blood drops
In ultrafiltration, a patient’s blood passes through a filter that removes the excess fluid from the blood. The filtered blood -- free of the excess fluid -- is then returned to the patient.
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Ultrafiltration is a medical therapy that removes excess salt and water from the bodies of patients who have a condition called fluid overload. In this procedure, which uses a small, portable machine, the patient's blood is passed through a filter that removes the excess fluid from the blood. The filtered blood -- free of the excess fluid -- is then returned to the patient.

With ultrafiltration, the rate of fluid removal is adjustable, so doctors can gradually remove the excess fluid without upsetting blood pressure, heart rate or electrolyte balance (chemical substances like sodium, potassium and chloride). Up to 500 milliliters, or 1.1 pound, of fluid can be safely removed per hour. The average removal rate is 250 milliliters, or about a half pound, an hour, and treatment usually lasts about 24 hours. In general, people receiving ultrafiltration therapy stay in the hospital for three to four days.


This therapy can be used in combination with or as an alternative to diuretics (drugs that help rid the body of excess water), inotropic drugs (medicines that stimulate the heart to expel more blood with each beat) or vasodilator drugs (medicines that widen blood vessels) to achieve the target fluid removal goal for the patient. And, because it removes sodium and resets body fluid levels, ultrafiltration may also improve the effectiveness of oral diuretics ("water pills") that patients take on an ongoing basis.

A clinical study called "Ultrafiltration vs Intravenous Diuretics for Patients Hospitalized for Acute Decompensated Congestive Heart Failure" (UNLOAD) compared the safety and efficacy of ultrafiltration treatment with diuretics given intravenously (that is, with a needle into the bloodstream) to treat fluid overload in heart failure patients. Results of the UNLOAD study showed that ultrafiltration not only removed more fluid than intravenous diuretics, but far fewer patients who received ultrafiltration had to return to the hospital, emergency room or clinic for worsening heart failure.

Compared to traditional dialysis equipment, the device used in ultrafiltration therapy needs only a small amount of blood (33 milliliters, or 2.5 tablespoons) from one of the patient's peripheral veins (like one in an arm). It is highly automated and can be operated by nonspecialized health care professionals in diverse locations in and outside the hospital.

In contrast, dialysis is used on patients suffering from kidney (renal) failure. Dialysis requires large amounts of blood (200-300 milliliters -- 20 tablespoons or more) and central venous access (that is, use of one of the deeper veins of the chest, neck or groin that leads directly to the heart). Plus, dialysis equipment must be operated by specialized dialysis health care professionals in intensive care settings in a hospital or clinic.


What causes fluid overload?

The main cause of fluid overload is heart failure (also called congestive heart failure), a condition in which the heart is weakened and can't circulate enough blood to the body's other organs. When the flow of blood out of the heart slows, fluid builds-up in the body's tissues and the kidneys aren't able to get rid of the excess sodium (salt) and water.

Excess fluid can build up in various locations in the body, leading to swelling in the feet, ankles and lower legs (peripheral edema) and/or swelling in the abdomen (ascites). When excess fluid collects in the lungs, the condition is called pulmonary edema.


Fluid overload can also occur as a result of some other health conditions, including kidney disease and liver disease. It can also be a side effect of some medications.

According to the National Institutes of Health, almost 5 million people in the United States have heart failure, the foremost cause of fluid overload. Each year, about 550,000 new cases of heart failure are diagnosed. While the condition can develop in people of all ages, heart failure is more common among the elderly. Medicare data shows that heart failure is the most common diagnosis among elderly people who are hospitalized. And because the American population is aging, the number of people diagnosed with heart failure is increasing every year. Heart failure is also more common among people who are overweight or obese. Excess weight puts a greater strain on the heart. It also can lead to type 2 diabetes, which adds to the risk of heart failure.

To learn more about ultrafiltration and heart failure, take a look at the links on the next page.


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  • Adams KF, Lindenfeld J, Arnold JMO, et al. Heart Failure Society of America (HFSA) 2006 Comprehensive Heart Failure Practice Guideline. J Cardiac Failure 2006;12:e1-e122.
  • Agostoni P, Marenzi G, Lauri G, et al. Sustained improvement in functional capacity after removal of body fluid with isolated ultrafiltration in chronic cardiac insufficiency: failure of furosemide to provide the same result. Am J Med. 1994;96:191-199.
  • Agostoni P, Marenzi GC, Pepi M, et al. Isolated ultrafiltration in moderate congestive heart failure. J Am Coll Cardiol. 1993;21:424-431.
  • Bart B, Boyle A, Bank AJ, et al. The RAPID Study: Ultrafiltration versus usual care for hospitalized patients with heart failure: the Relief for Acutely Fluid-Overloaded Patients With Decompensated Congestive Heart Failure. J Am Coll Cardiol. 2005;46:2043-2046.
  • Costanzo MR, Guglin ME, Saltzberg MT, et al. The UNLOAD Study: Ultrafiltration versus intravenous diuretics for patients hospitalized for acute decompensated heart failure. J Am Coll Cardiol. 2007; 49:675-683. http://www.unloadstudy.com
  • Costanzo MR, Saltzberg M, O'Sullivan J, et al. The EUPHORIA Study: Early ultrafiltration in patients with decompensated heart failure and diuretic resistance. J Am Coll Cardiol. 2005;46:2047-2051.
  • Elkayam U, Hatamizadeh P, Janmohamed M. The challenge of correcting volume overload in hospitalized patients with decompensated heart failure. J Am Coll Cardiol. 2007;49:684-686.
  • Jaski B, Ha J, Denys BG, et al. The SAFE Study: Peripherally inserted veno-venous ultrafiltration for rapid treatment of volume overloaded patients. J Card Fail. 2003;9:227-231.
  • Marenzi G, Lauri G, Grazi M, et al. Circulatory response to fluid overload removal by extracorporeal ultrafiltration in refractory congestive heart failure. J Am Coll Cardiol. 2001;38:963-968.
  • Pepi M, et al. Sustained cardiac diastolic changes elicited by ultrafiltration in patients with moderate congestive heart failure: pathophysiological correlates. Br Heart J. 1993;70:135-140.