All patients will be monitored with pulse oximetry, non-invasive blood pressure and five leads electrocardiography (leads II and V5). A radial artery catheter and a central venous catheter will be placed under local anesthesia before induction. On-screen pressure tracing will be used to determine end-expiration, and the CVP will be averaged over three respiratory cycles to eliminate respiratory artifacts. All staff in the operating room will be unaware of the randomization code.