CLINICAL PHARMACOKINETICS DURING CONTINUOUS HEMOFILTRATION

Continuous haemofiltration is an extracorporeal technique that is incr easingly used to remove fluid, electrolytes, and other waste products from the blood supply of critically ill patients with acute renal fail ure. Continuous arteriovenous haemofiltration (CAVH), where the blood exits the body from an artery and re-enters through a vein, is widely used. Continuous venovenous haemofiltration (CVVH), where blood both e xits and enters through a vein by way of a mechanical pump, avoids pro blems that result from the variable ultrafiltration rate found during CAVH. Continuous arteriovenous or venovenous haemodiafiltration (CAVHD or CVVHD) combine continuous haemofiltration and haemodialysis. All m ethods involve ultrafiltration of the patient's blood through a filter that is highly permeable to water and small molecules. Drug eliminati on by haemofiltration depends mainly on the rate of ultrafiltration, t he drug protein binding and the sieving coefficient of the membrane. B ecause patients undergoing continuous haemofiltration have impaired re nal function, dosage reduction is often recommended so that adverse dr ug reactions are avoided. In contrast, if drug removal by haemofiltrat ion is significant, dosage supplementation may be required to ensure t herapeutic efficacy of the drug. Therefore, knowledge of the impact of continuous haemofiltration on drug elimination and the pharmacokineti c profile of drugs is essential to good clinical management. The curre ntly available information on the clinical pharmacokinetic aspects of drug therapy during continuous haemofiltration are summarised. Drugs c ommonly associated with haemofiltration therapy are tabulated with upd ated pharmacokinetics and drug-monitoring information.