Prescription of antimicrobial agents in patients undergoing continuous renal replacement therapy

The prescription of antibiotics to critically ill patients is an extremely common intervention. Early and appropriate antimicrobial administration has been repeatedly shown to improve mortality in septic patients [1-7]. However, whilst the choice of drug class will normally be influenced by numerous factors such as the likely organism, the current unit flora, and the patient's comorbidities, the dose prescribed will usually be a standard one, perhaps modified by an estimated glomerular filtration rate (GFR) or a suggested dialysis dose. Yet, in the critically ill, a host of factors may influence the therapeutic level of prescribed antibiotics. These include increased volumes of distribution, changes in protein binding and increased extrarenal and renal losses all of which may contribute to lower than predicted drug levels when the usual patient dosage regimens are used [8]. The problem becomes more complex when renal failure supervenes. The addition of renal replacement therapy, restoration of renal function during recovery and alterations in volume of distribution may all lead to lowered tissue levels of antibiotics, with the potential to increase morbidity and mortality through inadequate antibiotic activity [9, 10]