Background and Objectives: The purpose of this study was to assess the radiographic and clinical distribution of 1 to 4 paravertebral injections by use of the same total volume of local anesthetic mixture.

Methods: Sixty-nine patients scheduled for surgical interventions suitable for bilateral PVB were included in the study and were randomly assigned to 1 of 3 treatment groups. Group 1 received 4 paravertebral injections on one side versus 1 injection on the contralateral side (23 patients), group 2 received 4 injections versus 2 injections (23 patients), and group 3 received 4 injections versus 3 injections (23 patients).

Results: Sixty-one patients were included in the final analysis, which resulted in 368 thoracic paravertebral injections. Overall, 97% of the patients had adequate loss of sensation within the targeted area at the side of 4 injections, compared with only 11% for the single injections. The average vertical spread of contrast was found to be significantly greater in the set of 4 injections, with mean (SD) 6.5 (2.01) dermatomes, compared with the single injection, with 3.0 (1.19) dermatomes (P < .05). The average vertical spread of contrast and complete absence of sensation were significantly greater in the set of 4 injections compared with the set of 2 and 3 injections (P < .05).

Conclusion: The main finding of the present study was that multiple paravertebral injections resulted in more reliable radiographic and clinical distribution compared with a single-injection technique.