Antibiotic prophylaxis in cardiac surgery: systematic review and meta-analysis

Circulating 25-Hydroxyvitamin D and 1,25-Dihydroxyvitamin D Concentrations and Postoperative Infections in Cardiac Surgical Patients: The CALCITOP-Study

BACKGROUND

Vitamin D has immunomodulatory properties and seems to reduce the risk of infections. Whether low vitamin D concentrations are independent risk factors for nosocomial postoperative infections in surgical patients remains to be studied in detail.

METHODS

In 3,340 consecutive cardiac surgical patients, we investigated the association of circulating 25-hydroxyvitamin D (25OHD; indicator of nutritional vitamin D status) and 1,25-dihydroxyvitamin D (1,25[OH]2D; active vitamin D hormone) with nosocomicial infections. The primary endpoint was a composite of thoracic wound infection, sepsis, and broncho-pulmonary infection. Vitamin D status was measured on the last preoperative day. Infections were assessed until discharge. Logistic regression analysis was used to examine the association between vitamin D metabolite concentrations and the composite endpoint.

RESULTS

The primary endpoint was reached by 5.6% (n = 186). In patients who reached and did not reach the endpoint, in-hospital mortality was 13.4% and 1.5%, respectively (P<0.001). Median (IQR) 25OHD and 1,25(OH)2D concentrations were 43. 2 (29.7-61.9) nmol/l and 58.0 (38.5-77.5) pmol/l, respectively. Compared with the highest 1,25(OH)2D quintile (>81.0 pmol/l), the multivariable-adjusted odds ratio of infection was 2.57 (95%CI:1.47-4.49) for the lowest 1,25(OH)2D quintile (<31.5 pmol/l) and 1.85 (95%CI:1.05-3.25) for the second lowest quintile (31.5-49.0 pmol/l). There was no significant association between 25OHD concentrations and the primary endpoint.

CONCLUSIONS

Our data indicate an independent association of low 1,25(OH)2D levels with the risk of postoperative infections in cardiac surgical patients. Future studies should pay more attention on the clinical relevance of circulating 1,25(OH)2D and its regulation.

Gentamicin-Impregnated Collagen Sponge: Effectiveness in Preventing Sternal Wound Infection in High-Risk Cardiac Surgery

Sternal wound infections represent one of the most frequent complications after cardiac surgery and are associated with high postoperative mortality. Several preventive methods have been introduced, and recently, gentamicin-impregnated collagen sponges (GICSs) have shown a promising effect in reducing the incidence of this type of complications. Gentamicin is an aminoglycoside antibiotic that has been widely used to treat infections caused by multiresistant bacteria; despite its effectiveness, its systemic use carries a risk of toxicity. GICSs appear to overcome this side effect, topically delivering high antibiotic concentrations to the wound and thus reducing the toxic-related events. Although several retrospective analyses and randomized controlled trials have studied the use of GICSs in cardiac surgery, conclusions regarding their efficacy in preventing sternal wound infection are inconsistent. We have reviewed the current literature focusing on high-risk patients.

Antimicrobial Formulation and Delivery in the Prevention of Surgical Site Infection

BACKGROUND

A number of adjunct antimicrobial measures have been studied in an attempt to reduce surgical site infection (SSI) rates. In addition to parenteral antibiotic prophylaxis, these measures include oral antibiotics in bowel preparation for colorectal surgery, antiseptic/antimicrobial irrigation, antimicrobial sutures, local antibiotics, skin incision antibacterial sealants, and antimicrobial dressings. It is the purpose of this review to study the evidence behind each of these measures and to evaluate relevant data for recommendations in each area.

METHODS

A systematic review of the literature through PubMed was performed.

RESULTS

Need for adequate dosing and re-dosing of intravenous peri-operative antibiotics, duration of antibiotic usage past wound closure, and the use of antibiotic bowel preparation in colorectal surgery are well defined in the published literature. However, data on local antimicrobial measures remain controversial.

CONCLUSIONS

Proper dosing and re-dosing of prophylactic intravenous antibiotics should become standard practice. Continuation of intravenous antibiotic prophylaxis beyond wound closure is unnecessary in clean cases and remains controversial in clean-contaminated and complex cases. Oral antibiotic bowel preparation is an important adjunct to intravenous antibiotic prophylaxis in colorectal surgery. The use of topical antimicrobial and antiseptic agents such as antibacterial irrigations, local antimicrobial application, antimicrobial-coated sutures, antibacterial wound sealants, and antimicrobial impregnated dressings in the prevention of SSI is questionable.

