Effect of intratesticular injection of xylazine/ketamine combination on canine castration.

This study was performed to compare the effect of intratesticular (IT) injection of xylazine/ketamine combination for canine castration with those of intramuscular (IM) or intravenous (IV) injection. Xylazine and ketamine was administered simultaneously via intratesticularly (IT group), intramuscularly (IM group) or intravenously (IV group) at doses of 2 and 10 mg/kg, respectively. Pain response at the time of injection, mean induction time, mean arousal time, mean walking time and cardiopulmonary function during anesthesia were monitored after the xylazine and ketamine administration. In IV and IM groups, heart rates were significantly decreased 30 and 45 min after xylazine and ketamine administration, respectively (p < 0.05). Respiratory rates were significantly decreased in the IV group (p < 0.05). In the IT group, there was no significant changes in heart and respiratory rates. The occurrence of cardiac arrhythmias was less severe in IT group compared with those in IM and IV groups. The route of administration did not affect rectal temperature. Mean induction time was significantly (p < 0.05) longer in IT group than in IM and IV groups. On the contrary, mean arousal time and mean walking time were shortened in IT group. Clinical signs related to pain response at the time of injection and vomiting were less observed in IT group than in IM group, and head shaking was less shown in IT group than in IM and IV groups during recovery period. These results indicated that intratesticular injection of xylazine/ketamine for castration has several advantages such as less inhibition of cardiopulmonary function and fast recovery from anesthesia without severe complications, and would be an effective anesthetic method for castration in small animal practice.

Use of yohimbine to reverse prolonged effects of xylazine hydrochloride in a horse being treated with chloramphenicol.

A 1-year-old Standardbred gelding had received xylazine hydrochloride (0.75 to 1.00 mg/kg [0.34 to 0.45 mg/lb] of body weight, IV) during 2 surgeries for debridement of a wound. The horse was given chloramphenicol (55 mg/kg [25 mg/lb], PO, q 6 h) for 5 days, and was anesthetized a third time with xylazine (0.75 mg/kg, IM). Five hours after administration of xylazine, the horse remained markedly sedated and had clinical signs of gaseous distention of the large bowel (bloat) requiring trocharization. Administration of yohimbine (0.03 mg/kg [0.01 mg/lb], i.v.) eliminated signs of sedation within 5 minutes. Moderate flatulence developed, and gastrointestinal sounds could be heard within all 4 abdominal quadrants within 15 minutes of yohimbine administration. The remainder of recovery was unremarkable. Xylazine induces bradycardia and decreases gastrointestinal motility in addition to causing sedation, muscle relaxation, and analgesia. Chloramphenicol can inhibit oxidase activity of cytochrome P-450 and inhibit metabolism and elimination of drugs such as xylazine.

Comparison of the postoperative analgesic and sedative effects of carprofen and papaveretum in the dog.

Forty dogs undergoing a variety of surgical procedures were assigned randomly to one of two groups. All the animals were premedicated with acepromazine (0.05 mg/kg bodyweight) intramuscularly, and anaesthesia was induced with thiopentone sodium, or propofol in the case of lean animals, and maintained with halothane in an oxygen/nitrous oxide mixture using a non-rebreathing circuit. The dogs in group 1 were given papaveretum (0.2 mg/kg) slowly intravenously within 35 minutes of induction of anaesthesia and the dogs in group 2 were given carprofen (4 mg/kg) in the same way. The dogs were scored for sedation and pain by a trained theatre nurse, who did not know which group they belonged to, using a visual analogue scale, at 15, 30, 60, 120, 240 and 360 minutes after the halothane was switched off at the end of the procedure. Nine of the dogs were withdrawn from the trial (eight of them from the papaveretum group) because of inadequate pain relief and these animals were given pethidine (3 mg/kg intramuscularly) which produced adequate analgesia within 15 minutes in all but one case. Carprofen provided profound analgesia which was as effective and of longer duration than that produced by papaveretum, and was associated with significantly less postoperative sedation and a quicker return to the normal conscious state.

Surgical treatment of uterine torsion in a llama (Lama glama).

A multiparous llama was presented because of failure to proceed into the second stage of labor. Clockwise uterine torsion and a live fetus were identified by rectal and vaginal examinations. A cesarean operation was elected because of the prolonged first stage of labor and lack of cervical dilatation. Anesthesia was induced with a 10% guaifenesin solution administered intravenously via a pressurized pump followed by intubation and maintenance with 2% halothane. A ventral midline surgical approach exposed the uterus and the fetus was removed through a uterotomy. The placenta was manually stripped from the myometrial edges of the incision and the margins were oversewn using a continuous interlocking pattern. The uterus was then closed using a continuous Utrecht pattern and the uterus rotated 180 degrees back to its normal anatomical position. The abdomen was closed in 3 layers. Recovery of the llama was uneventful with the male cria able to nurse 6 hours post-operatively. Placental expulsion occurred approximately 48 hours after fetal removal.

Local and general anesthetic effects on behavior and performance of two- and seven-week-old castrated and uncastrated piglets.

Four experiments were conducted to examine the effects of general and local anesthetics given prior to castration on piglet behavior and weight gain. The first experiment showed that use of general anesthesia by xylazine, ketamine hydrochloride and glyceryl guaiacolate for 2-wk-old piglets resulted in the death of 28% of the piglets and, for those that survived, suppressed nursing behavior. In the second experiment, using 2-wk-old piglets, local anesthesia by lidocaine hydrochloride prevented the slight (30 min) castration-induced nursing behavior suppression. In the third and fourth studies, using 7-wk-old pigs, local or general anesthetic did not overcome castration-induced changes in behavior. Castration affected behavior of 7-wk-old pigs for 6 to 8 h. None of the treatments in any of the studies influenced weight gain. We conclude that castration is painful for 2-wk-old and 7-wk-old pigs. The 2-wk-old pig seems behaviorally less affected by castration than does the 7-wk-old pig. Local anesthetic prevented pain-induced behavior changes for 2-wk-old, but not for 7-wk-old, pigs. At present, the FDA does not permit use of these anesthetics in meat-producing animals.

Observations following intravenous xylazine administration in steers.

Xylazine was used on 84 occasions to anaesthetise 34 steers, (17 Herefords and 17 Friesians) between 10 and 24 months of age with bodyweights ranging from 209 to 563 kg. Xylazine as a 2 per cent solution was injected intravenously; the mean dose for the Hereford steers was 0.228 mg/kg and for the Friesian steers 0.274 mg/kg. On 21 occasions xylazine only was used. On the other occasions the xylazine was supplemented with local or regional analgesia. The Hereford steers became recumbent after injection of xylazine more readily than the Friesian steers and took longer to recover. In addition the Hereford steers showed fewer reactions to surgical stimulation than the Friesians. It is concluded that xylazine should be supplemented with some form of effective analgesia whenever a surgical operation is performed.