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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.

Posted by Christa Lesté-Lasserre, MA | May 26, 2020 | Article, Back and Spine, Castration & Gelding, Fractures, Horse Care, Lameness, Ligament & Tendon Injuries, Other Eye Problems, Other Veterinary Technologies, Pain Management, Recovering from Injury & Surgery, Vet and Professional

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.

Researchers and clinicians can operate on standing sedated horses, and the kinds of surgeries they can perform might surprise you. Here are nine standing interventions equine surgeons have used in recent years:

The thought of a conscious, standing horse having a hole drilled into his head or his eye taken out might astound some. But horses undergoing standing surgery are perfectly fine, our sources say.

“They’re relaxed and don’t feel a thing,” Fontenot says. “People used to think it was inhumane but, generally speaking, they’re better off standing sedated than lying down under general anesthesia.”

It’s a procedure that generally leads to fewer complications, more successful results, and/or quicker discharge and recovery, she adds.

“Our data show that complications arising from our procedure itself can be reduced when performed standing,” says Marco Marcatili, DVM, PhD, MRCVS, of the University of Glasgow School of Veterinary Medicine’s Weipers Centre Equine Hospital, in Scotland, and Pool House Equine Clinic, in Lichfield, U.K. His team developed a thyroid removal technique in standing horses.

“We found a lower incidence of recurrent laryngeal neuropathy (a condition known as roaring) in our standing thyroidectomy patients than has previously been reported in patients lying down under general anesthesia,” he says.

Rossignol has noted clear improvements in surgery success rates when performing standing surgeries to treat recurrent laryngeal neuropathy. In addition, his team has recorded significantly less blood loss during standing than recumbent procedures. “There’s just no comparison,” he says.

Generally speaking, standing surgeries also go much faster, says Suarez-Fuentes, who has noted improved speed in performing tenotomies to treat fibrotic myopathy of the semitendinosus muscle (part of the hamstring group) in standing versus recumbent anesthetized horses.

However, he says, his studies haven’t included enough patients to demonstrate reliably whether standing surgeries are actually more successful than recumbent. “It’s hard to compare with low numbers,” he says. “But certainly the standing surgeries don’t seem any less successful.”

These procedures do run a specific risk, however: contamination. It’s more challenging to keep the surgical site disinfected in an awake horse, says Rossignol. “Surgeons really have to learn the art of draping (covering the patient and surrounding areas with a sterile barrier),” he says. “A sedated horse will still move, and whatever drops from his hair or mane during the procedure can contaminate the aseptic area. So extra caution is merited.”

And while horses can potentially lose their balance and fall during a standing surgery under sedation, it’s extremely rare, Suarez-Fuentes says. Plus, clinic staff often stabilize horses in stocks during procedures.

Performing most kinds of surgeries understanding sedation can be less expensive than employing general anesthesia.

“It’s certainly quite a bit cheaper—more or less so depending on the clinic and whether it’s private or academic,” says Suarez-Fuentes.

By eliminating the general anesthesia component and associated staff and shortening the procedure, owners’ costs can drop to “a fraction of the procedure cost with general anesthesia,” says Fontenot.

“This also has a real welfare effect in an indirect way,” she adds.

“A lot of horses belong to owners who just don’t have the money for expensive procedures,” she says. “Standing sedation sometimes brings these procedures into the realm of being affordable, allowing horses to have access to veterinary care they wouldn’t otherwise have had.”

But reduced costs aren’t the case across the board, says Rossignol. “Standing surgeries are complex in their own right and have their own technical challenges, so we still need the time and staff to do them well,” he says. “That can result in similar costs.”

Hospitalization can last as long as that required for a recumbent surgery, since the clinic stay is “based on the kind of surgery, not the kind of anesthesia,” he says.

Even so, the reduced risk of complications and higher success rate of certain standing surgeries can translate into economic advantages for the owner, even when the initial procedure price is the same, Rossignol says.

A fringe benefit of standing surgeries is that they can be more comfortable for the surgeons themselves, our sources say. “Sometimes it’s just so much nicer for us to be able to operate without having to lean over or twist our necks a certain way throughout the length of the procedure,” Fontenot says.

But what’s comfortable and convenient for one surgeon can be the opposite for another, often depending on what’s familiar. “Some surgeons have a set system and large staff to assist them,” says Suarez-Fuentes. “Others are happy to try the standing technique and get used to things being so different for them compared to a recumbent surgery.”

In exceptional cases, standing surgery can be more dangerous for the veterinarian than recumbent surgery, says Fontenot. “I’ve known some who won’t do standing procedures anymore because they’ve had their own femurs fractured by an uncooperative patient,” she says. “It’s rare, but it can happen. Even a sedated horse can kick with surprising accuracy.”

Many surgeries absolutely require general anesthesia: most colic surgeries, including large intestinal volvulus and small intestinal strangulating lesions; cesarean sections; complex fractures; and arthrodesis (permanent surgical immobilization of a joint). So it would be inaccurate to give the impression that standing surgeries are universal, near-flawless solutions to operating on horses. Also, while the process works well for many kinds of surgeries, it’s not a perfect fit for all patients. “The temperament of some horses may mean they’re unsuitable candidates,” says Marcatili.

Suarez-Fuentes agrees. “Horses that don’t cooperate during sedation or when we’re performing the local anesthesia have to be operated on under general anesthesia, because otherwise it’s not safe for the staff, nor for the horse,” he says.

Fontenot says if she and her team have time, they try to work with difficult horses first to train them to accept the procedure under sedation. But, even then, some horses aren’t amenable and standing surgeries aren’t always possible. “You have to put safety first,” she says.

Furthermore, even when veterinarians opt for standing surgery, things could change along the way, she says. “We warn owners that we might have to switch to general anesthesia to finish up if the horse is uncomfortable or reacting strongly.”

Standing surgeries in sedated horses are becoming more popular and well- defined in scientific studies, our sources say. The benefits are clear—the procedures can provide good, if not better, results than equivalent surgeries on fully anesthetized horses, without the added costs and complications. Plus, they often allow surgeons to work in a “realistic” environment—with the horse and all its heavy tissues in their real-world upright alignment. While it runs its own share of risks, they’re usually minor and rarer than the ones associated with recumbent surgery under general anesthesia, they say. As researchers continue to expand the reach of standing, sedated surgery options, owners and horses alike stand to benefit from its health, welfare, and financial benefits.

Passionate about horses and science from the time she was riding her first Shetland Pony in Texas, Christa Lesté-Lasserre writes about scientific research that contributes to a better understanding of all equids. After undergrad studies in science, journalism, and literature, she received a master's degree in creative writing. Now based in France, she aims to present the most fascinating aspect of equine science: the story it creates. Follow Lesté-Lasserre on Twitter @christalestelas.

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