Heamodialysis Risk --- Catheter (perma-cath) & Blood Clot

Friday  2014-9-19

Heamodialysis access -- the shape of a catheter and the formation of blood clot

After dialysis if one smashes the caps on both end of a used dialyser, at the arterial side one very often will find a blood clot about 2cm in length half clear whitish and half dark blood red whose shape fits exactly the inside of the catheter that goes inside the patient’s body with the whitish part fits the tip end; at the venous end of the dialyser a clot is rarely found and if there were any, the clot is generally small which doesn’t resemble any particular thing or shape.

The part of the catheter that goes inside a dialysis patient’s body is a plastic tube, within which a plastic wall divide the round lumen into 2 semi-circular shaped tunnels with the partition wall in the middle extending all the way out of the lumen at the tip by about 3mm. At the end bit, the 2 semi-circular tunnel walls are cut diagonally making two 1cm slant openings, another centimetre down there are 2 diamond shaped small holes appear 180 degree apart, one at one corner of the 2 tunnels.

Whether the catheters are locked with 5000 unit in 5ml strength Heparin or 25000 unit in 5ml, in fast or slow push make no difference to the clot formed or not. The difference of fluid movement at the tip of the tube inside a patient’s body, the area around the 4 openings of the end bit of the catheter made by human speed in pushing in saline and heparin is negligible.

The heparin inside the lumens beyond the diamond holes downward is relatively stable, unless the patient moves vehemently and vigorously with force or bend downward which may lead to blood being filled into the entire lumen even tint the out of body catheter pink or dark red. For safety reason, when the catheter is dark, better relock again immediately.

How does the fluid inter-react with one another at the area around the tip end where the 4 openings are, is beyond me. One thing is clear with these many holes fluid at this segment is murky, heparin if there were any would be diluted. As it is mostly are blood which surround the 4 holes, I would say 

heparin has no chance at this last 2 centimetres of the tube where riddled with holes. Most of the time, the clot will always occur at this end of the catheter beyond the diamond hole.

With unlock the clot can be drawn out some times, other times the clot when not drawn out will simply end up at the arterial side of the dialyser. If the clot can be drawn out, I would use this side as venous, this way, I am sure the other clot if there were any would be caught eventually by the dialyser.

             

If both catheters are smooth and without sucking I would be worried as I have seen a clot in almost every dialyser. However the fact that I am still here today after a year on catheter it is more of a puzzle for me rather than a risk.

The nurses’ standard practice is if a clot is drawn out, they would further draw out another 3ml of blood which I fail to see the reason in doing so.