Patient-perceived duration of effect of lidocaine and bupivacaine following diagnostic medial branch blocks; a multicenter study.

Objective: To quantify the duration of pain relief reported in association with lidocaine and bupivacaine in patients suffering from axial back pain, who reported a response of ≥80% relief lasting at least 30 ​min following medial branch blocks(MBB). Design: A retrospective review. Methods: Setting & Subjects: Four academic medical centers utilized a uniform pain diary. It was administered to consecutive patients after undergoing MBB. This pain diary included NRS pain score and percentage of pain relief (PPR) at 12 designated time points. Results: One hundred and fifty pain diaries were collected and analyzed. 42 blocks were performed in the cervical spine, 7 in the thoracic spine, and 101 in the lumbar spine. By NRS, 32% of pain diaries indicated that the patient experienced ≥80% pain relief at the 30-min and 42.7% (64/150) did so by PPR. Mean duration of ≥80% pain relief as measured by NRS in the bupivacaine subgroup was 3.5 ​h (SD 8.7, 95% CI 0.6-6.5) versus mean duration of 16.4 ​h (SD 19.6, 95% CI 5.4-27.4) in the lidocaine subgroup. Mean duration of ≥80% pain relief as measured by PPR in the bupivacaine subgroup was 19.2 ​h (SD 19.2, 95% CI 13.3-25.1) versus mean duration of 12.2 ​h (SD 15.9, 95% CI 5.6-18.8) in the lidocaine subgroup. Conclusions: This study demonstrates that there is no discernable or statistically significant difference in the duration of effect when comparing lidocaine to bupivacaine in patients that experience 80% or more relief following a medial branch block. This data suggests any emphasis on concordant duration of relief from specific anesthetics utilized for diagnostic medial branch blocks should be reconsidered.