcutaneous type of surgical procedure, (5) diabetes mellitus, (6) chronic tissue including one of the following findings: purulent obstructive lung disease (COLD), (7) renal insufficiency, (8) drainage from the deep layer, surgical revision or dehiscence nicotine abuse, (9) immune suppression of any kind, (10) on the background of fever, localised pain, or tenderness, and hospital length of stay (LOS) before surgery, (11) ASA score, an abscess or other observable evidence of infection on (12) wound contamination class, (13) date of operation, (14) direct examination, histopathology and radiology. The duration of the procedure, (15) ECC time, (16) appropriate criteria for an organ/space infection (mediastinitis, class application of an antibiotic prophylaxis using a third- A3) include purulent drainage, positive microbiology and an generation cephalosporin, (17) preoperative, intraoperative abscess or other observable evidence of infection.
and postoperative blood glucose levels, (18) extubation time, Patients with sterile dehiscence or superficial sternal (19) LOS on an intensive care unit (ICU) and (20) the overall wound infections were excluded from the study. Re-admitted patients were not eligible as case patients.
Control patients after CABG and without DSWI were matched to DSWI cases in a ratio of 2:1. The followingmatching criteria were applied: (1) age Æ5 years, (2) gender, During the study period, a total of 4130 cardiac surgical (3) identical diagnosis-related group (DRG) in the same year procedures were performed. A total of 120 patients with (= adjusting for underlying disease and reimbursement DSWI were detected by surveillance; 100 (83%) of these were conditions), (4) preoperative LOS Æ2 days (adjusting for diagnosed during their hospital stay in our facility already or time at risk before surgery) and (5) LOS after the thoracic during their subsequent stay in a rehabilitation clinic. The surgical procedure of controls needed to be at least as long as remaining 20 (17%) patients were diagnosed when re- that of cases before the onset of DSWI (= adjusting for time at admitted to our hospital. In total, 27 (23%) events of DSWI occurred after discharge of the patient. Causative micro-organisms were cultured in specimens from 112 (93%) sites of clinical DSWI. The most frequently cultured isolates werecoagulase-negative staphylococci (39%), Staphylococcus Data on the costs for the hospital and reimbursement from aureus (23%; with a proportion of 52% MRSA) and enterococci the health insurance companies for DSWI cases and control (10%). Up to four different microorganisms were detected in patients were provided by the financial controlling depart- a single DSWI site. The mean time after surgery until the ment of our facility. The actual costs of surgery, ICU care, diagnosis of DSWI was 13.4 (median: 19) days.
peripheral ward care, laboratory tests, other costs as well as Usually patients with DSWI are treated by debridement, the reimbursement were calculated for every single case vacuum therapy and sometimes omental reconstruction. All individually. All costs are presented in Euro at the time of matched cases were treated by debridement and vacuum Evaluation of the application of matching criteria was After applying the matching criteria, as described above, done by the Wilcoxon rank-sum test for indent samples.
17 cases and 34 matched controls out of 120 potential control Differences between cases and matched control pairs with patients were included. The total number of patient days of respect to LOS and costs were calculated for the overall cases was 585 days and of controls was 560 days. As shown in hospital LOS, LOS at ICU, LOS after surgery, costs per patientand costs per patient. For all parameters, the medians with a 95% confidence interval (CI95) non-parametric (distribution Costs and length of stay of cases and controls.
free) were calculated. The p-value of differences (cases minus controls) was calculated by the Wilcoxon signed rank test and a p-value <0.05 was considered significant.
We checked for potential risk factors and co-morbidities that may have an influence on the costs and: (1) diabetes mellitus, (2) body mass index (BMI) >25, (3) chronic obstructive pulmonary disease (COPD), (4) renal insuffi- ciency, (5) nicotine abuse, (6) immunosuppression, (7) length of hospital (LOS) stay before surgery, (8) ASA score, (9) woundcontamination class, (10) duration of extra corporal circula- LOS: length of stay; ICU: intensive care unit; 95% CI: 95% confidence interval;n.s.: not significant.
tion (ECC), (11) correct timing of antibiotic prophylaxis, (12) blood glucose levels, (13) duration of mechanical ventilation, * Wilcoxon signed rank test was used.
K. Graf et al. / European Journal of Cardio-thoracic Surgery 37 (2010) 893—896 Difference of costs and reimbursements for deep sternal wound infections incases and control patients.
Financial loss or profit per patient day (s) ward care (13.0%), surgical costs (28.3%), costs for ICU care LOS: length of stay; n.s: not significant; 95% CI: 95% confidence interval.
(29.6%), costs for laboratory tests (16.4%) and other costs * Wilcoxon signed rank test was used.
