Diazepam Levels in Foals

The combination of ketamine and diazepam (Valium) commonly comprise anesthesia agents in horses, said Lori Bidwell, DVM, of Rood & Riddle Equine Hospital in Lexington, Ky., at the 2008 American Association of Equine Practitioners convention, held Dec. 6-10 in San Diego, Calif. However, she added, many surgeons steer away from the combination when anesthetizing mares that are suffering from dystocia (difficult birth).

The reason for not using that combination, she said, stems from human reports that diazepam builds in the placenta after the mother receives the drug prior to delivery, resulting in respiratory depression in the baby at birth. However, she said, there have been no published reports that diazepam levels were present in foals after their dams received the combination of ketamine and diazepam.

The purpose of the study conducted at Rood & Riddle, she said, was to determine whether diazepam levels were, indeed, present in foals at birth if the agent had been used to anesthethetize on the dam.

Investigators on the study randomly selected 15 mare/foal combinations from the 57 total cases that arrived at the hospital in 2007 for dystocia treatment. All of them were handled in the same manner. On presentation for dystocia in the hospital, the 15 mares were first given xylazine for sedation. Next they gave the combination of ketamine and diazepam to induce anesthesia, followed by maintaining it with inhalant anesthesia while the surgeon manipulated the foal's position in the uterus to allow delivery. If the foal was not successfully delivered within 20 minutes of presentation to the hospital, the mare was moved into surgery to deliver the foal by Caesarean section.

Two of the 15 foals were delivered by Caesarean section and the other 13 were delivered by controlled vaginal delivery (physical manipulation of the foal in the uterus). The average anesthetic time for controlled vaginal delivery was 13.85 minutes and the average anesthetic time for Caesarean section at the point where the foal was delivered was 37 minutes.

Immediately after delivery blood was drawn from foals and mares and later analyzed. Diazepam was detected in the blood of most mares and foals, but it was almost twice as high in the mares as in the foals.

Thirteen of the foals survived to discharge. One of the nonsurvivors was euthanized because of uncorrectable leg deformities and the other died from hemorrhage associated with fractured ribs (a relatively common occurrence during dystocia birth due to manipulation of the foal through the birth canal).

The average hospital stay for the surviving foals was 5.3 days.

Bidwell summed up the findings this way: "The goal in management of dystocia birth is a healthy mare and foal. Induction of anesthesia for controlled vaginal delivery or Caesarean section should be quick, safe, and effective. The combination of ketamine and diazepam for induction has been used for many procedures in horses, but until now, no studies have researched this combination for dystocia anesthesia. The current study found detectable levels of diazepam in mares and foals after dystocia birth, and average foal levels were 50% of mare values. Although it is difficult to determine whether diazepam levels were associated with ventilatory depression, the diazepam levels in neonates did not seem to negatively affect the outcome of these cases."

About the Author

Les Sellnow

Les Sellnow is a free-lance writer based near Riverton, Wyo. He specializes in articles on equine research, and operates a ranch where he raises horses and livestock. He has authored several fiction and non-fiction books, including Understanding Equine Lameness and Understanding The Young Horse, published by Eclipse Press and available at www.exclusivelyequine.com or by calling 800/582-5604.

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