Here is a question from my friend and colleague Kathleen Finnegan, MS MT (ASCP )SH, Chair of the CLS program at Stony Brook University, New York. This question was posted to the ASCLS Consumer Web Forum through Lab Tests Online: “In the procedure room setting (cardiac catheterization or EP lab) what is the standard length of time to wait to check the activated clotting time (ACT) assay after a heparin bolus is given?”
Hi Kathleen, I don’t have direct experience with the ACT in the catheterization lab or during bypass surgery. I have always assumed that the anesthetist/anesthesiologist performs the ACT whenever heparin is running in response to the immediate needs of the surgeon, such as just before administering protamine sulfate and again just after. The standard scheduled use of the activated partial thromboplastin time (PTT) doesn’t help, as in this case the specimen is supposed to be collected 4 hours or more after the initial bolus dosage and within 24 hours of starting standard dose heparin. This doesn’t apply to the whopping doses used in surgery, and I am not sure whether heparin is started with a bolus in surgery. I invite responses from any anesthetist or anesthesiologist who may monitor this site. Geo.
Kathleen, I contacted my friend and colleague Derek Webber, University of Alabama at Birmingham, who is a surgical physician assistant. Derek checked with some friends and received these answers:
From a chief anesthesia resident: I don’t know the official answer, but before we go on bypass, we normally draw a sample for an ACT 2 minutes after we give a bolus of heparin. We also always notify the vascular surgeons 2 minutes after we give a heparin bolus, before they start working with the vessels. Normally 2 min is the cut off, but there may be more practices out there. I hope this helps.
The second message is from a PA who has worked in CV surgery for the past year: We give our heparin as a bolus, weight based, usually 30–40K. Usually we check ACT ~3 min after the bolus. Half life is 1.5 hr so it’s about 6 hrs before its all out, anesthesia will re-dose as needed based on ACT throughout the case as directed by perfusion. We really only care about ACT before we go on pump or after protamine, rarely will the surgeon want to know what’s the ACT during the pump run.