Risk Factors for Sternal Wound Infection After Open Heart Operations Vary According to Type of Operation

BACKGROUND

This study evaluated whether risk factors for sternal wound infections vary with the type of surgical procedure in cardiac operations.

METHODS

This was a university hospital surveillance study of 3,249 consecutive patients (28% women) from 2006 to 2010 (median age, 69 years [interquartile range, 60 to 76]; median additive European System for Cardiac Operative Risk Evaluation score, 5 [interquartile range, 3 to 8]) after (1) isolated coronary artery bypass grafting (CABG), (2) isolated valve repair or replacement, or (3) combined valve procedures and CABG. All other operations were excluded. Univariate and multivariate binary logistic regression were conducted to identify independent predictors for development of sternal wound infections.

RESULTS

We detected 122 sternal wound infections (3.8%) in 3,249 patients: 74 of 1,857 patients (4.0%) after CABG, 19 of 799 (2.4%) after valve operations, and 29 of 593 (4.9%) after combined procedures. In CABG patients, bilateral internal thoracic artery harvest, procedural duration exceeding 300 minutes, diabetes, obesity, chronic obstructive pulmonary disease, and female sex (model 1) were independent predictors for sternal wound infection. A second model (model 2), using the European System for Cardiac Operative Risk Evaluation, revealed bilateral internal thoracic artery harvest, diabetes, obesity, and the second and third quartiles of the European System for Cardiac Operative Risk Evaluation were independent predictors. In valve patients, model 1 showed only revision for bleeding as an independent predictor for sternal infection, and model 2 yielded both revision for bleeding and diabetes. For combined valve and CABG operations, both regression models demonstrated revision for bleeding and duration of operation exceeding 300 minutes were independent predictors for sternal infection.

CONCLUSIONS

Risk factors for sternal wound infections after cardiac operations vary with the type of surgical procedure. In patients undergoing valve operations or combined operations, procedure-related risk factors (revision for bleeding, duration of operation) independently predict infection. In patients undergoing CABG, not only procedure-related risk factors but also bilateral internal thoracic artery harvest and patient characteristics (diabetes, chronic obstructive pulmonary disease, obesity, female sex) are predictive of sternal wound infection. Preventive interventions may be justified according to the type of operation.

An economic evaluation of two interventions for the prevention of post-surgical infections in cardiac surgery

OBJECTIVE

To conduct a cost-effectiveness analysis that compares two prophylactic protocols for treating post-surgical infections in cardiac surgery.

METHODS

A cost effectiveness analysis was done by using a decision tree to compare two protocols for prophylaxis of post-surgical infections (Protocol A: Those patient with positive test to methicillin-resistant Staphylococcus aureus (MRSA) colonization received muripocin (twice a day during a two-week period), with no follow-up verification. Those who tested negative did not receive the prophylaxis treatment; Protocol B: all patients received the mupirocin treatment). The number of post-surgical infections averted was the measure of effectiveness from the health system's perspective, 30 days following the surgery. The incidence of infections and complications was obtained from two cohorts of patients who underwent cardiac surgery Hospital. The times for applying the two protocols were validated by experts. They cost were calculated from the hospital's analytical accounting management system and Pharmaceutical Service. Only direct costs were taken into account, no discount rates were applied. Incremental cost-effectiveness ratio (ICER) was calculated. A probabilistic sensitivity analysis was performed.

RESULTS

A total of 1118 patients were included (721 in Protocol A and 397 in Protocol B). No statistically significant differences were found in age, sex, diabetes, exitus or length of hospital stay between the two protocols. In the control group the rate of infection was 15.3%, compared with 11.3% in the intervention group. Protocol B proves to be more effective and at a lower cost, yielding an ICER of €32,506.

CONCLUSION

Universal mupirocin prophylaxis against surgical site infections (SSI) in cardiac surgery as a dominant strategy, because it shows a lower incidence of infections and cost savings, versus the strategy to treat selectively patients according to their test results prior screening.

