Effects of thoracic and lumbar epidural block on depth of propofol sedation

Objective To evaluate the effects of thoracic and lumbar epidural block on the depth of propofol sedation.Methods Forty-five ASA Ⅰ or Ⅱ patients with stomach cancer ( n =15) or colorectal cancer ( n =30) aged 20-64 yr weighing 46-79 kg with body height 151-179 cm undergoing elective radical operation were enrolled in this study.The 30 patients with colorectal cancer were randomly divided into 2 groups ( n =15 each):group control (group Ⅰ ) and group lumbar epidural group(group Ⅱ ).The 15 patients with stomach cancer received thoracic epidural block (group Ⅲ ).Epidural block was performed at L2.3 interspace in groups Ⅰ and Ⅱ and at T9.10 interspace in group Ⅲ.After a test dose of 3 ml 1.5％ lidocaine,a bolus of 1.5％ lidocaine 12 ml (in groups Ⅱ and Ⅲ ) or 12 ml of normal saline (in group Ⅰ ) was injected into epidural space.Target-controlled infusion(TCI) of propofol was started at 12 min after epidural lidocaine.Target plasma concentration of propofol was set at 4 μg/ml.Fentanyl 4 μg/kg was injected iv as soon as the patients lost consciousness.Tracheal intubation was facilitated with vecuronium 0.1 ng/kg.The patients were mechanically ventilated.Radial artery was cannulated for direct BP monitoring and blood sampling.BIS value was monitored (Aspect Medical System).The number of spinal sequent affected in the subarachnoid epidural anesthesia was counted before propofol TCI.Arterial blood sampies were collected at 2,3,4 and 5 min of propofol TCI for determination of plasma concentration of propofol ( by HPLC).BIS value and plasma concentration of propofol calculated by TCI pump were recorded at 2,3,4 and 5 min of propofol TCI.Results The BIS values were significantly lower in groups Ⅱ and Ⅲ than in group Ⅰ and in group Ⅲ than in group Ⅱ.There was no significant difference in plasma propofol concentration measured by HPLC and plasma concentration of propofol calculated by TCI pump.Conclusion The efficacy of thoracic epidural block enhancing propofol sedation is higher than that of lumbar epidural block. Key words: Anesthesia, epidural;  Propofol;  Conscious sedation