A haemofiltration machine will be used if a patient cannot remove toxins or fluid from the body independently. This is usually the function of the kidneys. In critical illness there is often a time when the kidneys function less efficiently or not at all and it is important that we use the haemofiltration to support the patient. This is a complex procedure and will always be done with full explanation and for the minimum time. It involves taking blood from the patient and passing it through a filtration system, using specialised fluid to clear the toxins and returning the blood back to the patient.