Abstract

Objective Prospective studies show 10% incidence of Sternal Wound Infection (SWI) for 90 day follow-up, compared to infection rates of 5% reported by the National Nosocomial Infection Surveillance (NNIS) with only 30-days follow-up. This incidence increases 2-3 times in high risk patients. We hypothesised that longer duration (48 hours) and broader spectrum antibiotic prophylaxis would be more effective in high risk patients.

Design Prospective randomised controlled clinical trial.

Setting Cardiothoracic centre, United Kingdom.

Patients and Methods Patients were eligible if they were undergoing median sternotomy for primary isolated coronary artery bypass grafting (CABG), with at least one internal thoracic artery (ITA) used for coronary grafting and having one or more of the following 3 risk factors: (1) Obesity defined as Body Mass Index (BMI) > 30kg/m2, (2) Diabetes Mellitus (DM) or (3) bilateral internal thoracic arteries (BITA) grafts( ie the use of the other ITA).

Interventions The study group received a single dose of Gentamicin 2mg/kg, Rifampicin 600mg, and Vancomycin 15mg/kg with 3 further doses of 7.5mg/kg 12 hourly. Control group received Cefuroxime 1.5gm at induction and 3 further doses of 750mg at 8 hourly intervals.

Main outcome measures Primary end point was the incidence of SWI at 90 days. Secondary end point was the antibiotic and hospital costs.

Results During the study period, 486 patients underwent isolated CABG with a 30-days SWI of 7.6%. 186 high-risk patients were recruited and analysed; 87 in the study group and 99 in the control group. 90-day SWI was significantly reduced in the study group; 8 patients (9.2%; 95% CI: 3.5%, 15.3%) compared to the control group 25 patients (25.2%; 95% CI: 19.5%, 39.4%) (p=0.004). The study group had significantly lower cost of antibiotics (21.2% reduction - US$96/patient) (p<0.001), and significantly lower hospital cost (20.4% reduction in cost - US$3800/patient) (p=0.04).

Conclusions This prospective randomised controlled clinical trial shows that longer and broader- spectrum antibiotic prophylaxis significantly reduces the incidence of SWI in high risk patients, with significant economic benefit in terms of costs of antibiotics as well as hospital costs.