Coagulation status using thromboelastography in patients receiving warfarin prophylaxis and epidural analgesia.

To determine the coagulation status of patients receiving postoperative warfarin and epidural analgesia using thromboelastography (TEG(R)).Prospective, observational, clinical study.Orthopedic postoperative division at a university hospital.52 ASA physical status II and III patients undergoing knee arthroplasty and receiving prophylactic warfarin and epidural analgesia.Patients' preoperative and postoperative coagulation status was determined by TEG(R). Daily TEG(R) parameters were obtained until the epidural catheter was removed. TEG(R) parameters include reaction time (R-time or time until the first significant levels of detectable clot formation), K-time (clot firmness), maximum amplitude (MA-clot strength), alpha angle (clot development), and coagulation index (overall coagulation). In addition, daily international normalized ratios (INRs) were obtained as per our routine practice. On the day of catheter removal reaction time was significantly increased compared with preoperative values (p < 0.0001), but it remained within normal ranges. There was no change in the coagulation index. However, INR was abnormal and significantly increased (INR = 1.48+/-0.3; p < 0.0001), compared with preoperative values, on the day when the epidural catheter was removed. When the epidural catheters are removed, overall coagulation status, as measured by TEG(R), and despite an elevated INR (mean INR <1.5), remained within normal limits in patients receiving low-dose warfarin prophylaxis.