Filter Life In Renal Replacement Therapy

Dialysis is the process of removing fluid and waste products from the blood of patients who have kidney failure. Most people may be familiar with conventional hemodialysis in specialized kidney wards, for patients who have kidney disease and are otherwise well. It is usually performed for around 4 hours, 3 days per week, however these short periods of high intensity dialysis are often not tolerated by the very sick who are better managed with less intense but continuous dialysis. This continuous type of dialysis is called Continuous Renal Replacement Therapy (CRRT) and it is continued in patients in ICU who have kidney failure, until the patient’s kidneys start to work again or they are well enough to move to intermittent dialysis in a kidney ward. During dialysis, blood from the patient is continuously circulated through a filter in the kidney machine, and waste products are removed. There is always the possibility that the blood may clot as it passes through the filter. Patient stability and carefully controlled fluid removal can be compromised if the kidney machine fails too frequently. The most common reason for failure is blood clotting inside the filter – the more this occurs, the less the patient actually receives treatment, and as each filter costs roughly $400 the treatment becomes increasingly expensive. If blood clotting is prevented inside the filter it can last longer - between 24 and 72 hours. Common methods to stop blood clotting (known as anti-coagulation) include adding heparin or citrate to the circuit in the dialysis machine. The primary aim of this study is to compare the filter life using two methods of anticoagulation in CRRT in the Alfred Intensive Care Unit. The first method involves the use of a blood thinner called heparin. Sometimes when higher doses of heparin are required, another drug called protamine that reverses the blood thinning effect is added to the blood in kidney machine circuit. Adding heparin with or without protamine is the method that is currently most used at the Alfred for CRRT. The second method involves the use of citrate fluid in the kidney machine. The citrate binds with calcium and has an anticoagulant effect. Previously, this method proved more labor intensive for the nurses as additional pumps were needed. It tended to be used in special situations e.g. in patients who were allergic to heparin and/or could not receive blood thinners due to a high risk of bleeding. However, recent improvements in the technology of kidney machines have allowed this method to be used much more simply and efficiently. This study has been designed by our doctors at the Alfred Intensive Care Unit to find out if using citrate in the kidney machine is a better and safer way of using CRRT than using heparin in the kidney machine.