INR is commonly used to guide heparin use in many clinical situations. I just want to know the reason why ACT is chosen during CPB. Why not INR?
because inr is unreliable in such operations,due to the high doses of heparin that we usually administer
Unfractionated Heparin dosage is usually monitored by APTT while INR is used for monitoring warfarin therapy. But in case of blood flow in extracoropeal circuits like CPB , ECMO or hemodialysis ..testing for ACT is more accurate due to the high doses of heparin given to prevent blood clotting in that synthetic circuits . A great informative site regarding the history of using the test, , method, normal values , factors that affect it and needed values for extracorporeal circuits are presented in that nice website.Best wishes.
http://www.practical-haemostasis.com/Miscellaneous/Miscellaneous%20Tests/act.html
And last but not least measuring of ACT is easier and faster than PTT.
But be careful: ACT and PTT results are not interchangeable. In the area where they overlap they have a poor correlation. ACT should be prefered when you are treating with or monitoring high doses of heparin.
ACT is easier and faster to be calculated than aptt-inr.
Moreover, mechanisms of action of heparin and warfarin are different and this requird different
ACT is much easier to calculate by the machine in a short time while INR takes longer time . Also ACT and APTT MEASURE THROMBIN EFFECT of heparin while INR measure vit k depend factors
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