Perioperative Kinetics of Reactive Hyperemia Using Noninvasive Digital Thermal Monitoring

Primary Objective: The primary objective of the study is to characterize and measure the impact of major surgery on the kinetics of endothelial function during the perioperative period. Reactive hyperemia, characterized by Digital Thermal Monitoring (DTM), will be utilized to characterize this during the perioperative period in patients undergoing major abdominal or thoracic surgery. This will attempt to characterize the relationship between impaired endothelial function, the extent of surgical insult, and the risk for adverse postoperative outcome. Secondary Objectives: Secondary objectives of this study will evaluate the following: * The incidence of major complications in correlation to reduced preoperative reactive hyperemia * The incidence of major complications in correlation to reduced postoperative reactive hyperemia (calculated as absolute value and as the change from baseline \[delta\]). * It is anticipated that two factors (namely, preoperative cardiovascular risk and the extent of the intraoperative inflammatory response) will predominantly contribute to the impaired microcirculatory/hyperemic/endothelial function and should therefore be accounted for in this study. The correlation between impaired reactive hyperemia and these two contributory factors will be evaluated. 1. Preoperative cardiovascular risk will be assessed using risk scoring systems that attempt to infer patient risk according to preoperative co-morbidities, namely The ASA Physical Status Classification System24, The Lee Modified Cardiac Risk Index,25 and The University of Texas M. D. Anderson Cancer Center Modifiers to the Lee Modified Cardiac Risk Index (an unvalidated scoring system that considers factors unique to the cancer surgical population), and The Metabolic Syndrome. The latter represents a larger at-risk patient population who has yet to develop symptomatic cardiac lesions (and therefore will not be identified by the Lee modified Cardiac Risk Index). 2. Intraoperative