Inhyung Lee

Distribution of new methylene blue injected into the dorsolumbar epidural space in cows

Objective To describe the effect of injection volume and anatomy on the spread of new methylene blue (NMB) injected into the epidural space between the first and second lumbar vertebrae in cows. Study Design Prospective experimental study. Sample Population Thirteen nonpregnant cows. Methods Cows were randomly assigned to two groups. Group 1 received 5 mL and Group 2 received 10 mL of 0.12% NMB in 0.9% saline. The injection was made into the first interlumbar epidural space using a dorsal approach. The extent of cranial and caudal migration of the dye, as manifested by the staining of the epidural fat and dura mater, was measured. Results Mean ± SEM number (range) of stained vertebrae was significantly greater in the 10-mL group than in the 5-mL group, 4.4 ± 0.6 (T11 to L5) and 3.0 ± 0.2 (T12 to L3), respectively (p < 0.05). Linear regression analysis showed that the volume was significantly correlated with the number of stained vertebrae (R2 = 0.42, p = 0.016). In the dorsal and lateral aspect of the spinal cord, there were two types of distribution of NMB along the surface of the epidural fat: between the periosteum and epidural fat; and between the epidural fat and dura mater. Migration under the spinal cord occurred along the two longitudinal epidural veins. Conclusions and Clinical Relevance The larger the volume of solution injected into the first interlumbar epidural space, the greater the spread. Intrinsic anatomic factors, such as characteristics of epidural fat and veins, influence the epidural spread of injected solution and, consequently, epidural analgesia.

Comparison of xylazine, lidocaine and the two drugs combined for modified dorsolumbar epidural anaesthesia in cattle

Twenty-four Holstein cattle scheduled for flank surgery in a standing position were randomly assigned to four groups of six. A 16 G, 120 mm Tuohy needle was inserted into the first interlumbar epidural space and its position was confirmed by the hanging drop technique. After air had been allowed to enter freely for approximately one minute, the epidural needle was slowly inserted 7 to 10 mm deeper to penetrate the epidural fat, and anaesthetic solution containing either 0˙05 mg/kg bodyweight xylazine hydrochloride (xylazine), 0˙025 mg/kg xylazine, 0˙025 mg/kg xylazine and 0˙1 mg/kg lidocaine hydrochloride (lidocaine), or 0˙2 mg/kg lidocaine alone was administered. Signs of sedation were observed in the three groups treated with xylazine and the number of spinal segments involved in the area of analgesia when the anaesthetic contained xylazine was significantly greater than with 0˙2 mg/kg lidocaine alone (P<0˙01). After the treatment with 0˙025 mg/kg xylazine and 0˙1 mg/kg lidocaine, flank surgery was performed successfully without additional line block or side effects.

Antagonistic effects of intravenous or epidural atipamezole on xylazine-induced dorsolumbar epidural analgesia in cattle.

This study was performed to clarify the antagonistic actions of intravenous or epidural atipamezole on the sedative and analgesic effects of xylazine administered between the epidural fat and dura mater through the first interlumbar space in cattle. Cattle received 5 mL of a solution containing 0.05 mg x kg(-1) xylazine in 0.9% saline. Thirty minutes later, 5 mL of 0.9% saline was administered through the same needle (treatment 1) (XSE). In treatments 2 (XAE) and 3 (XAV), 5 mL of a solution containing 0.025 mg x kg(-1) atipamezole in 0.9% saline was administered epidurally or intravenously, respectively. Sedation and analgesia were similar in all three treatment groups and could be reversed by atipamezole given by either route. In the XAV treatment, the flank area relapsed into analgesia 25+/-5.8 min following reversal of the analgesic effect, and was maintained for 112.5+/-63.8 min. The present study confirmed that the sedative and analgesic effects of xylazine are completely reversed by atipamezole and can be influenced by the epidural fat in cattle. Furthermore, it seems probable that analgesia following epidural administration of xylazine is mediated by alpha(2)-adrenergic receptors, not by a local anaesthetic effect.

Practical tips for modified dorsolumbar epidural anesthesia in cattle

Segmental dorsolumbar epidural anesthesia has been considered difficult to perform. The purpose of this study was to determine whether or not it is difficult for beginners to learn how to do modified dorsolumbar epidural anesthesia of cattle. Thirty cattle were divided into two groups, young (n = 8) and adult (n = 22), according to their age and body weight, and 0.12% new methylene blue (NMB) was injected into the first interlumbar (L1-L2) epidural space by four fifth-year veterinary school students who had never performed this method. After a 1 hour lecture on the modified dorsolumbar epidural anesthesia procedure which included basic anatomy and skills, each student successfully performed the procedure. In the young group, the NMB solution was distributed between the periosteum and the epidural fat (BPF) in one half and between the epidural fat and the dura mater (BFD) in the other half of the cattle. In about 60% (13/22) of the adult group, the NMB solution distributed as BFD type. This study showed that the modified dorsolumbar epidural anesthesia procedure is easy for beginners to perform if they overcome their fear about the deeper insertion of the epidural needle with basic anatomical knowledge and a little experience.