Heart Rate Variability (HRV) to Evaluate Surgical Risk on Patients on Beta Blockers

Beta blockers have been shown to decrease the risk of intraoperative cardiac events in patients at high cardiac risk. However, they have also been associated with side effects (for instance, stroke.) The role of beta blockers in patients at intermediate cardiac risk undergoing surgery is controversial. Heart rate variability is a way of evaluating the cardiac function of a patient. Decreased heart rate variability is associated with early cardiac death in patients with congestive heart failure (CHF) and after a heart attack. It has been shown to transiently decrease in patients in hemorrhagic shock after trauma and returns to normal after resuscitation in trauma and burn patients. The investigators hypothesize that beta blockers will maintain pre operative heart rate variability in patients with intermediate risk of cardiac events during operative intervention with laparoscopic surgery.