Quantitation of the anaesthetic xylazine in ovine plasma by LC-MS/MS.

Removal of the wool-bearing skin around a young lamb's rump (mulesing) provides long term health benefits for the animal, and the use of a sedative and analgesic agent such as xylazine may assist with pain relief to reduce discomfort and stress. Sensitive analytical methods are essential for monitoring pharmaceuticals and their metabolites in animals destined for human consumption. The following work reports a method that is 200 times more sensitive for xylazine detection than previously published methods, with lower limits of quantitation for xylazine and its primary metabolite in animals of 0.5pg and 2pg on-column, respectively. The use of a square wave solvent gradient immediately prior to analyte elution resulted in larger MS/MS peaks and a reduction in baseline noise, allowing reliable detection of lower analyte concentrations. The method uses as little as 1mL of plasma which allows replication within a sample if required, and requires simple sample preparation, minimising the introduction of matrix components into the MS/MS.

Distensible superficial venous orbital malformations involving the lower eyelid in two horses.

CASE DESCRIPTION: 2 horses were examined because of vascular masses involving the lower eyelid. CLINICAL FINDINGS: Both horses had a unilateral, fluctuant mass involving the lower eyelid. For horse 1, the mass had been present since birth and had slowly increased in size over time. The mass also changed in size in response to various environmental stimuli, alterations in the position of the horse's head, and digital obstruction of superficial vessels adjacent to the mass. Horse 2 was brought to the hospital for euthanasia, and no historical or antemor-tem data were available. A combination of contrast angiography, Doppler ultrasonography, surgical exploration, and blood gas analysis (horse 1) and postmortem and histologic examination (horse 2) were used to determine that the masses consisted of non-neoplastic distended venous channels with anastomoses to the inferior lateral palpebral and angularis oculi veins (both horses) as well as the facial vein (horse 2). Histologic examination (horse 2) revealed large, endothelial cell-lined, blood-filled spaces within the deep dermis consistent with a distensible superficial venous orbital malformation. TREATMENT AND OUTCOME: Horse 1 underwent surgical exploration and ligation of the vascular malformation. Six months after surgery, the mass was markedly reduced in size, and size of the mass was static regardless of head position or environmental stimuli. CLINICAL RELEVANCE: Thorough preoperative planning with Doppler ultrasonography, contrast angiography, and blood gas analysis is recommended when attempting surgical correction of these malformations in horses. Surgical ligation can result in a successful cosmetic and functional outcome.