Another common access challenge is blood clotting, also called thrombosis.

Your blood has clotting cells called platelets. Platelets stick together to seal off damaged blood vessels, like a cork seals up a bottle. Forming clots is their job. The problem is, platelets also stick to scar tissue and damaged blood vessel walls in a fistula or graft. And, of course, every needle puncture causes a little bit of damage.

Everyone on HD gets needle sticks, but not everyone gets a clotted access. Why not? Usually, because damage to the blood vessel isn't enough. To form a blood clot, blood must also be moving slowly through your access. And this is something you can help prevent. The chart on page 8-19 will tell you how.

If a clot is not treated, it can seal off a fistula or graft so no blood can go through it. The fistula or graft will need to be repaired before it can be used. Sometimes repair is not possible and replacement is needed.

Grafts are much more likely to clot than fistulas. Your own blood vessels have smooth linings that resist clots. No graft material now exists that can stop clots as well as your own blood vessels.

Stenosis—narrowing of your blood vessels—happens slowly, but clotting can happen very quickly. So it's important for you to know the major warning sign: your thrill slows or stops. If you notice no thrill, tell your doctor or nurse right away. If it is not a dialysis day, call the after-hours number for your dialysis center. Thrombosis can often be treated with injected medication to dissolve the clot. It may also be treated with radiology or surgery.

Clotting is often a problem with catheters, too. Anti-clotting medication is left in a catheter after it is used. But even so, clots can block the tubing—like a clogged faucet. To fix this, medication is used to dissolve the clot, or the catheter may have to be replaced. Make sure the dialysis staff injects the medication quickly and in the right amount. Ask how much your catheter holds. The venous side will hold a little more than the arterial side.

Cause of blood clotting	What you can do
Stenosis	Find stenosis as early as you can by noting any changes in your thrill or bruit
Low blood pressure (much more likely with standard in-center HD than with daily or nocturnal HD	Tell your care team right away if you have low blood pressure during dialysis (this might include feeling lightheaded, dizzy, or nasueated)
Taking off too much fluid at dialysis	Avoid gaining too much fluid weight between treatments Know your fluid removal goal and dry weight Check the dialysis machine to be sure your fluid goal is set correctly If you gain real weight (not fluid weight), tell your care team so your dry weight can be adjusted
Putting too much pressure on the access or taking blood pressure readings in the access arm	Don't sleep on your access arm Don't carry heavy things across your access Don't wear a tight watch, bracelet, or elastic on your access arm Learn how to hold your sites safely after dialysis (no clamps) Don't let anyone take blood pressure readings, draw blood, or start IVs in your access arm
Wrong dose of anti-clotting medication (heparin or coumadin)	Know your medication dose and check to be sure that you are given the right dose