A haemofilter is a machine used to perform continuous renal replacement therapy (CRRT), a form of kidney support for critically ill patients whose kidneys are unable to adequately filter the blood and remove waste products and excess fluid. Unlike conventional haemodialysis (which runs intermittently over 3 to 4 hours), CRRT using a haemofilter runs continuously over 24 hours, making it suitable for intensive care patients who are too unstable to tolerate the fluid shifts of intermittent dialysis.
The haemofilter works by drawing blood from a large vein (via a central venous catheter) through a specialised membrane filter. The filter removes excess fluid, metabolic waste products such as urea and creatinine, and electrolytes. The cleaned blood is returned to the patient. Replacement fluid may be added to maintain the patient’s volume and electrolyte balance, depending on the specific technique used.
In the intensive care unit following cardiac arrest, acute kidney injury (AKI) is a recognised complication of post-cardiac arrest syndrome. Hypoperfusion of the kidneys during the arrest, the systemic inflammatory response of resuscitation, and the effects of contrast dye from coronary angiography can all contribute to AKI. When kidney function deteriorates sufficiently or fluid overload cannot be managed with diuretics, a haemofilter is commenced.
Most patients who require haemofilter support after cardiac arrest can recover kidney function once their overall condition stabilises. Complete recovery is possible, though long-term dialysis may be needed in patients with pre-existing kidney disease or extensive injury. The clinical team will explain to families why the haemofilter has been started and what the goals of treatment are.
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