Quote from sueinga
We draw our monthly and midmonthly labs from the arterial lumen of CVC patients and normally first withdraw the indwelling heparin of course- at least 3ml- 5ml
There has been a debate as to whether the P.T./INR would be accurate anyway if drawn the same way or if a peripheral stick should be done. My latest instructions are get the pt on the maching and draw from the arterial port on the blood tubing---any opinions?
Draw it from the blood tubing once the pt is on? And has received heparin*? How could this be accurate?
When I worked in a clinic, we of course always withdrew the indwelling heparin first (3 cc syringe); after that, we drew every other lab; then we withdrew an additional 30 cc of blood in 3 10-cc syringes; after that, we drew our PT/INR tube. Finally, we reinfused the 30 cc of blood into the pt. Yes, it's a lot to keep up with (having to keep the syringes with the blood sterile, of course), but was considered to give accurate results.
*And if the pt hasn't received the loading dose of heparin, then s/he hasn't been properly heparinized before tx! Not trying to state the obvious, just to make a point.