Repetitive injectable anesthesia in a 27-year-old horse.

The research describes a case study of repeatedly anesthetizing a 27-year-old horse three times a week for a month, to facilitate cobalt therapy on a squamous cell carcinoma in the sinus. Despite possible complications due to age and nature of the treatment, the horse tolerated the anesthetics well without observable complications.

Case Briefing

• The research presents a unique case of a 27-year-old horse undergoing repetitive injectable anesthesia to facilitate cobalt therapy (a type of radiation therapy) for a squamous cell carcinoma in its left paranasal sinus.

Setup and Procedure

• Due to limited facilities, the anesthetized horse had to be transported between the cobalt therapy room and its stable, necessitating the use of injectable anesthesia.
• At first, the horse was preanesthetized with xylazine (at 1.1 mg/kg IV) and butorphanol (0.04 mg/kg IV). This cocktail was used to sedate and anesthetize the horse to minimize discomfort and stress.

Anesthetic Revision

• After three anesthetic episodes, adjustments were made to the the regimen. The xylazine dose was reduced to 0.4 mg/kg IV, and butorphanol was removed entirely from the anesthetic mix.
• Tiletamine-zolazepam (1.1 mg/kg IV) was used for both induction (the initiation phase) and maintenance (the operational phase) of anesthesia, although on two occasions, a bolus of ketamine was also used to maintain immobility.

Treatment Duration and Recovery

• The lengths of the cobalt therapy procedures varied from 10 to 45 minutes.
• Recovery times varied as well, with the time to sternal (lying on the chest) being 23 to 76 minutes, and the time till standing ranging from 55 to 105 minutes.

Outcome Analysis

• Despite concerns of potential complications due to age and the physiological stress of repetitive injectable anesthesia, none were observed in the horse.