Tuesday, December 14, 2010

PD: Catheter outflow failure

I recently saw a patient in our peritoneal dialysis clinic who had been ultrafiltering about a liter a day but who was now consistently draining 100ml less than his instilled PD solution volumes despite extended drain times and multiple acrobatic contortions to try and recover additional fluid.

Peritoneal catheter outflow problems are common and many PD patients transfer to hemodialysis because of catheter related issues. Peritoneal outflow failure can be defined as the incomplete recover of instilled dialysate consistently within 45 minutes of beginning a drain.

So what are some of the things you can do when faced with a PD patient who is having difficulty recovering their dwells? Recently, an article in AJKD reviewed the topic and the salient points are outlined below.

1) Check for peritonitis – Start by looking for signs and symptoms then look at the dialysate to see if it’s overtly cloudy followed by a dialysate cell count and culture. During episodes of peritonitis the permeability of the peritoneal membrane to water, glucose and proteins is increased. This leads to rapid loss of the osmotic gradient as glucose moves from the dialysate into the blood resulting in reabsorption of fluid if dwell times are long enough.

2) Check a KUB – Useful for many reasons. The KUB can help you see catheter kinking, tip migration and constipation, which is very common culprit of outflow obstruction.

3) Examine the patient for signs of catheter leakage – Pericatheter leaks usually show up soon after catheter placement as wetness on the exit site dressing. Leakage of dialysate can also occur at any time into the abdominal wall, the pleural space (usually the right) and the genitals.

4) Is there resistance to dialysate or saline instillation? – If it’s tough getting fluid in in addition to getting fluid out something inside or outside the catheter is blocking it up. Inside kinks (which you might have seen on the KUB), fibrin and blood clots are potential culprits. Outside dilated stool filled intestine, and other intrabdominal organs in particular the omentum may be occluding the catheter. If fluid flows freely in, and the above options have been ruled out ultrafiltration failure should be considered.

In our patient, exam was unremarkable apart from trace lower extremity edema and saline was easily instilled into the peritoneal dialysis catheter by one of our RNs. The recovered PD dialysate was clear and cell count was zero. A KUB showed stable catheter position without kinking and copious stool. We started a trial of laxatives and were gratified to hear a few days later that our patient was now achieving his former ultrafiltration volumes.

4 comments:

Michelle said...

As a dialysis patient (PD), we are taught that if you do not have a daily BM, consider yourself constipated - which can cause the decrease in fluid withdraw. Personally, I find when I am dehydrated, my drain volume is considerably lower, but not to the point of a negative number.

Thanks for the interesting info on this site.

Graham Abra said...

Excellent point about the importance of bowel regularity for PD patients Michelle. I've been amazed at how even seemingly mild constipation can impact PD.

Francesco Iannuzzella said...

1, 2,... 4 Do not forget (5), i.e. thrombolytic agents.

In Europe, we routinely use heparin as a first choice in any case of unexplained outflow failure and, if ineffective,we add a thrombolytic agent. In my experience, urokinase 5,000 UI in NS 40 mL may be injected into the catheter as a locking solution for no more than 20-30 min. Two, three attempts with increasing urokinase doses (up to 50,000 UI or even more) may be necessary.

Graham Abra said...

Good point Francesco. A similar empiric approach is also often used at our center in the United States. I liked that the AJKD article suggested a more diagnostic approach to things but I would feel silly missing fibrin or blood clot that was maybe acting as a one way valve valve and causing no problems with instillation.