Many medical procedures are performed while the horse is under standing chemical restraint, but anesthesia in horses can be risky. One study cites an almost 2% mortality rate for equine patients within seven days of receiving general anesthesia.

“It may be especially difficult to correctly dose sedative drugs in very old or debilitated patients. Similarly, very anxious or excited horses may require very high doses of drugs that could simultaneously interfere with a horse’s ability to remain standing,” said Robert J. Brosnan, DVM, PhD, Dipl. ACVA, of the University of California at Davis.

Once the procedure is finished, excessive sedation might persist, making it difficult for the horse to stand and requiring more drugs to reverse its effects. Brosnan and Eugene P. Steffey, VMD, PhD, Dipl. ACVA, examined the effects of propofol, a short-acting anesthetic, as an equine sedative. They found that it was not useful alone, but might be useful when combined with other drugs.

Short-acting anesthetics might be safer because they give the veterinarian greater control over the depth and duration of the sedation. Although low doses of propofol in horses causes short periods of sedation, which is desirable, higher doses can cause excessive stumbling, muscle weakness, and possibly excitement, according to Brosnan