Best Practices for 20 Minutes of Equine Field Anesthesia

Best Practices for 20 Minutes of Equine Field Anesthesia

“Good footing is necessary for horses during recovery,” Hubbell said, and a minimum 4-by-4-meter area free of obstructions is also necessary for a safe recovery.


Every week, about half of all equine veterinarians anesthetize horses for procedures that take no more than 20 minutes to perform. Because these horses are under for only a short period of time, veterinarians commonly carry out such procedures in the field rather than in a hospital or clinic setting, said John Hubbell, DVM, Dipl. ACVAA, of The Ohio State University School of Veterinary Medicine.

A board-certified veterinarian anesthesiologist with 35 years of experience, Hubbell presented his recommendations in a lecture at the 2013 American Association of Equine Practitioners’ Convention, held Dec. 7-11 in Nashville, Tenn.

Any time veterinarians put animals under anesthesia, there’s risk involved, Hubbell said. But for horses the possibility for problems is greater than it is for other species. For example, it’s estimated that one out of 100 horses might die under anesthesia, he said; in comparison, only one out of 1,000 dogs or cats die under anesthesia.

To minimize or identify risk prior to surgery, Hubbell stressed to the veterinary audience that they should complete blood work (prior to day of surgery), collect a full patient history, and perform and record a physical exam prior to anesthesia induction. “Preanesthetic blood work does not need to be extensive for short procedures,” he said.

Veterinarians should also secure complete written owner or agent permission prior to anesthesia, Hubbell advised. Additionally, he recommended that all field veterinarians have oxygen on their trucks for emergency ventilation and use intravenous catheterization to ease drug administration and reduce injection-related manipulation and stimulation.

He further stressed that during procedures veterinarians should observe and record the anesthetic drugs they administer and their effects, as well as record the horse’s minimum heart rate and respiratory rate at 5- to 10-minute intervals.

Hubble said more than 90% of equine veterinarians use ketamine (a common veterinary anesthetic) as the primary drug for short-term anesthesia. Veterinarians sometimes use a combination of ketamine and xylazine (another common sedative) for anesthesia. While this technique has been proven to be safe for use in horses, Hubbell noted some problems researchers found that practitioners should be aware of:

  • Inadequate sedation before ketamine administration producing induction failure;
  • Inadequate muscle relaxation during recumbency (while the horse is down); and
  • Too short a duration of anesthesia.

Many veterinarians use the sedatives diazepam or midazolam in addition to ketamine to augment muscle relaxation, Hubbell said.

Two additional sedative drugs that are approved for use in U.S. horses include detomidine and romifidine, he said. Either can be substituted for xylazine for sedation prior to induction of anesthesia, he said.

Another risky period for the horse is during post-anesthesia recovery, when horses can struggle to regain their feet. This is the most common cause of injury to horses undergoing anesthesia, Hubbell cautioned.

“Good footing is necessary for horses during recovery,” he said. “Grass turf or most sand arenas work.” A minimum 4-by-4-meter area free of obstructions is also necessary for a safe recovery, he added.

The horse should wear a halter and lead rope so an experienced handler can control the animal once it stands. “Position the horse in lateral recumbency,” Hubbell recommended. “Most horses will roll to sternal recumbency within 45 minutes and stand shortly after.”

In most instances it is better to wait for the horse to decide to stand rather than attempt to rush it to its feet, he said.

Take-Home Message

Short-term anesthesia for procedures lasting fewer than 20 minutes is common field work in equine medicine. An experienced veterinarian who takes precautions prior to, during, and after anesthesia can reduce the likelihood of complications and even death.

About the Author

Michelle N. Anderson, Digital Managing Editor

Michelle Anderson serves as The Horse's digital managing editor. In her role, she produces content for our web site and hosts our live events, including Ask the Vet Live. A lifelong horse owner, Anderson competes in dressage and enjoys trail riding. She's a Washington State University graduate (Go Cougs!) and holds a bachelor's degree in communications with a minor in business administration and extensive coursework in animal sciences. She has worked in equine publishing since 1998. She currently lives with her husband on a small horse property in Central Oregon.

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