Evaluation of Low-Level Laser Effects on Epidural Anesthesia in Horse

Objective- To evaluate and compare the analgesic effects of caudal epidural administration of lidocaine (LIDO), caudal laser radiation and epidural lidocaine plus laser radiation in horses. Study design- A blinded, randomized, prospective, experimental cross-over study. Animals- Five healthy horses, 15.7 +/- 4.9 years of age, weighing 240 +/- 37 kg. Methods- The horses were randomly assigned to receive four treatments (group NS: saline (0.9% NaCl) solution via caudal epidural injection, group L: lidocaine (2 mg/kg of body weight) via caudal epidural injection, group LLL: laser radiation (3000Hrtz- for 10 minute) and group LL: caudal epidural lidocaine injection plus laser radiation at intervals of at least 1 week. A 20 gauge 55*0.9 mm needle was placed in the first intercoccygeal space (Co1-Co2) in conscious standing horses restrained in stocks for epidural injections. Two metal sheets were sticked in pocket like bags on position of origin and insertion of semitendinosus muscle in right and left sides for electrical stimulation response and motor and sensory blockade evaluations used by TENS machine. Degree of perineal analgesia was also assessed by pin prick induced with a 20 gauge 55*0.9 mm needle and pinch test evaluated by use of a hemostat clamp. Anal and vaginal tone was also recorded. Positive pain responses were defined as purposeful avoidance movements of the head toward the stimulation site were used to indicate analgesia. Results- All epidural injections were made without problems. Analgesia produced in the tail, perineum and upper hind limb in all horses received lidocaine. Statistical analyses assessing sensory and motor stimulation did not show a significant difference between horses in groups 1, 2, 3, 4 in right and left sides. Conclusion and clinical Relevance- We concluded that low level laser in combination with caudal epidural lidocaine treatments provided sufficient analgesia in horses, and this treatment is offered a longer duration of analgesia than laser, lidocaine caudal administration although the sensory and motor stimulation did not show significant difference between groups. Low level laser may be effective adjuvants in caudal epidural anesthesia in horses. Our results showed that LLL plus lidocaine may be preferable to a high dose of epidural lidocaine.