Abstract
Xylazine (0.0025 ml/kg of 2% xylazine and 4 ml of 0.9% NaCl), xylazine/lidocaine (0.0025 ml/kg of 2% xylazine and 4 ml of 2% lidocaine), or saline (0.0025 ml/kg plus 4 ml of 0.9% NaCl) was given epidurally through indwelling catheters placed 20 cm cranial from the thoracolumbar intervertebral space in 4 adult cows. Each cow received all the regimens at weekly interval in a Latin Square design. Immediately after epidural injection, the cows were cast with ropes, positioned in dorsal recumbency and restrained in this position for 60 min. Analgesia was defined as a lack of response to deep pinprick on the left and right body walls and on the middle body wall of 20×20 cm width between the xiphoid and the umbilicus (the middle area), corresponding to the incision site of the paramedian approach for abomasopexy. Though xylazine and xylazine/ lidocaine produced analgesia of the lateral body walls (max dermatomes of T7 to L3) and of the middle area 5 to 30 min after epidural injection, 2 cows given xylazine and 1 cow given xylazine/lidocaine produced imcomplete analgesia at the cranial portion of the middle area. Struggling against dorsally recumbent restraint occurred in cows of all the groups. Mean arterial blood pressure did not change in saline-injected cows, but decreased by about 20% in xylazine-and xylazine/lidocaine-injected cows at 20 and 30 min after epidural injection. Significant decrease in PaO2 developed in cows of all the groups at 10 to 60 min after epidural injection but returned to normal level in 10 min after standing.