Deep sternal wound infection after cardiac surgery: Evidences and controversies

Despite many advances in prevention and perioperative care, deep sternal wound infection (DSWI) remains a pressing concern in cardiac surgery, with a still relevant incidence and with a considerable impact on in-hospital mortality and also on mid- and long-term survival. The permanent high impact of this complication is partially related to the increasing proportion of patients at high-risk for infection, as well as to the many patient and surgical risk factors involved in the pathogenesis of DSWI. The prophylactic antibiotic therapy is one of the most important tools in the prevention of DSWI. However, the choice of antibiotic, the dose, the duration, the adequate levels in serum and tissue, and the timing of antimicrobial prophylaxis are still controversial. The treatment of DSWI ranges from surgical revision with primary closure to surgical revision with open dressings or closed irrigation, from reconstruction with soft tissue flaps to negative pressure wound therapy (NPWT). However, to date, there have been no accepted recommendations regarding the best management of DSWI. Emerging evidence in the literature has validated the efficacy and safety of NPWT either as a single-line therapy, or as a “bridge” prior to final surgical closure. In conclusion, the careful control of patient and surgical risk factors - when possible, the proper antimicrobial prophylaxis, and the choice of validated techniques of treatment could contribute to keep DSWIs at a minimal rate.

Antibiotic prophylaxis and risk of Clostridium difficile infection after coronary artery bypass graft surgery

OBJECTIVE

Antibiotic use, particularly type and duration, is a crucial modifiable risk factor for Clostridium difficile. Cardiac surgery is of particular interest because prophylactic antibiotics are recommended for 48 hours or less (vs ≤24 hours for noncardiac surgery), with increasing vancomycin use. We aimed to study associations between antibiotic prophylaxis (duration/vancomycin use) and C difficile among patients undergoing coronary artery bypass grafting.

METHODS

We extracted data on coronary artery bypass grafting procedures from the national Premier Perspective claims database (2006-2013, n = 154,200, 233 hospitals). Multilevel multivariable logistic regressions measured associations between (1) duration (<2 days, "standard" vs ≥2 days, "extended") and (2) type of antibiotic used ("cephalosporin," "cephalosporin + vancomycin," "vancomycin") and C difficile as outcome.

RESULTS

Overall C difficile prevalence was 0.21% (n = 329). Most patients (59.7%) received a cephalosporin only; in 33.1% vancomycin was added, whereas 7.2% received vancomycin only. Extended prophylaxis was used in 20.9%. In adjusted analyses, extended prophylaxis (vs standard) was associated with significantly increased C difficile risk (odds ratio, 1.43; confidence interval, 1.07-1.92), whereas no significant associations existed for vancomycin use as adjuvant or primary prophylactic compared with the use of cephalosporins (odds ratio, 1.21; confidence interval, 0.92-1.60, and odds ratio, 1.39; confidence interval, 0.94-2.05, respectively). Substantial inter-hospital variation exists in the percentage of extended antibiotic prophylaxis (interquartile range, 2.5-35.7), use of adjuvant vancomycin (interquartile range, 4.2-61.1), and vancomycin alone (interquartile range, 2.3-10.4).

CONCLUSIONS

Although extended use of antibiotic prophylaxis was associated with increased C difficile risk after coronary artery bypass grafting, vancomycin use was not. The observed hospital variation in antibiotic prophylaxis practices suggests great potential for efforts aimed at standardizing practices that subsequently could reduce C difficile risk.

A Prolonged Post-Operative Antibiotic Regimen Reduced the Rate of Prosthetic Joint Infection after Aseptic Revision Knee Arthroplasty

BACKGROUND

The aim of this study was to compare the prosthetic joint infection (PJI) rate after knee revision arthroplasty in two consecutive periods with different antibiotic prophylaxis: short (one day) versus long (five days).

METHODS

From January 2007 to September 2010 antibiotic prophylaxis consisted of 800 mg of teicoplanin and 2 g of ceftazidime intravenously and 1 g of ceftazidime two hours after the first dose. From October 2010, it was prolonged post-operatively using vancomycin and ceftazidime intravenously until the fifth day.

RESULTS

During the study period, 341 revision surgeries met the inclusion criteria. The PJI rate was lower in the long-prophylaxis group (2.2% versus 6.9%, p=0.049). Prolonged post-operative antibiotic treatment was the only variable associated independently with a lower rate of PJI (odds ratio [OR]: 0.27, 95% confidence interval [CI]: 0.07-0.99).

