Background and Objectives. Clinical evidence suggests that stellate ganglio
n block (SGB) might modulate the immune system. Little is known, however, a
bout the immunologic effects of SGB. We examined how SGB affected immune fu
nctions by analyzing the activation response of lymphocytes during SGB. Met
hods. Twenty-four volunteers were randomly subdivided into three groups. Th
e SGB group (SGB; n = 9) received 6 mt 1% lidocaine at the sixth cervical v
ertebra (C6) transverse process and showed Horner's sign and elevation of i
psilateral facial and upper limb temperature. The lidocaine group (n = 7) h
ad 6 mt 1% lidocaine injected into subcutaneous tissue at the neck and show
ed no remarkable clinical effects. The saline group (placebo; n = 8) receiv
ed 6 mt saline solution injected at approximately the CG transverse process
and showed no remarkable clinical effects. Peripheral blood samples were d
rawn before and 30 minutes after drug administration. Samples were incubate
d for 4 hours under the stimulation of mitogen. Using now cytometry, we mea
sured the ne nova expression of CD69, which is one of the initial markers o
f lymphocyte activation and which reflects the cell activation process. The
changes in pre- and post-values were calculated and compared among the thr
ee groups. results. In only the SGB group, the helper T-cell activation was
significantly reduced, and the cytotoxic T-cell activation also tended to
decrease after SGB. Conclusions. SGB may depress immune system activity for
a short time, as reflected in the T-cell activation response.