2.3 Patient grouping and randomization
Patients undergoing modified radical mastectomy were randomly divided into three groups. The patients were randomly allocated into three groups based on a computerized randomization table created by a researcher who was not involved in the study. The researchers randomly assigned an ID card to each registered patient, each of which was sealed in an opaque envelope3. The nerve block technique was performed by another anesthesiologist who was completely unaware of the patient’s ID. None of the patients knew the specific grouping. a blind anesthesiologist(AIU), used the patient’s ID, to collect data In the breast surgery ward. Surgeons, attending anesthesiologists, outcome evaluators and data analysts do not know the specific grouping.