• Anesthesia
• Veterinary Medicine
• Working Animals & Livestock

• Anesthesiology

Hans Coetzee, PhD, Iowa State University, Ames, Iowa, USA, gave an overview of multimodal analgesia in large animal field restraint. The opioid nalbuphine has several advantages as an alternative to butorphanol. Because nalbuphine is an opioid k agonist/μ antagonist, it has very low abuse potential. It is currently a nonscheduled drug in the United States except in Kentucky where it is scheduled because of abuse potential in equines. It is also less expensive than butorphanol, costing $2.50 per mL compared with $8.60 per mL for butorphanol. In addition, its use is not associated with any cardiovascular, respiratory, or gastrointestinal adverse effects. All opioids, including nalbuphine, have very short half-lives in ruminants. “Opioids in my experience have not necessarily been my mainstay analgesic drug when it comes to ruminants. I use them as an adjunctive therapy in combination with xylazine and ketamine,” Dr. Coetzee said.

The Ketamine Stun is a combination of the dissociative anesthetic ketamine and the α-2 agonist xylazine, with butorphanol added if needed. For large groups of cattle, a stock solution for a standing stun can be made (Table 1). This solution should not be stored for future use.

This combination can be modified if a recumbent stun is needed, as follows: xylazine 0.025 to 0.05 mg/kg (same as standing stun), butorphanol 0.05 to 0.1 mg/kg (10x standing stun), and ketamine 0.3 to 0.5 mg/kg intravenously (IV; 5 × standing stun). Animals become recumbent gracefully in approximately 1 minute and the effect lasts for 15 to 25 minutes. For 15 minutes of anesthesia, xylazine 0.05 mg/kg IV is administered first followed by ketamine 2 mg/kg IV (20 × standing stun) once sedated. In cases where longer anesthesia is required, the combination of xylazine 0.05 to 0.1 mg/kg intramuscularly (IM) and ketamine 4 mg/kg IM provides 30 to 40 minutes of recumbency. Animals do not need to be fasted before the standing stun or recumbent stun, but should be fasted 24 to 48 hours before anesthesia.

Dr. Coetzee also provided some alternatives to xylazine alone. Romifidine 0.05 mg/kg can be used for recumbency in sheep and a dose of 2 to 3 mg IV provides excellent standing restraint in adult cows. Detomidine 2.5 to 10 μg/kg IV provides sedation and recumbency in cattle lasting 30 to 60 minutes. Medetomidine at a dose of 30 μg/kg IM produces recumbency in calves and a dose of 10 μg/kg IV produces recumbency in sheep for approximately 1 hour.

The acidic properties of lidocaine produce a painful injection in animals. Because of this, Dr. Coetzee highly recommends the use of lidocaine buffered with sodium bicarbonate, using a 10:1 ratio of 2% lidocaine to a commercially available 8.4% sodium bicarbonate solution. This practice is supported by published reports that buffered lidocaine reduces injection pain [McKay et al. Anes Analg 1987], may enhance analgesia [Curatolo M et al. Anes Analg 1998], and may reduce nerve block onset time [Sinnott CJ et al. Anethesiology 2000].

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