Different duration strategies of perioperative antibiotic prophylaxis in adult patients undergoing cardiac surgery: an observational study

Background

All international guidelines recommend perioperative antibiotic prophylaxis (PAB) should be routinely administered to patients undergoing cardiac surgery. However, the duration of PAB is heterogeneous and controversial.

Methods

Between 01.01.2011 and 31.12.2011, 1096 consecutive cardiac surgery patients were assigned to one of two groups receiving PAB with a second-generation cephalosporin for either 56 h (group I) or 32 h (group II). Patients’ characteristics, intraoperative data, and the in-hospital follow-up were analysed. Primary endpoint was the incidence of surgical site infection (deep and superficial sternal wound-, and vein harvesting site infection; DSWI/SSWI/VHSI). Secondary endpoints were the incidence of respiratory-, and urinary tract infection, as well as the mortality rate.

Results

615/1096 patients (56,1%) were enrolled (group I: n = 283 versus group II: n = 332). There were no significant differences with regard to patient characteristics, comorbidities, and procedure-related variables. No statistically significant differences were demonstrated concerning primary and secondary endpoints. The incidence of DSWI/SSWI/VHSI were 4/283 (1,4%), 5/283 (1,7%), and 1/283 (0,3%) in group I versus 6/332 (1,8%), 9/332 (2,7%), and 3/332 (0,9%) in group II (p = 0,76/0,59/0,63). In univariate analyses female gender, age, peripheral arterial obstructive disease, operating-time, ICU-duration, transfusion, and respiratory insufficiency were determinants for nosocomial infections (all ≤ 0,05). Subgroup analyses of these high-risk patients did not show any differences between the two regimes (all ≥ 0,05).

Conclusions

Reducing the duration of PAB from 56 h to 32 h in adult cardiac surgery patients was not associated with an increase of nosocomial infection rate, but contributes to reduce antibiotic resistance and health care costs.

Management practices and major infections after cardiac surgery

BACKGROUND

Infections are the most common noncardiac complication after cardiac surgery, but their incidence across a broad range of operations, as well as the management factors that shape infection risk, remain unknown.

OBJECTIVES

This study sought to prospectively examine the frequency of post-operative infections and associated mortality, and modifiable management practices predictive of infections within 65 days from cardiac surgery.

METHODS

This study enrolled 5,158 patients and analyzed independently adjudicated infections using a competing risk model (with death as the competing event).

RESULTS

Nearly 5% of patients experienced major infections. Baseline characteristics associated with increased infection risk included chronic lung disease (hazard ratio [HR]: 1.66; 95% confidence interval [CI]: 1.21 to 2.26), heart failure (HR: 1.47; 95% CI: 1.11 to 1.95), and longer surgery (HR: 1.31; 95% CI: 1.21 to 1.41). Practices associated with reduced infection risk included prophylaxis with second-generation cephalosporins (HR: 0.70; 95% CI: 0.52 to 0.94), whereas post-operative antibiotic duration >48 h (HR: 1.92; 95% CI: 1.28 to 2.88), stress hyperglycemia (HR: 1.32; 95% CI: 1.01 to 1.73); intubation time of 24 to 48 h (HR: 1.49; 95% CI: 1.04 to 2.14); and ventilation >48 h (HR: 2.45; 95% CI: 1.66 to 3.63) were associated with increased risk. HRs for infection were similar with either <24 h or <48 h of antibiotic prophylaxis. There was a significant but differential effect of transfusion by surgery type (excluding left ventricular assist device procedures/transplant) (HR: 1.13; 95% CI: 1.07 to 1.20). Major infections substantially increased mortality (HR: 10.02; 95% CI: 6.12 to 16.39).

CONCLUSIONS

Major infections dramatically affect survival and readmissions. Second-generation cephalosporins were strongly associated with reduced major infection risk, but optimal duration of antibiotic prophylaxis requires further study. Given practice variations, considerable opportunities exist for improving outcomes and preventing readmissions. (Management Practices and Risk of Infection Following Cardiac Surgery; NCT01089712).

Cardiac surgery antibiotic prophylaxis and calculated empiric antibiotic therapy

BACKGROUND

Ongoing debate exists concerning the optimal choice and duration of antibiotic prophylaxis as well as the reasonable calculated empiric antibiotic therapy for hospital-acquired infections in critically ill cardiac surgery patients.

