Objective To invetstigate the effects of right stellate ganglion block (SGB) on heart rate variability (HRV) in patients with carbon dioxide pneumoperitoneum.Methods Forty ASA Ⅰ or Ⅱ patients of both sexes,aged 39-75 yr,weighing 47-75 kg,undergoing elective laparoscopic cholecystectomy,were randomly divided into 2 groups ( n =20 each):control group (group C) and right SGB group (group SGB).Right SGB was performed with 1％ lidocaine 7 ml at 10 min before induction of anesthesia.The low frequency power ( LF),high frequency power (HF),total power (TP) and LF/HF ratio were recorded before SGB (baseline,To ),at 5 and 30 min of pneumoperitoneum (T1,2),at 5 min after deflation (T3) and at the end of operation (T4 ).The LF in normalized units (LFnu) and HF in normalized units (HFnu) were calculated.Results Compared with the baseline values at T0,LF,LFnu and LF/HF ratio were significantly increased at T1-4,HF was significantly decreased at T3,4,and HFnu was significantly decreased at T2-4 in group C,and HF was significantly increased at T1-4,HFnu was significantly increased at T2-4 and LF/HF ratio was significantly decreased at T1-4 in group SGB ( P ＜ 0.05 or 0.01 ).LF,LFnu and LF/HF ratio were significantly decreased at T1-4,and HF at T1-4 and HFnu at T2-4 were significantly increased in group SGB as compared with group C ( P ＜ 0.05 or 0.01 ).Conclusion Right SGB can not only inhibit the sympathetic activity induced by carbon dioxide pneumoperitoneum,but also increase the vagal tone.