Bioequivalence and Bioavailability Forum

Dear Mittyri,

I'll only answer the second part of your post, as Helmut already answered the first.

❝ 2. During the sampling a nurse inject little volume of heparine solution to catheter after each blood draw. To avoid the contact of heparin solution and vacutainer the nurse takes away little volume of blood before each next blood drawing.

❝ What do you think? Is it really necessary to remove 'heparinized' blood from the catheter?

That's indeed the standard practice, in order to avoid diluting the plasma sample with the heparinised saline contained in the void volume of the catheter (though the dilution factor would be rather limited). Could also avoid issues in the bioanalytical phase.

I see one more advantage: when removing this small volume of blood you can ensure that the catheter is not blocked. It gives a few more seconds to try and unblock it, or to switch to plan B, without delaying the sample too much.