"comparative study of onset and duration of action of 0.5% bupivacaine and a mixture of 0.5% bupivacaine and 2% lidocaine for epidural anesthesia"

local anesthetic solutions are frequently mixed to take advantage of the useful properties of each drug but the medical literature is surprisingly deficient in well controlled studies about the onset and duration of action of these mixtures for epidural anesthesia. a total of 32 patients scheduled for elective operation were enrolled in this prospective randomized controlled study; in group i, 16 patients received 15 ml solution containing bupivacaine 0.5% and lidocaine 2% as a single injection epidural anesthesia after 3 ml test dose containing 15 mcg epinephrine; in group ii, 16 patients received 15 ml bupivacaine 0.5% with the same technique. the times from injection of the test dose to the onset of sensory anesthesia at inguinal ligament and umbilicus and the time of termination of anesthesia at the maximum sensory level and two levels regression of anesthesia level were checked with pinprick test. the results were compared with two sample t test. times to onset of sensory block in l1 and t10 levels (mean±sd) were 14.87±3.1 min and 21±3.37 min in group i and 17.12±2.18 min and 24.9±2.54 min in group ii, respectively (p< 0.025 and p< 0.001, respectively). times to termination of sensory anesthesia at the maximum level of anesthesia and two dermatomes regression were 75.12±8.26 min and 87.8±7.01 min in group i and 116.37±22.4 min and 134.87±21.64 min in group ii, respectively ( p= 0 and p=0,respectively). mixing lidocaine 2% with bupivacaine 0.5% in a 1:1 ratio compared to 0.5% bupivacaine solution results in significantly more rapid initiation and termination of sensory block.