Minimal volume of local anesthetic required for an ultrasound-guided SGB.

Background:  Compared with the blind technique, ultrasound-guided stellate ganglion block (SGB) reduces the amount of local anesthetic needed for a successful block. The purpose of this study is to determine the minimal, optimal volume of local anesthetic required for successful ultrasound-guided SGB and to reduce its adverse effects.

Methods:  Thirty-five patients with postherpetic neuralgia and complex regional pain syndrome of the upper extremity and the facial area were selected. For ultrasound-guided SGB by subfacial method, each patient was injected with 0.5% mepivacaine mixed with contrast media in 2 mL, 3 mL, and 4 mL doses at 2-week intervals. After the procedure, the spread of contrast media in the spine was checked by fluoroscopy. Ptosis and conjunctival flushing were rated and recorded. Adverse effects, such as hoarseness, foreign body sensation, swallowing difficulty, and upper arm weakness, were also recorded.

Results:  Out of the 35 initial patients, the results for 33 patients who received all three SGBs were included in this study. The contrast media spread to 4.80 ± 0.82, 4.94 ± 0.86, and 5.09 ± 0.97 total spinal segments in the 2 mL, 3 mL, and 4 mL groups, respectively. The cephalad spread of contrast media was 2.16 ± 0.74, 2.23 ± 0.85, and 2.30 ± 0.78 spinal segments for the 2 mL, 3 mL, and 4 mL groups, respectively, and the caudad spread of contrast media was 2.64 ± 0.51, 2.70 ± 0.61, and 2.89 ± 0.64 segments in the 2 mL, 3 mL, and 4 mL groups, respectively. There were no significant statistical differences in any segments for the three groups (P > 0.05). Review of the fluoroscopic images showed spread of the contrast media below the C7-T1 junction in all three groups. Ptosis developed in all three groups after the procedure.

Conclusion:  In conclusion, when performing an ultrasound-guided SGB, 2 mL dosage was sufficient for a successful block as the previous, conventional volume. Therefore, when performing an ultrasound-guided SGB, we recommend the 2 mL dosage of local anesthetics for a successful block.