Effects of Alkalinization of Local Anesthetics on Anesthetic Action in Epidural Anesthesia for Cesarean Section

Kim, Keon Soo; Paek, Seung Hee; Roh, Woon Seok; Cho, Soung Kyung; Lee, Sang Hwa

Abstract

Several studies have indicated that the addition of sodium bicarbonate and opioid to soiutions of locl anesthetics shortens the onset time,increases the intensity and prolongs the duration of neural blockade. This study was performed to compare onset times and duration of neural blockade in each groups. Eighty-two parturients scheduled for cesarean section at term under epidural anesthesia were assigned to three groups. Group 1 (n=19) received 1.5% lidocaine hydrochloride (pH 6.32+/-0.01), group 2 (n=26) received 1.5% lidocaine hydrochloride plus fentanyl 50 mcg (pH 6.27+/-0.02) and group 3 (n=37) received l.5% lidocaine hydrochloride plus fentanyl 50 mcg plus 8.4% sodium bicarbonate (sodium bicarbonate l mEq/lidocaine 10 ml)(pH 7.32+/-0.03). All groups were given 22-28 ml of local anesthetic solutions according to their height. Onsei times and duration of sensory blockade were evaluated using pin prick test at two minutes interval after epidural injection at L2, 76, T4 dermatomes. Onset timcs (time between the completion of anesthetic injection and loss of pin prick sensation at each dermatome) of sensory blockade at L2 dermatome were 3.1+/-0.2 minutes in Group 3, which were shorter than 5.0+/-0.3 minutes in Group l and 4.7+/-0.4 minutes in Group 2 (p<0.05). At T6 dermatome, onset times of sensory blockade were 6.9+/-0.6 minutes in Group 3, which were shorter than 15.4+/-1.2 minutes in Group l and 12.9+/-1.0 in Group 2 (p<0.05). At T4 dermatome, onset times of sensory blockade were 10.l+/-0.2 minutes in Group 3, which were shorter than 22.3+/-1.2 minutes in Group 1 and 18.8+/-1.1 in Group 2 (p<0.05). The duration (time between loss of pin prick sensation and complete recovery of pain at each dermatome) of sensory blockade at T4 dermatome in Group 3 were 74.0+/-3.8 min, which were longer than 52.9+/-2.4 minutes in Group 1 and 52.7+/-1.4 minutes in Group 2 (p<0.05). The duration of sensory blockade at L2 dermatome in Group 3 were 119.6+/-4.4 minutes,which were longer than 78.6+/-4.8 minutes in Group 1 and 81.6+/-2.5 minutes in Group 2 (p<0.05). The above results suggested that alkalinization of lidocaine solution is an effective way to shorten the latency and to prolong the duration of epidural block for cesarean section.