 Blood 15ml will be collected from an intravenous line placed after induction of anesthesia at four time points: 1 pre-tourniquet placement, 2 60 minutes following inflation of the tourniquet and 3 120 minutes after tourniquet inflation, and 4approximately 30 minutes following tourniquet removal. These specimens will be placed into Vacutainer tubes with no anti-coagulant. They will be labeled with study name, subjects study ID number, sample number 1, 2, 3, 4, and date. Bloods from the first three time points will be kept refrigerated until the final sample is obtained Intra-operatively additional doses of Fentanyl and doses of Labetalol and Hydralazine will be recorded. The use of a nerve block will be documented as well. 