EFFECT OF XYLAZINE, DETOMIDINE, AND A COMBINATION OF XYLAZINE AND BUTORPHANOL ON EQUINE DUODENAL MOTILITY

Objective-To evaluate the effect on equine duodenal motility of some a nalgesic agents commonly used to treat colic. Animals-4 healthy adult healthy horses-2 mares and 2 geldings-which were carrying an indwellin g gastric cannula made of silastic rubber. One horse also carried 2 lo ng-term indwelling bipolar electrodes that had been sutured onto the d uodenum and jejunum. Procedure-To ensure an empty stomach, solid food was withheld from horses for around 20 hours prior to an experiment. U sing videoendoscopic guidance, an 8-F catheter with 3 small, discrete pressure sensors was passed through the gastric cannula and directed i nto the proximal portion of the duodenum. Deflection of the recording pen, to which the catheter was attached, indicated a motile event in t hat section. Drugs (treatment) were given into the jugular vein in a r andomized block design, 1 treatment/experiment, after a 1-hour baselin e recording. Treatments were: 2 mi of 0.9% NaCl, xylazine (XYL, 0.5 mg /kg of body weight), detomidine (DET, 0.0125 mg/kg), or a xylazine/but orphanol combination (XYB, 0.5/0.05 mg/kg). Each horse received each t reatment twice. All positive pressure peaks > 5 mm of Hg recorded from the most proximal sensor on the catheter were counted in 15-minute bl ocks. Each mean 15-minute posttreatment value was compared with the ba seline value for that specific treatment. Results-There was no signifi cant difference between baseline values. All treatments significantly (P < 0.05) reduced frequency of pressure peaks below their respective pretreatment values, but to variable degrees and durations. Comparativ ely, XYL had the least effect, with mild, though significant, reductio n for only the first 30 posttreatment minutes; DET and XYB caused a si gnificant marked reduction for 1 hour after treatment. Conclusions-The profound suppressive effect of a routine dose of detomidine or xylazi ne/butorphanol combination on equine duodenal motility must be conside red when using these agents for management of colic, especially when e ncouragement of intestinal motility is desirable.