Standing surgeries on sedated horses can provide good, if not better, results than equivalent surgeries on fully anesthetized horses, without the added costs and complications. Read an excerpt of this feature from our May 2019 issue of The Horse now.
Surgeons can perform an increasing number of procedures on standing sedated horses
A horse lies on a massive surgical table, blue drapes covering much of his body and surgical scrub booties over his hooves. Anesthesia equipment hums as the surgical team works efficiently and expertly in their various roles to complete a procedure. This is the classic equine surgery scenario, which is necessary for most colic cases and a variety of other procedures.
However, there are many surgeries that can be performed in the standing horse. From simple castrations to more complex procedures such as ovary removal and repair of simple fractures, researchers are recognizing the benefits of standing surgeries and, say our sources, pursuing them more frequently. In any type of surgery, a variety of circumstances dictates which approach—standing or recumbent (lying down)—a veterinarian will choose.
Regardless of the species, general anesthesia (induced, controlled complete loss of consciousness) has its risks, primarily associated with side effects of the drugs used to keep the patient unconscious. Because of their size and their nature, horses face even greater risks, say our sources.
“Most horses do really well, but a very low percentage might develop issues like myopathies (muscle diseases), neuropathies (nerve damage), or laryngeal collapse,” says David G. Suarez-Fuentes, DVM, of BluePearl Veterinary Partners, in Tennessee, who studied standing surgeries at Iowa State University College of Veterinary Medicine, in Ames.
This is mainly due to horses’ sheer mass, he explains. When a horse is placed on his side or back for surgical procedures, his weight compresses the muscles and airways and can possibly interfere with circulation. And the heavier the horse, the worse it can be.
“That’s really not a natural position for them to lie in for hours at a time without moving, and their muscles can literally get crushed, leading to tying-up (the breakdown or destruction of skeletal muscle cells, causing trembling, sweating, and refusal to move) or even nerve paralysis,” says Robin Fontenot, DVM, MS, Dipl. ACVS-LA, assistant clinical professor (equine) in the Department of Clinical Sciences at Mississippi State University’s College of Veterinary Medicine, in Starkville. What’s more, horses’ flight instinct puts them at risk of self-injury during recovery, Fontenot says. Disoriented and scared, horses can come out of anesthesia ready to bolt but lacking the coordination for safe movement. “They can fracture their limbs or facial bones, bite their tongues, get soft tissue injuries, and even injure the surgical site,” she says. “Of course, we plan for that and try to help them avoid it, but you can’t always control it.”
Getting around general anesthesia altogether is a good way to avoid these risks, our sources say. Providing an equine surgical patient with medicated sedation that allows him to be “drowsy” without having to lie down, along with local anesthesia (numbing where pain is likely to occur) at the surgical site, circumvents such risks.
A completely anesthetized horse’s internal parts get compressed while on his side. So standing upright offers a major advantage in many kinds of surgeries, our sources say.
“Getting in the throat for operations like laser cautery of the larynx, tiebacks, and laryngeal reinnervation is greatly simplified when the horse is standing sedated because the horse is in his exact natural position,” says Fabrice Rossignol, PhD, DVM, Dipl. ECVS, equine surgery specialist at the Grosbois Equine Clinic, in Boissy Saint Léger, France.
This arrangement makes it easier to identify, manipulate, and work with the target structures, he says. It also conserves the tissues’ natural feel—which could change under the pressure of other tissues in a lying position. “They’re a lot more supple and easier to work with,” he says.
Also for head or throat conditions, with standing surgery the horse doesn’t need to have a tube placed down his trachea, Rossignol adds. “Obviously, that tube can get in the way, so eliminating it is a clear advantage.”
Suarez-Fuentes finds similar benefits when performing tenotomies—therapeutic slicing of tendons—partly because standing keeps the tendon in its normal state of tension. “The standing position lets us palpate the tendon better and recognize anatomical landmarks more easily, helping ensure the procedure is done correctly,” he says.
Positioning is also improved for operations in other regions, especially the sinuses and the pelvic area. “For ovariectomies and cryptorchidectomies (removal of ovaries and retained testicles, respectively), for example, access is greatly facilitated because the intestines all fall naturally underneath,” Rossignol says.
As a finishing touch, the standing position allows surgeons to “test” their work in more natural conditions, he says. Once they’ve completed their procedure, they can make sure structures line up and function correctly. The fact that the horse is awake and, even under sedation, can move and breathe, makes this testing—as well as any necessary adjustments—more reliable before closing up the surgery site.