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Resource type: Article

Kidney machine or "filter"

What is a kidney machine or filter?

A kidney machine or filter is a form of kidney or renal support.It is also known as Continuous Veno Venous Haemofiltration (CVVH). We prefer to use this form of support in Intensive Care as it is gentler on the heart and circulation than other forms of kidney or renal support eg dialysis.

What is a kidney machine or filter used for?

The filter or kidney machine is a machine that can temporarily take over the work of the kidneys when they are struggling to work normally. We can monitor how well the patient's kidneys are working by recording the amount of urine they pass and by doing simple blood tests.The kidneys can struggle for a great many reasons,but "acute" (recent onset) kidney or renal failure is potentially reversible, depending on the cause and how quickly it is treated.

How does a kidney machine filter work?

In order to attach a patient to this machine, we insert a line into a large vein, usually in the neck or groin.The CVVH machine (or “filter”) is designed to temporarily take over the work of the kidneys.The patient’s blood is passed through a set of tubing and a special membrane (or filter) which removes harmful waste products which might otherwise build up. Replacement fluid containing important electrolytes (blood salts and minerals) is added and the “filtered” blood is returned to the patient.Patients usually also receive intravenous blood thinning drugs (into the bloodstream) to prevent blood clots while receiving this treatment. The nurse will carefully check that the patient is receiving just the right amount of blood thinner (not too much and not too little) whilst he or she is attached to the filter or kidney machine.

How long is the kidney machine or filter used for?

This gentle procedure can be carried out continuously over many hours and may be carried out daily and over a number of days until the patient’s kidneys start to recover. Passing urine is a sign of recovery. Routine blood tests will also tell us when the patient’s kidneys have recovered well enough for us to remove the machine.

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