Anesthetic effects of tiletamine-zolazepam, alone or in combination with butorphanol, in goats.

OBJECTIVE

To evaluate anesthetic effects of tiletamine-zolazepam (TZ), alone or in combination with butorphanol, in goats undergoing laparotomy for embryo collection.

DESIGN

Randomized clinical trial with crossover design.

ANIMALS

9 adult female goats.

PROCEDURE

Goats were anesthetized twice: once with TZ (5.5 mg/kg [2.5 mg/lb] of body weight, i.v.) and once with tiletamine-zolazepam and butorphanol (0.1 mg/kg [0.045 mg/lb], i.v.). Additional doses of TZ (0.5 to 1.0 mg/kg [0.23 to 0.45 mg/lb], i.v.] were administered as needed to maintain a surgical anesthetic plane. Time to sternal recumbency was recorded, and quality of induction was scored. Arterial pressures, heart rate, respiratory rate, and rectal temperature were recorded every 5 minutes; arterial blood samples were collected every 30 minutes. Oxygen was insufflated if estimated saturation of hemoglobin in peripheral arterial blood with oxygen was < 90%; intermittent positive-pressure ventilation was performed if goats became apneic. Muscle relaxation, quality of anesthesia, and eye signs were scored every 15 minutes during anesthesia. Anesthesia time was recorded, and quality of recovery and degree of postoperative analgesia were scored. Plasma cortiso concentration was measured before induction, immediately after extubation, and 2 hours after extubation.

RESULTS

Induction was rapid and smooth. Five goats regurgitated, 3 required supplemental oxygen, and 1 required intermittent positive-pressure ventilation, but none of the goats became hypotensive. Muscle relaxation and quality of anesthesia were adequate. Goats recovered from anesthesia without complications. We did not detect any significant differences between anesthetic regimens for any of the variables measured, except bicarbonate concentration and base excess.

CLINICAL IMPLICATIONS

TZ at a dose of 5.5 mg/kg was satisfactory for anesthetic induction in goats; additional doses can be given to extend anesthesia time, but addition of butorphanol at a dose of 0.1 mg/kg to this regimen does not seem to provide any measurable benefit. An oxygen source and a means of assisting ventilation should be available.