can someone explain dialysis grafts to me?

There are two flavors of permanent dialysis access:

AV fistula:
A surgeon plugs a suitable forearm vein into either the brachial, radial or ulnar artery (e.g. a Cimino Brescia fistula). After a couple of months of high blood-flow through this vein, it will balloon out enough to resist getting poked every other day.

Upside: With good care, these can last forever (as long as the patient on dialysis, up to 10-15 years).

Downside: With poor care (GED level dialysis techs instead of RNs), they last a couple of weeks. Also, after placement they have to 'mature'. That means the patient needs a perma-cath or other temporary access for the 3-4 months it takes to mature.


AV graft:
A sugeon implants a piece of fancy gardening hose (rippled porous PTFE tubing) that is 4mm in diameter at one end and 7mm diameter at the other between one of the forearm (or if necessary leg) arteries and the vein.

Upside: With good care these last 3-4 years. Graft can be accessed after the initial surgical wounds have healed (2-3 weeks). So a patient can live on an IJ line (e.g. a Marhurkar) until the graft is ready.

Downside: With poor care (GED level dialysis techs instead of RNs), they last a couple of weeks. Different from native fistulas, the implant can get infected creating a major mess. Also, they tend to require maintenance. After 18months/2 years, they typically develop a stenotic region at the venous anastomosis which either requires surgical revision or interventional treatment.


Hope this helps.

As for temporary access:

Untunneled dialysis catheters:

Big ole central line (11-15Fr) in whatever vein you can get it into. Different sites, different troubles. Femoral (likes to get infected), subclavian (likes to f-up the vein precluding placement of a fistula later on) or IJ (higher infection risk than subclav due to drool and food residue, sticks out under shirt collar, not so great for people who have to go to work).
Note to intern of sub-I: If someone tells you to pull a temporary dialyisis catheter A. make sure it really has to come out B. make sure you know what you are doing (a 15Fr hole in the IJ can suck air killing the patient if you don't know what you are doing).

Cuffed tunneled dialysis catheter:

The real 'Perm-A-Cath' is an extra-long 13-15Fr central line that is tunneled under the skin for 10-12cm before it makes a turn and either enters the IJ, subclavian, femoral vein or IVC. It also has a 'cuff' that is usually made from Dacron and bonded to the (usually PU) catheter. After a week or two fibroblasts grow into the dacron forming a good shield against bacteria migrating along the catheter. It also makes a good mechanical bond (anyone who had to take one of these out before can appreciate this).
These perm-a-caths are completely at the grace of the dialysis staff that handles them. If they are half-way intelligent people who care about the patients (a rare trait in commercial dialysis mills), they will change the dressings, remove glue residue, clean the catheter with approved cleaning solution (using certain solvents on PU will remove the softeners and make the catheter brittle). If they are the usual commercial dialysis center dimwits, they will just slap on a new dressing with every dialysis run and let the glue pile up on the catheter (creating a perfect breeding ground for gram+ bugs).
A perm-a-cath can last 2 years if properly cared for. At some point the hubs will crack or a fibrin sheath will form around the tip disabling the catheter (for some of the perm-a-cath brands you can get a 'fix-it' kit that allows you to replace the hubs. A fibrin sheath can be stripped).
Note to intern or Sub-I: If someone tells you to pull one of these, make sure you know what you are doing. It is not rocket science, but it helps to have seen it done once before you endeavor on this yourself. Remember, the hole in the vein is 10-12cm from the skin entrance site. So this is where you want to compress when the red nile comes at you.

Thank you f_w. Very helpful.

f_w said:

Note to intern or Sub-I: If someone tells you to pull one of these, make sure you know what you are doing. It is not rocket science, but it helps to have seen it done once before you endeavor on this yourself. Remember, the hole in the vein is 10-12cm from the skin entrance site. So this is where you want to compress when the red nile comes at you.

Click to expand...

Also - and our team this month learned this the hard way - if you have a patient on the floor with one of these, don't let the nurses touch it. Because the dialysis techs lock the caths with an insanely high concentrations of heparin, then suck it out before each use. So if the nurse flushes it like it's a regular ol' IV, the patient gets a huge heparin bolus he didn't ask for.

Hurricane said:

Also - and our team this month learned this the hard way - if you have a patient on the floor with one of these, don't let the nurses touch it. Because the dialysis techs lock the caths with an insanely high concentrations of heparin, then suck it out before each use. So if the nurse flushes it like it's a regular ol' IV, the patient gets a huge heparin bolus he didn't ask for.

Click to expand...

Depending on the dialysis center, these lines get either locked with 100 IU/ml, 1000 IU/ml or 10.000 IU/ml heparin. So, you have probably done the math, a longer perm-a-cath can contain 35.000 IU of heparin....
(there is not too much science for the higher concentrations, I haven't looked up the literature but in my experience 1000/ml works just fine).

The other thing to remember when you pull out a tunneled line: Take the heparin out and then flush it back and forth with saline a couple of times. Heparin 'sticks' to the plastic (or probably to the fibrin covering the plastic). So if you pull the line, you can 'lace' your tract with quite a bit of heparin. Good luck obtaining hemostasis !

(btw. I would rather not have the intern touch these. the RNs typically have quite stringent policies in place on how to access various lines.)

So which one is the vas-cath I hear about? Is this where the dialysis catheter where a central line can go?

glorytaker said:

So which one is the vas-cath I hear about? Is this where the dialysis catheter where a central line can go?

Click to expand...

I believe it is just another brand of the tunneled cuffed variety.

I just finished my nephrology rotation and f_w seems right on. Might as well include peritoneal dialysis catheters for good measure.