Medication dosing in critically ill patients with acute kidney injury treated with renal replacement therapy

Critically ill patients with acute kidney injury may be treated with a variety of renal replacement therapies (RRTs). Each of these RRTs has profound yet differing effects on drug dosing. Although the doses of some drugs can be titrated to an immediately observable pharmacodynamic effect, the effects of many drugs, such as antibiotics for example, are not immediately apparent. Attainment of desired pharmacodynamic response is a complex interplay between patient, RRT, and pharmacokinetic factors. In the case of antibiotics, microorganism-specific factors also must be considered. Rational and effective drug dosing in this clinical setting cannot occur until all these issues are addressed by the clinician. Failure to account for the pharmacokinetic influences of critical illness, kidney disease, and choice of intermittent hemodialysis or prolonged intermittent or continuous RRT can contribute to the high mortality rates seen in these patients. Pharmacotherapy considerations for each of these therapies are addressed in this article by applying them to a patient case.