METHODS

A nationwide questionnaire was distributed to all German heart surgery centers concerning antibiotic prophylaxis and the calculated empiric antibiotic therapy.

RESULTS

The response to the questionnaire was 87.3%. All clinics that responded use antibiotic prophylaxis, 79% perform it not longer than 24 h (single-shot: 23%; 2 doses: 29%; 3 doses: 27%; 4 doses: 13%; and >5 doses: 8%). Cephalosporin was used in 89% of clinics (46% second-generation, 43% first-generation cephalosporin). If sepsis is suspected, the following diagnostics are performed routinely: wound inspection 100%; white blood cell count 100%; radiography 99%; C-reactive protein 97%; microbiological testing of urine 91%, blood 81%, and bronchial secretion 81%; procalcitonin 74%; and echocardiography 75%. The calculated empiric antibiotic therapy (depending on the suspected focus) consists of a multidrug combination with broad-spectrum agents.

CONCLUSION

This survey shows that existing national guidelines and recommendations concerning perioperative antibiotic prophylaxis and calculated empiric antibiotic therapy are well applied in almost all German heart centers.

Role of topical application of gentamicin containing collagen implants in cardiac surgery

Sternal wound infections (SWI) continue to be a major cause of concern after cardiac surgery. It leads to prolonged hospital stay and increased morbidity, mortality and increased hospital costs. Prophylactic systemic antibiotics have been used to prevent surgical site infection (SSI). However, prolonged postoperative use of systemic antibiotics can lead to emergence of resistant organisms. Gentamycin Containing Collagen Implants (GCCI) when used during sternotomy closure produces high local antibiotic concentrations in the wound with a low serum concentration. There is evidence that the concentration of gentamicin in the mediastinal fluid reaches levels high enough to be effective against bacteria that are considered resistant to gentamycin and other antibiotics.However, questions have been raised about the safety and efficacy of GCCI. There were concerns whether GCCI can lead to systemic absorption with renal impairment and whether use of topical antibiotics can lead to emergence of antimicrobial resistance.We, hereby, review the literature on GCCI (Collatamp) and take the opportunity to appraise the scientific community about their role in cardiac surgery. Several recent studies have supported their clinical effectiveness. They should be used in dry condition and should not be soaked in saline even for a short period prior to use. However, for GCCI to become part of routine practice in cardiac surgery further large randomised studies are required. As the incidence of sternal wound infection is low in the specialty of cardiac surgery, for any study to be sufficiently powered to address this issue, multicenter studies might be the way forward.Based on the evidence presented in this manuscript it is recommended GCCI (Collatamp) can be a cost effective adjunct for prevention of sternal wound infection. They can also be used for treatment of Deep Sternal Wound Infection.

Sternal wound infection caused by Mycobacterium chelonae

INTRODUCTION

Sternal wound infection caused by Mycobacterium chelonae, a member of the rapidly growing nontuberculous mycobacteria (NTM), is rare and may present without signs and symptoms of systemic infection.

METHODS

We present a patient who had a M. chelonae infection of the sternum following excision of a left atrial myxoma and conducted a review of the literature from 1976 to 2013.

RESULTS

Seventy cases of NTM sternal wound infection after cardiac surgery were identified, including six outbreaks and ten sporadic cases including the present case. Thirty-four cases were isolated coronary artery bypass grafting (CABG) surgery, 16 cases were isolated valve replacement, and two cases were valve replacement with CABG. The age range of the patients was between 6 and 78 years. The average time from the surgery was 49 ± 58 days which was longer than the usual bacterial mediastinitis. The overall mortality rate was 29%.

CONCLUSION

NTM sternal wound infection is rare but may be fatal if not properly treated. The toxic signs are often subtle and it will take longer to isolate compared to typical bacterial mediastinitis. Early recognition, the use of appropriate antibiotics based on susceptibility tests, and aggressive surgical debridement are required for full recovery.

Effectiveness of a bundled intervention of decolonization and prophylaxis to decrease Gram positive surgical site infections after cardiac or orthopedic surgery: systematic review and meta-analysis

OBJECTIVE

To evaluate studies assessing the effectiveness of a bundle of nasal decolonization and glycopeptide prophylaxis for preventing surgical site infections caused by Gram positive bacteria among patients undergoing cardiac operations or total joint replacement procedures.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

PubMed (1995 to 2011), the Cochrane database of systematic reviews, CINAHL, Embase, and clinicaltrials.gov were searched to identify relevant studies. Pertinent journals and conference abstracts were hand searched. Study authors were contacted if more data were needed.

