Relay Barbiturate Toxicity Case Report

Hayley Rasmussen - Washington State

Cases & Abstracts 1st Place Award

In February of 2015 veterinarians were called on emergency to a wild animal sanctuary in Reno, Nevada. The emergency consisted of one wolf found dead, one tiger found unresponsive, and a cheetah found alive but unresponsive. Jamar, a 9-year-old male, castrated cheetah had been at the same sanctuary since April of 2006. When the veterinarian arrived, Jamar was unconscious, hypothermic (not registering by rectal thermometer), tachycardic (180-200 beats per minute), and bradypneic (8-10 breaths per minute).  Mucous membrane color was pink, and capillary refill time was less than two seconds. His eyes were rolled ventral with a very sluggish palpebral response.

Initial treatment was symptomatic and involved warming the patient with appropriate placement of warm fluid bags and blankets, intravenous fluid therapy (emergency replacement at 60 mL/kg for one hour, followed by maintenance level) and dextrose supplementation. At the time of initial treatment, there was a large differential list, including mostly toxic events because of the multiple animal involvement where there was a history of the patients eating a shared meat source.

Blood was drawn to run a complete blood count and serum chemistry panel, while urine was obtained by manual expression so a urinalysis could be performed. The blood work results were unremarkable except for a very mild lymphopenia, hypoproteinemia, and hypernatremia. Urinalysis results were unremarkable as well. An over the counter barbiturate dip-stick test of the urine was positive. A positive OTC urine barbiturate test is not definitive for barbiturate toxicity; however, with the case history and clinical signs this was highly suggestive of relay toxicity in Jamar.

Over the next 72 hours, Jamar was maintained on IV fluids, padded in lateral recumbency, the bladder was manually expressed, and close monitoring of vital parameters was performed.  After the first 36 hours, the heart rate dropped to 120 beats per minute, the respiratory rate increased to 16 breaths per minute, and the pupils became central in location with a faster palpebral response. After about 48 hours, Jamar became slightly responsive to stimuli and was placed in sternal recumbency with padded support. By 72 hours, he was placed in a crate due to increased activity, and he was moved to outdoor enclosure by the 96-hour mark. His initial diet consisted of liquid Ensure, with a slow reintroduction to a regular diet by day six.

Throughout the entire treatment course, complete blood counts and serum chemistry panels were run daily, with no significant changes noted. Jamar experienced no gastrointestinal or urinary tract complications through the course of treatment. At day four, spontaneous urination returned, and passage of feces was observed on day five. Samples of consumed meat and stomach contents of the deceased tiger and wolf were submitted for analysis and came back positive for barbiturates.

            Barbiturates, specifically sodium pentobarbital, are the most common class of drugs used for euthanasia in veterinary medicine due to their ability to produce a rapid and pain free death. The importance of Relay Barbiturate Toxicity is that it may easily be prevented and if caught early, treated successfully. It is critical for veterinary practitioners to be able to successfully place this as a differential diagnosis when appropriate and be able to rule it in or out for rapid treatment. The effects of this toxicity are seen in both scavenging wildlife and household pets, mostly dogs. History of exposure to a euthanized animal is key in obtaining a successful diagnosis. The use of over-the-counter urine barbiturate tests can help in the confirmation of exposure to barbiturates, recognizing that these kits are marketed for humans and suffer from false positives and false negatives when used in our veterinary patients. Successful treatment is supportive based on presentation of the animal. Key to successful prevention is proper disposal of euthanized carcasses. It seems the best ways to achieve this is through composting, immediate deep burial, or incineration.