POSTOPERATIVE ANALGESIA AFTER PERIPHERAL-NERVE BLOCK FOR PODIATRIC-SURGERY - CLINICAL EFFICACY AND CHEMICAL-STABILITY OF LIDOCAINE ALONE VERSUS LIDOCAINE PLUS CLONIDINE

Postoperative analgesia may be prolonged by the addition of clonidine to local anesthetic solutions used for regional anesthesia. The purpos e of this study was to test this hypothesis in a clinical trial of pat ients undergoing pediatric surgery. The study design was prospective, double-blinded, and randomized. Ninety ASA physical status I or II pat ients scheduled for bunionectomy or hammer toe repair were randomized to receive ankle or metatarsal blocks with plain 1.73% lidocaine (Grou p L), 1.73% lidocaine with 10 mu g/mL, of clonidine added (Group C-10) , or 1.73% lidocaine with 20 mu g/mL clonidine (Group C-20). 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 postoperativ e oral pain medication required in the first 9 h after the block was a lso recorded. Analysis of variance (ANOVA) was used to analyze intergr oup differences in the VAS and verbal pain scores, the time to first r eported pain, the time to first oral pain medication, and the total am ount of oral pain medications required. Repeated-measures ANOVA was us ed to analyze the VAS and verbal pain scores overall and integrated as sessment of pain scores and rescue medication was per-formed. Adverse events were also recorded for each group. There were no differences am ong the three groups with regard to overall VAS pain scores although G roup C-10 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 C-10 had a longer time to first reported pain (P < 0.01), a longer time to first oral pain meditation (P < 0.0 1), 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 C-10 reported no pain postope ratively (P < 0.01) and no pain medication taken (P < 0.01) than Group L. Group C-20 results suggested no statistically significant improvem ent over plain lidocaine. One patient in Group C-20 experienced signif icant hypotension postoperatively. pH determinations and chemical anal ysis by capillary electrophoresis showed no significant change in comp osition of the solutions when clonidine was mixed with lidocaine and s tored at 4 degrees C for 1 wk. Compared to 1.73% lidocaine, combining clonidine (10 mu g/mL) with lidocaine for local anesthetic block for f oot surgery significantly increases the duration and quality of postop erative analgesia.