(12.7%). The median cost of case patients who required DSWItreatment was 36261 Euro, including costs for ward care (24.7%), surgical costs (19.0%), ICU care (27.7%), laboratory Risk factors of all cases and controls.
tests (15.0%) and other costs (13.6%). Costs of cases for the need for treatment that derived from additional admissions are not included in this calculation. The median reimburse-ment from health-care insurance companies was 27,107 Euro per case patient, which means a financial loss of 9154 Euro per patient or 269 Euro per patient day while control patients Preoperative blood glucose level (mmol/l) ended up with a financial profit of 21 Euro per patient day.
Intraoperative blood glucose level (mmol/l) * p-values have been calculated (Wilcoxon rank sum test). LOS, Duration and bypass time showed no significance. Preoperative blood glucose level:p = 0.006, Intraoperative blood glucose level: p = 0.002.
Patients who develop DSWI following cardiac surgery Table 1, the median hospital LOS was twice as long in cases as require longer and more costly care and experience worse in controls (34.4 days vs 16.5 days, p = 0.0006). The median clinical outcomes than patients who do not suffer from this LOS on ICU was also increased for cases but failed to reach complication [2,9,10]. Our data show that at least 1.8% of statistical significance (6.3 days vs 5.3 days). The median patients undergoing open-heart surgery suffered from DSWI.
postoperative LOS was approximately 4 times longer in cases Such a DSWI rate of 1.8% is in line with the earlier reported (32.2 days) than in all controls without infection (8.0 days; rates of 0.5% and 3.2% [4,5]. Inclusion criteria for patients in p = 0.04). In a 30-day follow-up, the mortality rates of the our case—control study are in accordance to the criteria and cases were 17.6% versus 8.8% in controls. Table 2 indicates characteristics as used by others before [11—14].
that, besides the preoperative LOS, the control patients as In our study, patients with sternotomy who developed chosen for our case—control study are a representative DSWI had a doubled mortality rate, a need for 18 additional subgroup of all patients lacking DSWI.
days of LOS and led to much higher costs (s 22,905 in The risk factors and co-morbidities of cases and controls addition) when compared with patients undergoing sternot- omy without developing DSWI. By this our data from aGerman university hospital confirms the previous findings in principle [10]. Because DSWIs are associated with more costlyoutcomes [9], we did not include superficial chest infections Table 5 presents an overview on costs of cases and control.
and leg infections in our cost estimates. This may also explain The median cost of cardiac surgery procedure in control why the estimates of the economic impact of DSWI after patients was 13356 Euro. These costs consisted of costs for cardiac surgery showed to be substantially higher in our studythan in others [8,9]. The main proportion of costs in DSWI case patients was among ward care, costs for additional Co-morbidities of cases and controls.
surgical procedures and costs for prolonged ICU care. The difference in costs between cases and control can be attributed to a shorter hospital LOS of controls, as the proportion of costs for care on peripheral wards were diminished while the proportion of costs for the initial surgical procedure and ICU care are relatively high.
Some limitations have to be kept in mind when interpreting the data presented in our study: (1) As mortality rates were determined by a 30-day follow-up only, we do not know for sure whether all fatal cases were Preoperative MRSA-screening (no. of cases) detected by our surveillance. A longer post-discharge K. Graf et al. / European Journal of Cardio-thoracic Surgery 37 (2010) 893—896 surveillance time frame would be necessary to clarify this tions following coronary artery bypass graft surgery. Chest 2000;118(2): issue. Thus, our data might even underestimate the true [2] Loop FD, Lytle BW, Cosgrove DM, Mahfood S, McHenry MC, Goormastic M, Stewart RW, Golding LA, Taylor PC. J. Maxwell Chamberlain memorial (2) We only included the costs of patients with DSWI that paper. Sternal wound complications after isolated coronary artery bypass derived from their first stay in our hospital but not from re- grafting: early and late mortality, morbidity, and cost of care. Ann Thorac admissions that may have occurred later on. Thus, our data might also even underestimate the true costs due to DSWI.
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Further we cannot say if the prolonged stay after ¨hn C, Gastmeier P, Chaberny IF. Decrease of developing DSWI is caused by the infection only or if deep sternal surgical site infection rates after cardiac surgery by a other co-morbidities may have had an influence.
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[8] Horan TC, Andrus M, Dudeck MA. CDC/NHSN surveillance definition of health care-associated infection and criteria for specific types of infec-tions in the acute care setting. Am J Infect Control 2008;36(5):309—32.
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Economic aspects of deep sternal wound infections
Karolin Graf, Ella Ott, Ralf-Peter Vonberg, Christian Kuehn, Axel Haverich and Iris Eur J Cardiothorac Surg 2010;37:893-896 This information is current as of January 1, 2012
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