Background: Recent investigations suggest that the sympathetic nervous system affects the immune system. This study examined whether stellate ganglion block (SGB) affects the immune response, specifically the distribution of lymphocyte subsets and natural-killer (NK) cell activity.
Methods: Ten volunteers received three different treatments in random order at 7-day intervals: (1) SGB with 7 ml of 1% lidocaine; (2) an identical volume of normal saline injected at the same site as SGB; and (3) an identical volume of 1% lidocaine injected intramuscularly. Blood samples were drawn before and 30 min after treatment. The distribution of lymphocyte subsets was analyzed, and NK cell activity was measured. Plasma concentrations of epinephrine, norepinephrine, adrenocorticotropic hormone, and cortisol were measured.
Results: Any value in the normal saline and intramuscular treatments did not change significantly. After SGB, the plasma concentrations of epinephrine and norepinephrine decreased significantly (P < 0.01), but adrenocorticotropic hormone and cortisol values were unchanged. Increases were observed in the proportion of B cells (from 18.4 +/- 3.0% to 20.0 +/- 3.8%; P < 0.01) and T cells (from 64.2 +/- 4.1% to 67.1 +/- 4.2%; P < 0.01). A decrease in the proportion of NK cells was observed (from 13.4 +/- 2.7% to 9.8 +/- 2.2%; P < 0.01). The proportion of CD4+ cells increased (P < 0.01), and that of CD8+ cells decreased (P < 0.01), so that the CD4+ cell/CD8+ cell ratio increased (P < 0.01). The proportion of CD29+ (helper-inducer T) cells increased (P < 0.05), but that of CD45RA+ (suppressor-inducer T) cells did not change. NK cell activity decreased significantly (from 33.6 +/- 8.3% to 29.1 +/- 7.6%; P < 0.01).
Conclusions: A small but significant alteration in lymphocyte subsets and in NK cell activity by SGB indicates that local sympathetic nerve block may modulate the immune response.