ELIGIBILITY CRITERIA

Randomized controlled trials, quasi-experimental studies, and cohort studies that assessed nasal decolonization or glycopeptide prophylaxis, or both, for preventing Gram positive surgical site infections compared with standard care.

PARTICIPANTS

Patients undergoing cardiac operations or total joint replacement procedures. DATA EXTRACTION AND STUDY APPRAISAL: Two authors independently extracted data from each paper and a random effects model was used to obtain summary estimates. Risk of bias was assessed using the Downs and Black or the Cochrane scales. Heterogeneity was assessed using the Cochran Q and I(2) statistics.

RESULTS

39 studies were included. Pooled effects of 17 studies showed that nasal decolonization had a significantly protective effect against surgical site infections associated with Staphylococcus aureus (pooled relative risk 0.39, 95% confidence interval 0.31 to 0.50) when all patients underwent decolonization (0.40, 0.29 to 0.55) and when only S aureus carriers underwent decolonization (0.36, 0.22 to 0.57). Pooled effects of 15 prophylaxis studies showed that glycopeptide prophylaxis was significantly protective against surgical site infections related to methicillin (meticillin) resistant S aureus (MRSA) compared with prophylaxis using β lactam antibiotics (0.40, 0.20 to 0.80), and a non-significant risk factor for methicillin susceptible S aureus infections (1.47, 0.91 to 2.38). Seven studies assessed a bundle including decolonization and glycopeptide prophylaxis for only patients colonized with MRSA and found a significantly protective effect against surgical site infections with Gram positive bacteria (0.41, 0.30 to 0.56).

CONCLUSIONS

Surgical programs that implement a bundled intervention including both nasal decolonization and glycopeptide prophylaxis for MRSA carriers may decrease rates of surgical site infections caused by S aureus or other Gram positive bacteria.

Effect of inspiratory muscle training before cardiac surgery in routine care

BACKGROUND

Inspiratory muscle training (IMT) before cardiac surgery has proved to be a promising intervention to reduce postoperative pneumonia in a randomized controlled trial setting. Effects of IMT in routine care have not been reported.

OBJECTIVE

The purpose of this study was to investigate the effect of IMT before cardiac surgery on postoperative pneumonia in routine care at a Dutch university medical center using propensity scoring.

DESIGN

This was an observational cohort study.

METHODS

All candidates for cardiac surgery were preoperatively stratified by a physical therapist for low risk or high risk for postoperative pulmonary complications. Patients at high risk either engaged in an unsupervised IMT program (20 minutes a day) at home for at least 2 weeks before surgery (group 1) or received usual care (no IMT) (group 2). Results in terms of outcome measures were adjusted with propensity scores to reduce bias caused by nonrandom treatment assignment.

RESULTS

The results showed that of the 94 patients at high risk in group 1, 1 patient (1.1%) developed a postoperative pneumonia. In group 2, 8 out of the 252 patients at high risk (3.2%) developed this pulmonary complication (adjusted odds ratio=0.34, 95% confidence interval=0.04-3.38). No significant differences were found regarding median (25th-75th percentile) ventilation time (7 [5-9] hours versus 7 [5-10] hours), length of stay in the intensive care unit (23 [21-24] hours versus 23 [21-25] hours), or total postoperative length of stay (7 [6-11] days versus 7 [5-9] days).

LIMITATIONS

The most important limitations of this study were confounding, incomplete data collection, and a low incidence of the primary outcome.

CONCLUSIONS

Propensity scoring is believed to be a valuable tool of great potential interest to researchers in the field of observational studies. Whether IMT in routine care resulted in less postoperative pneumonia cannot be concluded.

Antibiotic prophylaxis for cardiac surgery

Antibiotic prophylaxis for cardiac surgery is a controversial area. Recent systematic reviews and meta-analyses of randomized controlled trials have concluded that surgical site infection can be reduced by prolonging prophylaxis for 24-48 h. Also, post-operative pneumonia and all-cause mortality can be reduced by giving agents with both anti-Gram-negative and anti-Gram-positive activity. The choice of the most appropriate regimen remains open to debate.