Effect of 3% chloroprocaine hydrochloride when used for median and ulnar regional nerve blocks in lame horses

Effect of video angle on detection of induced front limb lameness in horses

BACKGROUND

Lameness examinations are commonly performed in equine medicine. Advancements in digital technology have increased the use of video recordings for lameness assessment, however, standardization of ideal video angle is not available yielding videos of poor diagnostic quality. The objective of this study was to evaluate the effect of video angle on the subjective assessment of front limb lameness. A randomized, blinded, crossover study was performed. Six horses with and without mechanically induced forelimb solar pain were recorded using 9 video angles including horses trotting directly away and towards the video camera, horses trotting away and towards a video camera placed to the left and right side of midline, and horses trotting in a circle with the video camera placed on the inside and outside of the circle. Videos were randomized and assessed by three expert equine veterinarians using a 0-5 point scoring system. Objective lameness parameters were collected using a body-mounted inertial sensor system (Lameness Locator®, Equinosis LLC). Interobserver agreement for subjective lameness scores and ease of grading scores were determined.

RESULTS

Induction of lameness was successful in all horses. There was excellent agreement between objective lameness parameters and subjective lameness scores (AUC of the ROC = 0.87). For horses in the "lame" trials, interobserver agreement was moderate for video angle 2 when degree of lameness was considered and perfect for video angle 2 and 9 when lameness was considered as a binary outcome. All other angles had no to fair agreement. For horses in the "sound" trials, interobserver agreement was perfect for video angle 5. All other video angles had slight to moderate agreement.

CONCLUSIONS

When video assessment of forelimb lameness is required, a video of the horse trotting directly towards the video camera at a minimum is recommended. Other video angles may provide supportive information regarding lameness characteristics.

Dexmedetomidine prolongs the duration of action of mepivacaine on anesthesia of the palmar digital nerves of horses

OBJECTIVE

To determine whether palmar digital nerve (PDN) blockade in horses with a combination of dexmedetomidine and mepivacaine would block the response to mechanical force applied to the digit longer than would anesthetizing these nerves with mepivacaine alone or dexmedetomidine alone.

ANIMALS

8 mares with no signs of lameness.

PROCEDURES

In a randomized, crossover, blinded, experimental study, both PDNs of the same forelimb of each horse were anesthetized by perineural injection with either 30 mg mepivacaine alone, 250 µg of dexmedetomidine alone, or 30 mg mepivacaine combined with 250 µg of dexmedetomidine. Each horse received each treatment, and treatments were administered ≥ 2 weeks apart. The mechanical nociceptive threshold was measured at a region between the heel bulbs with the use of a digital force gauge before (baseline) and at 15-minute intervals after treatment.

RESULTS

The mean duration of sensory blockade of the digit was 2-fold longer when a combination of mepivacaine and dexmedetomidine was administered (371 minutes), compared with when mepivacaine alone was administered (186 minutes). Treatment with dexmedetomidine alone did not change the mechanical nociceptive threshold substantially from baseline and resulted in no clinical signs of sedation.

CLINICAL RELEVANCE

Results indicated that relief from digital pain provided by perineural treatment with mepivacaine for PDN blockade can be extended by adding dexmedetomidine to the injectate.

Comparison of 2% mepivacaine and a solution of 2% lidocaine/epinephrine administered for median and ulnar nerve blocks in horses with naturally occurring forelimb lameness

OBJECTIVE

To compare a 2% lidocaine solution containing 5 μg/ml (1:200 000) epinephrine with 2% mepivacaine for reducing lameness in horses after use in proximal nerve blocks.

STUDY DESIGN

Experimental randomized crossover.

ANIMALS

Six adult horses with naturally occurring forelimb lameness.

METHODS

Horses were evaluated using an inertial gait sensor system. Lameness was measured as a vector sum (VS). Following baseline lameness examination, median and ulnar nerve blocks were performed with lidocaine/epinephrine (0.5 mg epinephrine added to 50 ml of 2% lidocaine immediately prior to administration) or an equal volume of 2% mepivacaine. Horses were trotted at 5 min and then at 30 min intervals for 150 min. After 24 h, nerve blocks were repeated using the other local anesthetic. Data were evaluated using linear models.

RESULTS

The reduction in the VS did not differ after nerve blocks with lidocaine/epinephrine or mepivacaine (P = .791). Mean time to VS <8.5 mm (n = 5) was 5 and 9.6 min for lidocaine/epinephrine and mepivacaine, respectively. For one horse, VS was not reduced to <8.5 mm with either treatment (this horse had the highest VS before treatments were administered). The decrease in VS to <8.5 mm lasted for 150 min in both treatment groups.

CONCLUSION

The outcomes of the median and ulnar nerve blocks performed with 2% lidocaine with epinephrine did not differ from blocks performed with 2% mepivacaine.

CLINICAL RELEVANCE

Two percent lidocaine with epinephrine may serve as an adequate replacement for proximal nerve blocks when mepivacaine is unavailable.