Abstract 284: Association of Pre-Operative INR Evaluation with Risk of Major Adverse Cardiac Events and Bleeding Complications in Cardiac Patients Undergoing Non-Cardiac Surgery

Abstract

Background: Routine laboratory testing is common in pre-operative patients, independent of specific clinical indication. One example is routine INR checks in patients without prior anticoagulant use. However, its efficacy in detecting significant coagulopathy and reducing adverse outcomes is unknown. We describe the frequency of pre-operative INR testing in a cohort of post-PCI patients not on anticoagulation undergoing non-cardiac surgery (NCS) within the VA system, and associated adverse events.

Methods: We identified all post-PCI VA patients not prescribed warfarin undergoing NCS from 2004-2011 and determined the rates of INR assessment within 120 hours (5d) of surgery. We then measured the association of INR status (>1.5, ≤ 1.5, and unknown) with MACE within 30d and in-hospital bleeding events. We also conducted a secondary analysis excluding patients undergoing “low risk” operations, defined as eye, ear, or integumentary surgeries.

Results: Among 20,118 post-PCI patients undergoing NCS who were not on warfarin, 3,678 (18.3%) had a pre-operative INR check. Of those, 108 (0.5%) had INR > 1.5. Patients with INR > 1.5 were more likely to suffer MACE events than those with INR assessed but ≤ 1.5, or unknowns (16.7% vs. 5.5% vs. 3.4%, p<0.001). They were also more likely to have bleeding events (18.5% vs. 9.8% vs. 4.9%, p<0.0001). After excluding patients undergoing low-risk surgeries (n=5,739), these trends remained significant.

Conclusions: Among post-PCI patients not on warfarin undergoing NCS, nearly one-fifth had an INR checked pre-operatively. Both the presence of an INR test and an INR value >1.5 were associated with higher risks for both MACE and bleeding events, as compared to those patients without INR assessment. Our study shows that pre-operative INR testing in patients not on anticoagulants is relatively uncommon, and that testing, when it does occur, appears to be associated with higher rates of MACE and bleeding. Further research is needed to understand which patients without prior anticoagulation would benefit from pre-operative INR checks.