Effects of epidural analgesia using different concentrations of bupivacaine during combined general and epidural anesthesia

INTRODUCTION: Thoracic epidural analgesia, combined with general anesthesia, is an established anesthetic choice for abdominal aortic surgery. However, there are controversies about the level of anesthesia as well as the dose and concentration of the local anesthetic used. The aim of the study was to compare the effects of two different concentrations of epidural bupivacaine on sevoflurane requirements and hemodynamic parameters during aortic surgery under combined epidural/general anesthesia. METHODS AND MATERIAL: Sixty patients scheduled for abdominal aortic surgery were randomly divided into two groups according to the concentration of local anesthetic used for epidural anesthesia: group 1--low concentration--where 0.125% bupivacaine was used, and group 2--high concentration--where 0.5% bupivacaine was used at the beginning and then the concentration was reduced to 0.25%. Anesthesia was maintained with sevoflurane, the dose was adjusted to achieve the target entropy of 40-60. The measurements included the inspired sevoflurane concentrations, blood pressure, and heart rate at the beginning and every 5 min during the surgery. RESULTS: Both groups had similar heart rate and blood pressure, but the inspired sevoflurane concentration was significantly higher and more variable in patients where bupivacaine 0.125% was used. Vasopressors were used more often and in higher doses in the 0.5% bupivacaine group, and in the same group the blood loss and fluid requirements were reduced. CONCLUSION: When 0.5% bupivacaine is used in combined thoracic epidural/ general anesthesia for aortic surgery, the sevoflurane concentrations are lower and less variable. In addition, the blood loss and fluid requirements are reduced.