Antibiotics are routinely used to prevent surgical wound infection. Vancomycin is a widely used antibiotic for surgery in patients with an allergy to penicillin. During cardiac surgery, cardiopulmonary bypass (CPB) and modified ultrafiltration (MUF) are routinely used and can lower the level of the antibiotic. The purpose of this study is to quantify the change in plasma vancomycin concentration associated with cardiopulmonary bypass and modified ultrafiltration.

Subjects having cardiac surgery in which they will be on a heart-lung machine and will receive the antibiotic vancomycin, will be able to participate.

Up to ten blood samples testing for vancomycin concentrations will be collected in subjects administered vancomycin as prophylaxis before cardiac surgery with cardiopulmonary bypass and modified ultrafiltration. Participation will be complete once the cardiac surgery has been finished.

Inclusion Criteria:

• Scheduled to undergo cardiac surgery with cardiopulmonary bypass and modified ultrafiltration
• age greater than 18 years old
• penicillin allergy or in-hospital stay greater than 24 hours
• normal renal function
• normal liver function
• absence of clinical and laboratory signs of infection

Exclusion Criteria:

• vancomycin allergy
• pregnancy
• impaired renal function
• impaired liver function
• morbid obesity
• active infections
• Jehovah's Witness

12 hours