Randomization and Blinding
Eligible patients were randomly allocated in a 1:1 ratio to either continuous SAPB Group L or Group H. Allocation sequence was created by a computer-generated list. Allocation concealment was implemented by using sequentially numbered, opaque, sealed envelopes. Block randomization was performed with a 1:1 allocation ratio by fixed block size. The drug concentration was assigned by specialized staff, and the user, follow-up personnel, and patients were not informed of the grouping. The data analysis was performed by independent research staff who did not inform the group assignment.