RecruitingPhase 4Drug trialDuration of Cardiac Antimicrobial Prophylaxis Outcomes StudyThis multicentre, adaptive, pragmatic, double-blind, three-arm, placebo-controlled, randomised, non-inferiority clinical trial will compare the incidence of surgical site infection and other healthcare associated infections, health economic and microbiological impact after intraoperative only (Arm A), to 24 hours (Arm B) and, to 48 hours (Arm C) of IV cefazolin and placebo postoperative surgical antimicrobial prophylaxis in patients undergoing cardiac surgery