Effects of dexmedetomidine on perioperative tip perfusion index and heart rate variability in patients undergoing thoracic surgery

Objective To investigate the effects of dexmedetomidine on perioperative tip perfusion index (TPI) and heart rate variability (HRV) in patients undergoing thoracic surgery.Methods Thirty ASA physical status Ⅰ or Ⅱ patients,aged 40-70 yr,weighing 38-80 kg,scheduled for elective radical operations for lung cancer,were randomly divided into 2 groups (n =15 each):control group (group C) and dexmedetomidine group (group D).Normal saline 20 ml was injected intravenously in group C,while dexmedetodine 1 μg/kg (20 ml) was injected intravenously in group D.Anesthesia was induced with target-controlled infusion (TCI) of propofol with the target plasma concentration (Cp) of 4 μg/ml,and iv injection of fentanyl 5 μg/kg (in group C) or 3 μg/kg (in group D) and rocuronium 0.9 mg/kg.When BIS value decreased to 50,a double lumen endobronchial tube was inserted.The patients were mechanically ventilated and PETCO2 was maintained at 35-45 mm Hg.Anesthesia was maintained with TCI of propofol with the Cp of 4 μg/ml,infusion of dexmedetodine 0.5 μg· kg-1 · h-1,and injection of fentanyl 0.1 mg when needed in group D,or with TCI of propofol with the Cp of 4μg/ml and intermittent iv boluses of fentanyl 0.1 mg in group C.Before induction (T0),immediately before and after intubation (T1,2),immediately after skin incision (T3),immediately after splitting of sternum (T4),at 30 min and 1 h after chest opening (T5,6),and at the end of operation (T7),TPI,low frequency power (LF) and high frequency power (HF)were recorded,and LF/HF ratio was calculated.The development of cardiovascular events was recorded.Results Compared with group C,TPI at T3-7 was significantly increased,LF/HF ratio at T4-6 was decreased,and the incidence of hypertension was decreased in group D (P ＜ 0.05).Conclusion Dexmedetomidine can improve microcirculation through decreasing sympathetic activity in patients undergoing thoracic surgery. Key words: Dexmedetomidine;  Plethysmography ;  Heart rate