Perioperative antibiotic prophylaxis in adults - Sistema Nazionale ...

either they were not specifically designed with this issue in mind or, if they were,they were methodologically unreliable.In a recent cohort study of patients undergoing cardiac surgery, an analysis of subgroupsshowed that the risk of SSI was reduced by an intraoperative dose ofantibiotic only when the operation lasted more than 400 minutes from the firstadministration 175 .A systematic review of the literature referring to patients receiving prophylaxis forcolorectal surgery found no evidence that drugs with a long half-life were moreeffective than those with a short half-life 31 ; this is further evidence of the limitedusefulness of maintaining high serum levels of antibiotic for a long time.In conclusion, no clear evidence has yet emerged for or against the administration ofadditional doses of antibiotic during surgery. However, most guidelines 1,22,23,25,26 ,endorse the 1984 recommendation of Stone 176 to administer a second, intraoperativedose if the operation is still in progress when the period since it began is equivalent todouble the half-life of the antibiotic used.RecommendationAlbeit in the absence of definitive data, most guidelines suggest administering anintraoperative dose of antibiotic when the duration of the operation is equal to doublethe half-life of the drug used.Serum antibiotic levels are reduced by blood loss and fluid replacement, particularlyif these occur during the first hour of surgery, when plasma drug levels are high 177,178 .The precise effects of blood loss and fluid replacement are difficult to predict andwill depend on the particular antibiotic used, the timing and extent of blood loss andfluid replacement 136 .In any case, the effect of intraoperative bleeding and fluid replacement on serum druglevels in adults is generally negligible 179,180 .