Inclusion Criteria:  Adult patients over 18 years of age undergoing cardiac surgery under general anesthesia  Exclusion Criteria:  If the patient already has an arterial catheter and does not need additional arterial cannulation. When arterial cannulation is performed on an artery other than the radial artery due to the surgical technique or the patient's condition. When the patient's condition is urgent, such as emergency surgery, and there is no time to proceed with the research.