Vitamin B12 and Folate Administration on Homocysteine Concentrations After Nitrous Oxide Anesthesia

Patients will be randomized into the following arms: * Arm A: patients will receive N2O (60% N2O/40% O2) in an open-label fashion during surgery and vitamin supplementation (vitamin B12, 1 mg, and folate, 5 mg) before surgery. * Arm B: patients will receive N2O 60% N2O/40% O2) in an open-label fashion during surgery and placebo before and after surgery. * Arm C: patients will not receive N2O, vitamin supplementation, or placebo during/before surgery. Patients in this arm will not be randomized. Patients will have blood drawn (total of 1-2 teaspoons over 3 days). We will take these samples before their surgery, when their surgery is completed, and in the morning of post-operative day 1. We will be checking their troponin I and troponin T, homocysteine, Vitamin B12, and folate levels. We will also perform a 12-lead EKG. Before and after surgery for patients in Arm A or B, will receive either vitamin B12 (1 mg) and folic acid (5 mg) (or placebo) added to their IV infusion. We also plan to use a non-invasive test known as a nerve conduction study to measure the function of their nerve system. Briefly, 2 small electrodes are attached to their skin over a nerve and, like an EKG, faint electrical pulses are generated and recorded. A typical nerve conduction measurement lasts about 10 minutes. After the patients surgery we will do genetic testing of MTHFR genotype. All study samples have been collected. Of note: there were no secondary outcomes.