Answer to Question #301581 in Human Anatomy and Physiology for Rawan

Question

 These two questions about anesthetizing a rabbit

1.How does the coagulation time of the test tube with heparin change? Why?

2. How does the coagulation time of the test tube with Lung tissue immersion liquid change?

Answer 1

a) The ACT is a bedside test of coagulation that measures the time to clot formation in whole blood that is activated by either celite or kaolin. The celite or kaolin activates the contact activation pathway, and, thus, the ACT measures the function of the enzymes and inhibitors in that pathway.

b) The normal range for ACT is 107 ± 13 seconds.²⁵ Predictably, the ACT is prolonged in the presence of heparin. Prolongation of the ACT in response to heparin is fairly linear at heparin concentrations > 1 U/ml, and observational studies demonstrate that it is an effective monitor for adequacy of heparin anti-coagulation during CPB. However, it is insensitive to heparin at lower concentrations, including concentrations in the therapeutic range, Therefore, return of the ACT to baseline after protamine administration does not ensure that heparin is entirely neutralized.²⁶ Conversely, thrombo-cytopenia, hemodilution, hypothermia, and circulating non-heparin anticoagulants can also prolong the ACT. Therefore, prolongation of the ACT does not necessarily diagnose residual heparinization.