Epidural anesthesia is often preferred over spinal anesthesia because of its more gradual onset of action and less precipitous hypotension. But , there may be a delay in onset and incomplete blockade at L5 and S1 segments due to the large size of
these
nerve roots.
Increasing the pH of local anesthetic solution toward the physiologic range has been reported to improve the quality of neural blockade in vitro. Local anesthetic solution applied to a nerve membrane exits in two forms; nonionized free base and
charge
ionized cation. An increase in the nonionized fraction of local anesthetics associated with an increase in pH results in improved nerve penetration and more rapid onset time of nerve blockade.
This study was undertaken to determine the effect of increase in the pH of the lidocaine solutions used for epidural administration on time of onset of sensory blockade and quality of motor blockade, One hundred ten patients having epidural
anesthesia
for lower extremity orthopedic procedures, perineal and lower abdominal procedures were randomly assigned to two groups and the following local anesthetic solutions were epidurally injected. Group 1 received 2% lidocaine solution with 1;200,000
epinephrine and group 2 received 2%lidocaine solution with 1;200,000epinephrine plus 1 mEq of NaHCO3 added per 10ml of lidocaine solution.
The onset of sensory blockade was measured by pin prick test, and onset time of analgesia was defined as the time beteen the completion of anesthetic injection and loss of pinprick sensation. Motor blockade was assessed by modified Bromage scale
every 5
minutes for 30 min. Blood pressure and pulse rate were measured before epidural injection and every 5 min after injection for 30 min.
@ES Results were as follows;
@EN 1) Time to onset of analgesia at L2, T10, T6, S1 dermatome were significantly more rapid ingroup that received the alkalinazed lidocaine solution.
2) Degree of motor blockade were significantly more intense in alkalinized lidocaine group from 5 min to 25 min.
3) The decrease in systolic pressure in alkalinized group were more rapid than control group.
In conclusion, when lidocaine plus epinephrine alkalinized with bicarbonate was used during epidural blockade, quality of neural blockade was improved and onset of anesthesia and development of systolic hypotension were more rapid.
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