Clinical Evaluation of Alkalinized Lidocaine for Epidural Anesthesia / 대한마취과학회지

ABSTRACT

Epidural anesthesia is often preferred over spinal anesthesia because of it's more gradual onset of action and less precipitous hypotension. But, there may be a delay in onset and incomplete blockade at I 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 charged 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; 200,000 epinephrine plus l mEq of NaHCO added per 10 ml of lidocaine solution. The onset of sensory blockade was measured by pin prick test, and onset time of analgesia was defined as the time between 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. Results were as follows; 1) Time to onset of anaIgesia at L1, T10, T5 S1 dermatome were significantly more rapid in group that received the alkalinized Iidocaine 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 bloekade, quality of neural blockade was improved and onset of anesthesia and development of systolic hypotension were more rapid.