Sara Cheng, MD has left the University of Colorado and we have closed this study.

This study plans to learn more about the role of 2 blood tests in predicting who might develop a blood clot in their arm or leg after major surgery. The investigators know that patients who have cancer and major surgery have a higher than normal risk of getting blood clots in the veins of their arms or legs. This can be very dangerous because the clot can move into your lungs.

Venous Thromboembolism (VTE) after cancer surgery hospitalization is the most common cause of death at 30 days after cancer surgery, and is a significant source of patient morbidity and health care cost. Pharmacoprophylaxis has proven efficacy in preventing post-discharge VTE in surgical cancer patients, but perceived risks and costs pose barriers to widespread adoption by clinicians. Risk stratification of this patient population is necessary to allow appropriate prescription of prophylaxis to the highest risk patients. Can the investigators develop a risk stratification model that includes a readily available laboratory test, the thromboelastogram with or without platelet mapping?

Inclusion Criteria:

• subjects who are having primary, open resection surgery of gastrointestinal or bladder cancer

Exclusion Criteria:

• currently receiving anticoagulation therapy
• pregnant