Comparison of 2% lidocaine and hyperbaric 5% lidocaine for caudal epidural analgesia in horses

This study aimed at comparing lidocaine 2% plain with lidocaine 5% with glucose 7.5% for caudal epidural analgesia in horses. Eighteen clinically healthy mixed breed horses were studied. The animals were randomly divided into three treatments: lidocaine plain (LID) treatment received 0.20 mg/kg of body weight (mean dose 3.2 mL); heavy lidocaine (HLID) treatment received 0.5 mg/kg of body weight (mean dose 3.2 mL), and 0.9% saline solution (SS) 5 mL as a control treatment. All drugs were injected by the epidural route in all animals between the first and second coccygeal space. Heart rate, arterial pressure, respiratory rate, rectal temperature, analgesia, and motor-blocking were determined before drug administration (baseline values); at 5, 10, 15, and 30 minutes after drug administration, and then at 30-minute intervals thereafter. The onset of analgesia was 7.5 minutes ± 2.7 minutes after injection of hyperbaric lidocaine, opposed to 11.7 minutes ± 4 minutes after lidocaine plain. The duration of analgesia was 156 minutes ± 17.4 minutes for hyperbaric lidocaine and 115 minutes ± 16 minutes for lidocaine plain. Heart rate and arterial pressure did not change (P < .05) significantly from basal values after the epidural administration of hyperbaric lidocaine and lidocaine plain. Respiratory rate and rectal temperature decrease (P < .05) significantly from basal values in the lidocaine plain treatment. Saline solution did not change any parameters studied. We conclude that epidural hyperbaric lidocaine produces longer analgesia with less motor-blocking than lidocaine plain in horses. However, because lidocaine plain and hyperbaric lidocaine were not administered at equipotent dosages, the relative potential for both drugs to induce surgical analgesia in standing horse remains to be determined.