The anesthesiologist who performed the LPBs and SNBs was strictly blinded to the patient's group assignment before the procedure. Only when the anesthesiologist commenced with the block was a prepared sealed opaque envelope containing the patient's group assignment opened. Then the anesthesiologist completed the block with the indicated technique. There were two investigators in the study. One investigator blinded to the technique used was present in the block area to assess the procedure-related outcomes. To ensure blindness of the patient to the method, all procedures performed behind an opaque screen and investigators were required not to say anything about the technique in use. Another investigator assessing the block quality was blinded to the group allocation and remained outside the block area until completion of the procedure. Finally, a statistician blinded to the entire process performed the statistical analysis, with group data labelled only as numbers until all analyses were completed.
BMC Anesthesiol. 2019;19(103) © 2019 BioMed Central, Ltd.