Abstract 384: Monitoring of Preoperative Anticoagulation Status in Post-PCI Patients on Warfarin Undergoing Non-Cardiac Surgery: Risk of Major Adverse Cardiac Events and Transfusion

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Background: There is limited data on an optimal approach to preoperative INR screening in patients prescribed warfarin, with current guidelines lacking definitive recommendations on timing or need of INR assessment. Outcomes for these patients are largely unknown. Accordingly, we describe rates of pre-operative INR testing rates and its association with postoperative major adverse cardiac events (MACE) and transfusions among post-PCI patients on warfarin undergoing non-cardiac surgery (NCS). Methods: We identified all post-PCI VA patients undergoing NCS from 2004-2011 who were prescribed warfarin. Among these, we assessed rates and results of INR assessment (>1.5, ≤ 1.5, or unknown) within 5 days of NCS. We measured the association of INR status with 30d MACE and post-operative RBC transfusions, using multivariable regression analysis to adjust for cardiovascular and operative risk factors. We also adjusted for the use of perioperative bridging therapy with heparin products. Results: Among 1,357 post-PCI patients on warfarin undergoing NCS, 534 (39.3%) had an INR drawn within 5 days of surgery. INR was high (>1.5) in 166 (31.1%) and low (≤ 1.5) in 368 (68.9%). Unadjusted MACE rates were similar between those without an INR (5.3%), with a low INR (8.2%), and with a high INR (6.0%) (p-value = 0.17). PRBC transfusion was higher in those with a high INR (17.5%) compared to low (12.5%) or no INR (9.5%) (p-value=0.008). After adjustment, MACE was significantly associated with ESRD, prior MI, use of bridging therapy, and inpatient surgery status, but not INR status (Table). PRBC transfusion was associated with a high INR (OR 3.95, CI 1.91-8.17) and use of bridging therapy with heparin (OR 1.81, CI 1.07-3.05). Conclusions: Strategies for monitoring and managing cardiac patients on warfarin are heterogeneous in the pre-operative period, with nearly half of patients undergoing NCS without pre-operative INR evaluation. The presence of a high INR value predicted pRBC transfusion, but not MACE. Our study suggests a role for pre-operative screening of INR in patients on warfarin to assess risk for post-operative bleeding.