Comparison of lidocaine, xylazine, and lidocaine-xylazine for caudal epidural analgesia in cattle.

OBJECTIVE To directly compare the time to onset and duration of analgesia produced by a lidocaine/xylazine combination with that produced by lidocaine and xylazine administered alone in the caudal epidural space of dairy cattle. Design   Prospective randomized experimental study. ANIMALS Nine adult (> 4 years of age) dairy cows (520-613 kg). METHODS Caudal epidural analgesia was produced in all cows with 2% lidocaine (0.22 mg kg-1; 5.5 mL 500 kg-1), 10% xylazine (0.05 mg kg-1 diluted to 5.5 mL 500 kg-1 with sterile water), and 2% lidocaine/10% xylazine (0.22 mg kg-1/0.05 mg kg-1; total volume of 5.7 mL 500 kg-1), at no earlier than weekly intervals in a Latin square design. Time to onset, duration and cranial spread of analgesia were recorded, as were degree of sedation, ataxia and ptyalism. RESULTS No significant difference (p > 0.05) was noted for time (mean ± SEM) of onset of analgesia between lidocaine (4.8 ± 1.0 minutes) and the lidocaine/xylazine combination (5.1 ± 0.9 minutes) but onset of analgesia following xylazine was significantly longer (11.7 ± 1.0 minutes) than either of the other two treatments. Lidocaine/xylazine (302.8 ± 11.0 minutes) produced analgesia of significantly longer duration than that of xylazine (252.9 ± 18.9 minutes) and both the lidocaine/xylazine combination and xylazine alone produced analgesia of significantly longer duration than that produced by lidocaine (81.8 ± 11.8 minutes). In all cattle, xylazine, administered either alone or with lidocaine, induced mild to moderate sedation and ataxia and cutaneous analgesia from the coccyx to T13. Mild ataxia was also present in those cattle receiving lidocaine alone. CONCLUSION The combination of xylazine and lidocaine produces analgesia of quicker onset and longer duration than xylazine administered alone and of longer duration than lidocaine administered alone. CLINICAL RELEVANCE Utilizing this combination, long-duration obstetrical and surgical procedures could commence relatively soon after epidural injection and could be completed without re-administration of anesthetic agents.