Abstract W P366: Hypothermia Does Not Affect Tissue Plasminogen Activator Activity in Acute Ischemic Stroke Patients as Measured by Thromboelastography

Abstract

Background: Currently, t-PA is the only FDA approved treatment for acute ischemic stroke (AIS). Supplementing t-PA with therapeutic hypothermia is being evaluated, but cooler temperatures may affect the enzymatic activity of t-PA. Thromboelastography (TEG) determines coagulation status in whole blood, and has detected hypercoagulability in AIS patients compared to healthy controls. Using TEG, we evaluated the effect of variable degrees of hypothermia on clot formation and lysis in AIS patients receiving t-PA. Methods: Between June 2012 -July 2013, venous blood from 18 AIS patients receiving t-PA within 4.5 hours of symptom onset was collected prior to and 10 minutes after t-PA bolus. Blood samples were analyzed by TEG at 30°C, 33°C, and 37°C. The variables of interest were R (initiation of clot formation), K (speed of clot strengthening), Angle α (rate of clot formation), and LY30 (percentage of clot lysis over 30 minutes) (see figure). All statistical analyses were performed using SAS 9.3. Results: Baseline R averaged 6.0, 5.6, and 4.6 minutes at 30°C, 33°C, and 37°C (p=0.02),K averaged 2.5, 2.3, and 1.4 (p=0.01),and Angle averaged 59.1, 62.4, and 69.3(p=0.01), indicating slower clotting at lower temperatures. Post t-PA LY30 averaged 93.9, 93.9, 89.8 (p= 0.61, N=18) indicating no effect on t-PA lytic activity at lower temperatures. Conclusions: Our data suggest that hypothermia progressively slows clot formation in AIS patients but has no effect on the lytic effect of t-PA as measured by TEG.