For the first time, hemodialysis has saved the life of a horse with silver maple toxicosis.

The Quarter Horse mare arrived at the Ohio State University clinic about 12 hours after beginning to show signs of maple poisoning.

The wilted leaves of certain maple trees—red, sugar and silver—contain toxins that damage the hemoglobin in red blood cells. This limits their ability to carry oxygen to tissues throughout the body. The toxins also cause destruction of red blood cells, which results in waste products that damage the kidneys. Affected horses become lethargic and develop rapid heart and respiratory rates. Other typical signs of maple poisoning are dark red gums and coffee- colored urine.

With supportive care, which includes intravenous fluids, steroids and—sometimes—blood transfusions, about 50 percent of horses with maple leaf toxicity survive to discharge from the hospital.

One of the most devastating effects of maple leaf toxicity is acute kidney injury. And, until now, there have been no reports of successful hemodialysis in an adult horse with acute kidney injury. “The mare described in this case report was stabilized using several medications and a blood transfusion,” says Erin Pinnell, DVM. “After a few days of medical management and supportive care, however, her kidney values were still elevated. That is when hemodialysis was offered.”

When hemodialysis can help

In hemodialysis, a machine filters wastes from blood when kidneys are too damaged to do this work. “Basically, the blood from the patient is removed and goes into the hemodialysis machine via an intravenous catheter,” explains Pinnell. “In the machine, the patient’s blood is separated by a semipermeable membrane that allows bad uremic toxins to be removed. These are then replaced with the good solutes that the patient needs. This allows the kidneys to heal while filtering out toxic solutes that have accumulated in the blood.” In people, hemodialysis may be done briefly to treat acute kidney injury or regularly in cases of chronic kidney disease.

Although sometimes used in small animal medicine, hemodialysis is rarely done in horses. “It has been performed in equine foals with kidney injury successfully,” says Pinnell. “It was completed in a group of healthy horses prior to this case report, but it is not a typical treatment.” After consultation with clinicians experienced in hemodialysis on small animals, the Ohio State team prepared the mare for what would eventually be two treatments.

Successful treatment

“The mare was sedated initially but tolerated the procedure very well both times,” says Pinnell. “She was placed in the stocks and had hay available during the entire treatment, which took about six to eight hours each. No complications or problems occurred during the procedure. The mare stood happily and enjoyed her snacks during her treatment times.”

After the second treatment, the mare’s kidney values improved so much the team decided she didn’t need a third. “Her BUN and creatinine (markers of how well the kidney is functioning) were almost normal after her second treatment. They gradually continued to decrease to normal without further treatment following the second round of hemodialysis.” The mare made a fully recovery.

Based on this case, Pinnell says hemodialysis is a viable treatment option for horses. “If the horse is suspected to have an acute kidney injury and first-line supportive care is not effective, hemodialysis could be an option,” she says. However, Pinnell adds, it would not be practical to keep a horse with chronic kidney disease on hemodialysis at this time.

Reference: “Successful hemodialysis treatment of a Quarter Horse mare with silver maple leaf toxicity and acute kidney injury.” Journal of Veterinary Internal Medicine, April 2024.