Postoperative
analgesia may be prolonged by the addition of
clonidine to
local anesthetic solutions used for
regional anesthesia. The purpose of this study was to test this hypothesis in a clinical trial of patients undergoing podiatric surgery. The study design was prospective, double-blinded, and randomized. Ninety ASA physical status I or II patients scheduled for bunionectomy or
hammer toe repair were randomized to receive ankle or metatarsal blocks with plain 1.73%
lidocaine (Group L), 1.73%
lidocaine with 10 micrograms/mL of
clonidine added (Group C10), or 1.73%
lidocaine with 20 micrograms/mL
clonidine (Group C20). Time from the performance of the block to 1) loss of sensation to pinprick, 2) return of sensation to pinprick, 3) onset of
postsurgical pain, and 4) time of first oral
pain medication intake were recorded. Beginning at 1 h after the completion of the block, visual analog scale (VAS) and verbal
pain scores were recorded every 30 min. Additional postoperative oral
pain medication required in the first 9 h after the block was also recorded. Analysis of variance (ANOVA) was used to analyze intergroup differences in the VAS and verbal
pain scores, the time to first reported
pain, the time to first oral
pain medication, and the total amount of oral
pain medications required. Repeated-measures ANOVA was used to analyze the VAS and verbal
pain scores overall and integrated assessment of
pain scores and rescue medication was per-formed. Adverse events were also recorded for each group. There were no differences among the three groups with regard to overall VAS
pain scores although Group C10 had significantly better verbal
pain scores after the first 3 h (P < 0.05). There was also no difference in time to loss or return of pinprick sensation. Group C10 had a longer time to first reported
pain (P < 0.01), a longer time to first oral
pain medication (P < 0.01), a lower average total dose of oral
pain medication required (P < 0.05), and a lower integrated assessment of
pain and medication (P < 0.01) than Group L. More patients in Group C10 reported no
pain postoperatively (P < 0.01) and no
pain medication taken (P < 0.01) than Group L. Group C20 results suggested no statistically significant improvement over plain
lidocaine. One patient in Group C20 experienced significant
hypotension postoperatively. pH determinations and chemical analysis by capillary electrophoresis showed no significant change in composition of the solutions when
clonidine was mixed with
lidocaine and stored at 4 degrees C for 1 wk. Compared to 1.73%
lidocaine, combining
clonidine (10 micrograms/mL) with
lidocaine for
local anesthetic block for foot surgery significantly increases the duration and quality of postoperative
analgesia.