After how many minutes, according to the protocol of your department, it is advisory to sample blood for ACT after heparin dose administration before the commencement of CPB?
Hi Robert, I hope this paper will help.
http://www.amsect.org/sections/education/documents/PDF/Anticoag_ACTvsHemodilHypotherm.pdf
Hi Steingrimur,
thank you for your answer. I understand 5 minutes delay to evaluate heparin response curve, but how long time have I to wait for check the level of anticoagulation? I mean if the effect of heparin to anticoagulation is immediate or with delay?
Hi Robert, heparin response is not immediate. It first has to first bind to heparin-binding serum proteinase inhibitors (AT-III, HC-II) before the inhibitor-heparin complexes become efficient thrombin inhibitors.
http://pubs.acs.org/doi/abs/10.1021/bi00165a013
As said, 3-5min for i.v. bolus, but depending on the dose.
In lower concentrations you will not find any systemic (plasmatic) response, most of the low dose applied heparin will have its action at the endothelial cell layer of the vessels and result in no significant ACT change. Then you have wait for days (saturation), until you will see a ACT response. Binding to the endothlial cells is in part independent from the plasmatic ATIII etc binding.
In our clinical practice in vascular surgery, 10 minutes following administration 100U high molecular weight heparin per 1kg body mass.
After standard IV bolus heparin is given 3 complete cardiac out put over 3 minutes ( minute out put ) will mix this heparin with the blood evenly hence though the anticoagulation to IV heparin is immediate in those areas where heparin has mixed with blood I will wait at least 3 minutes to evaluate its maximum effect. Hence I feel the answer 3- 5 minutes after IV bolus dose is rationally acceptable.
Hi Robert,
I understand about 4-5 minutes delay to evaluate heparin response curve.
Once administered heparin has to mix with the blood completely and then trigger the augmentation of antithrombin and heparin cofactor II. In my opinion the effect should be obvious if you draw a post blood sample in 2-3 minutes and perform the ACT.
Even in invitro study if you place blood in a tube containing heparin, the effect you see is immediate. In order for the intravenously administered heparin to get completely mixed with the entire 5 litres of blood you at least require 2-4 cardiac samples and once it is mixed homogeneously with the blood it has to augment the activity of antithrombin and you may give another 1 minute so in about 2-3 minutes time there should be optimum ACT effect due to heparin.