The Food and Drug Administration warned kidney dialysis patients Friday that an adapter for certain dialysis catheters could break apart, putting them at risk of bleeding to death at home.

Only a small portion of kidney dialysis patients have this type of dialysis equipment, said Dr. Bruce Burlington, the FDA's medical device chief.But home dialysis patients should immediately check whether they have the at-risk device - something Burlington said is easy to tell - so they can get a simple but vital repair.

The FDA knows of three patients who died in their sleep and another five who suffered serious bleeding when the device, made by Pennsylvania-based Medcomp Inc., suddenly broke.

The agency notified hospitals and dialysis centers Friday to check dialysis patients for the recalled device, Medcomp's Tesio Extension Adapters, that are part of a dialysis accessory kits sold between October and February in 11 states and nine other countries.

Some kidney patients undergoing longterm dialysis have two indwelling catheters in a vein in their shoulder. One has red plastic fittings, the other blue.

The catheters attach to an extension tube that fits on the dialysis machine. An adapter where the catheter meets this little extension tube, an inch or two away from the skin, contains a clamp that seals the catheter. Without that seal, patients will bleed - because the catheter actually sits in an open vein.

The problem adapters appear to break right in front of the clamp, Burlington explained. All of the breaks occurred when patients were at home and not during dialysis itself.

How does a patient know if he or she is at risk?

Only those with two separate, single-lumen catheters are, said Burlington. Those people, he said, should examine their catheters. If they have an adapter with little wings, almost like a small wing-nut, they're not at risk, he said.

But any patient whose catheters have a knob-shaped adaptor - or who are not sure what kind they have - should immediately contact their dialysis center or hospital, the FDA said.

One of the deaths was in England. Burlington could only say that the other seven problems occurred in the United States. About 7,000 of the devices were distributed in California, Florida, Michigan, Minnesota, Missouri, New Jersey, Tennessee, Texas, Utah, Virginia and Washington.

They also were sold in Germany, Greece, Portugal, Saudi Arabia, Spain, Sweden, Switzerland, Britain and Croatia.

The FDA is investigating how the problem occurred. Burlington said it appears to be related to Medcomp changing the materials and design of its catheter systems last October.

Medcomp began getting reports of patient injuries in February, and on Tuesday notified its distributors to recall the devices. The FDA on Friday upgraded the recall to its highest priority.