In reply: Professor Shann raises three issues regarding the recommendation for 24 hours’ prophylaxis for cardiac surgery. First, he states that the trial1 on which this recommendation was made was flawed, because “cephazolin was not given until 20–30 minutes after induction of anaesthesia, which is likely to have been too late”. The trial included patients having coronary artery surgery and/or cardiac valve replacement, and, for these procedures, the time between induction of anaesthesia and surgical incision is about 60–75 minutes, as patients require the placement of intravenous lines and preparation for coronary artery bypass surgery. Antibiotic administration is recommended 30–60 minutes before incision, thus, administration 30 minutes after induction provides optimal serum concentrations at incision, in patients undergoing cardiac surgery. Second, the per-protocol analysis is perhaps less than ideal, but the demographics, clinical characteristics and operative data were comparable for the patients included in the analysis. Third, as stated by Professor Shann, the three earlier studies2-4 were either very small or flawed in design. The McDonald systematic review5 included 28 studies, only two of which were on cardiac surgery, both being the earlier flawed studies2,3 quoted above.
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