Background: Regional blocks prevent impulses from the peripheral nociceptive receptors reaching the thalamus and the reticular activating system. This in turn reduces the load on the cortex thereby decreasing EEG activity. The entropy which measures the chaos of EEG activity is suppressed by increasing the concentration of inhaled anaesthetic as well and is used as a measure of depth of anaesthesia. In this double blinded study, we have attempted to quantify the influence of adding epidural blockade on the requirement of the general anaesthetic required to achieve a predetermined depth of anaesthesia guided by entropy monitoring during abdominal surgeries.

Methodology: Forty patients posted for elective laparotomies were randomized to two groups. All patients received a bolus followed by an infusion epidurally. Group GE received epidural bupivacaine 0.25% and Group GS, epidural saline. Both groups received narcotic, relaxant, Sevoflurane anaesthesia guided by entropy monitoring. End tidal Sevoflurane concentration (Etsevo) was titrated using up down method to find the lowest Etsevo to maintain entropy between 40 and 60 throughout the surgery in both groups.

Results: There was a significant reduction in the Etsevo required to maintain entropy between 40 and 60 in the epidural bupivacaine group (0.53%) compared to the control group (0.95%) (p = 0.000).

Conclusion: Deafferentation with Epidural analgesia reduced Sevoflurane requirements by 44.2%. Lower concentrations of volatile anaesthetic are required whenentropy guided general anaesthesia is combined with regional blockade.