Does chronic warfarin cause increased blood loss and transfusion during lumbar spinal surgery?

Abstract

The use of oral anticoagulation therapy such as warfarin is projected to increase significantly as the population ages and the prevalence of cardiovascular disease increases. Current recommendations state that warfarin be discontinued before surgery and the international normalized ratio (INR) normalized. To determine if stopping warfarin 7 days before surgery and correcting INR had any effect on intraoperative blood loss or the requirements for blood product transfusion. This was a retrospective cohort study in a high-volume tertiary care center. Sample comprised 263 consecutive patients who underwent elective lumbar spinal surgery. The outcome measures were intraoperative blood loss, intraoperative blood transfusion, postoperative blood transfusion, and the number of blood products transfused. The records of patients undergoing elective spinal surgery were analyzed for patient demographic data, comorbidities, coagulation panel laboratory findings, operative characteristics, blood loss, and blood transfusion requirements. These included patients undergoing full laminectomies with or without posterolateral fusion and instrumentation. Patients on warfarin were analyzed for the mean dosage of warfarin and underlying pathology that required anticoagulation. All patients on warfarin had their anticoagulation therapy stopped 7 days before surgery and their INR checked preoperatively to confirm normalization. Both univariate and multiple linear regression analyses were performed. The patients on warfarin had a mean intraoperative blood loss of 839 mL compared with 441 mL for patients not on warfarin (p<.01). Multiple regression analysis determined that warfarin and number of spinal levels decompressed/fused/instrumented were predictors for increased blood loss (R(2)=0.37). Patients on warfarin also had increased postoperative blood transfusions (23.1% compared with 7.4%, p=.04). There was no significant difference between groups in terms of intraoperative blood transfusion or number of units transfused. Patients on chronic anticoagulation therapy with warfarin who have their therapy stopped 7 days before surgery and have their INR normalized still demonstrated increased intraoperative blood loss and requirement for postoperative transfusion. Surgeons should be aware of the increased propensity of these patients to bleed despite adherence to protocols and should attempt to mitigate this risk.