Single-Injection Versus Multiple-Injection Technique of Ultrasound-Guided Paravertebral Blocks A Randomized Controlled Study Comparing Dermatomal Spread

Background and Objectives: The objective of this study was to investigate the extent of dermatomal spread following an ultrasound-guided thoracic paravertebral block (PVB) when equal volumes of local anesthetic are injected at 1 versus 5 vertebral levels. Methods: Seventy patients undergoing a unilateral mastectomy were randomized to receive either single or multiple injections of a PVB under real-time ultrasound guidance using a parasagittal approach. The patients in the single-injection group received a PVB at T3-T4 level with 25 mL of 0.5% ropivacaine and 4 subcutaneous sham injections. Patients in the multiple-injection group received 5 injections of a PVB from T1 to T5 level. Five milliliters of 0.5% ropivacaine was injected at each level. Evaluation of the sensory block was carried out 20 minutes following the completion of the PVB. Results: The median (interquartile range) dermatomal spread was not significantly different for the single-injection group (5 [4-6]) compared with the multiple-injection group (5 [5-6]), with a median difference of 0 segments (95% confidence interval, -1 to 0 segments; P = 0.22). The median time to performance of the single-injection PVB was shorter compared with the multiple-injection group (10 minutes), with a mean difference of -4 minutes (95% confidence interval, -6 to -3 minutes; P < 0.001). Conclusions: An ultrasound-guided single-injection PVB provides equivalent dermatomal spread and duration of analgesia compared with a multiple-injection PVB. The single-injection technique takes less time to perform and hence may be preferred over a multiple-injection technique. The trial was registered prospectively at ClinicalTrials.gov (NCT02852421) on July 15, 2016.