Dosing of antibiotics in critically ill patients undergoing renal replacement therapy

On September 11, 1945 Maria Schafstaat was the first patient who successfully underwent a dialysis treatment for acute kidney injury (AKI), formerly known as acute renal failure. Since then, the number of patients with AKI is increasing worldwide. Today AKI is generally one feature of a multiple organ dysfunction syndrome (MODS), which develops in response to major surgery, cardiogenic shock or sepsis. Several clinical studies have shown that early and appropriate antibiotic therapy in those patients is of utter importance, yet it remains one of the most difficult challenges to meet. Even in critically ill patients with conserved renal function a myriad of pathophysiological changes, resulting in increased volume of distribution, decreased protein binding and altered hepatic drug clearance, makes appropriate antibiotic dosin difficult. Adequate pharmacotherapy, i.e. dose of anti-infective agens is becoming even more complicated if it has to be tailored to counteract their removal by different modes and intensities of renal replacement therapy. This review summarizes our sparse knowledge about pharmacokinetic studies and dosing recommendations of drugs in patients with AKI undergoing continuous renal replacement therapies (CRRTs) such as continuous venovenous hemofiltration (CVVH) as well as extended dialysis (ED), an increasingly used method to treat patients with AKI in the intensive care setting. We reflect on failure of several large prospective controlled studies to show a survival benefit of higher doses of renal replacement therapy, a finding that might be caused by the fact that we still adhere to dosing guidelines for antibiotics which are at best ineffectual but might also lead to potentially dangerous underdosing of these life saving drugs. Lastly we address possible strategies to overcome the lack of knowledge, the lack of data and the lack of interest in this important area of critical care medicine. Improvement of clinical outcomes and reduction of antibiotic resistance in this patient population will require nephrologist, intensivists and pharmacists to work together.