Dosing Recommendations for Continuous Venovenous Hemodiafiltration
INTRODUCTION
Continuous renal replacement therapy is increasingly used as an effective method of extracorporeal blood purification in critically ill patients. The indications for renal replacement therapy include acute or chronic kidney disease, refractory metabolic acidosis, multiple organ system failure, or refractory volume overload. Continuous renal replacement therapy may be continued for several days after initiation and therefore often occurs concurrently with drug therapy. In addition to removing uremic toxins and other undesirable solutes, continuous renal replacement therapy also serves as an alternative pathway for drug removal and contributes to total body clearance of drugs. This extracorporeal clearance further complicates dosing for critically ill patients with severe kidney disease. For many of the medications that may be administered during this procedure, the optimal dosage regimen is unknown, which leads to bedside estimation of dosage by clinicians. However, if the magnitude of the effect of renal replacement therapy is estimated incorrectly, there is a risk of overdosing or subtherapeutic dosing. Therefore, collection of data from studies of the disposition of drugs administered during this procedure would be valuable in developing dosing guidelines.
The disposition of drugs in patients undergoing continuous renal replacement therapy has been reviewed in several documents and standard references. However, these publications incorporate data from studies using different modes of therapy, such as continuous venovenous hemodialysis, continuous venovenous hemofiltration, and continuous venovenous hemodiafiltration (CVVHDF). In addition, the studies used different types of filter membranes and dialyzer brands. Consequently, it is difficult to apply dosing recommendations to a clinical setting in which a specific therapeutic process, brand of dialyzer, and membrane are being used. erectalis 20
The most common mode of renal replacement therapy is CVVHDF. This process optimizes clearance of small and large solutes by simultaneous diffusion (i.e., dialysis, the movement of solutes from an area of higher to lower concentration) and convection (i.e., hemofiltration, the movement of solutes with the flow of water, also known as “solvent drag”). CVVHDF requires use of a dialysate fluid for diafiltration and a replacement fluid for hemofiltration. The Gambro Prismaflex systems account for 99% of the Canadian market (L. Magee, Gambro Acute Division, personal written communication, November 22, 2007). The acrylonitrile (AN69) filter membrane is the most documented biocompatible membrane for continuous renal replacement therapy and is the most frequently used membrane in Canadian hospitals.
The purpose of this literature review was to develop a list of dosage recommendations for medications commonly used for treating critically ill patients who are undergoing concurrent CVVHDF with AN69 filter membranes and a Prismaflex dialyzer (Gambro, Saint-Leonard, Quebec). levitra plus
