Cardiorespiratory effects of a tiletamine/zolazepam-ketamine-detomidine combination in horses

Objective-To determine cardiorespiratory effects of a tiletamine/zolazepam- ketamine-detomidine (TZKD) combination in horses. Animals-8 healthy adult horses. Procedure-Horses were instrumented far measurement of cardiorespiratory, ac id-base, and electrolyte values. Each horse was given xylazine (0.44 mg/kg of body weight, IV) 10 to 15 minutes prior to induction of recumbency by ad ministration of the TZKD combination. Cardiorespiratory, acid-base, and ele ctrolyte values were measured at 5-minute intervals for greater than or equ al to 30 minutes. Results-All horses became recumbent within 1 minute after IV administration of TZKD. Mean +/- SD duration of recumbency was 40 +/- 8 minutes. All hors es regained standing position after less than or equal to 2 attempts. Quali ty of anesthesia and analgesia was determined to be satisfactory in all hor ses. Xylazine induced decreases in respiratory rate, heart rate, cardiac ou tput, maximum rate of increase of right ventricular pressure, and rate pres sure product. The PaCO2 right atrial pressure, and peripheral vascular resi stance increased, whereas blood temperature, PO2, pHa, HCO3- PCV, total sol ids, Na, and K values remained unchanged. Subsequent administration of TZKD caused right atrial pressure and PaCO2 to increase and PaO2 to decrease, c ompared with values obtained after xylazine administration. Remaining cardi orespiratory, acid-base, hematologic, and electrolyte values did not differ from those obtained after xylazine administration. Conclusion-IV administration of TZKD induces short-term anesthesia in horse s. Potential advantages of this drug combination are the small volume of dr ug administered; minimal cardiorespiratory depression; quality of induction and maintenance of, and recovery from, anesthesia; and duration of drug ef fects.