With the recent trend of intraorgan euthanasia methods on the rise in animals as reported by the Companion Animal Euthanasia Training Academy (CAETA), I want to offer useful pointers on how to ensure unconsciousness and avoid pain. If you are new to the concept of giving pentobarbital (euthanasia solution) in locations other than veins, the goal is to infuse pentobarbital into areas of the body with good blood flow, e.g., heart, liver, kidney. The organ’s vasculature will move the drug to the brain to cause a rapid shutdown of all body systems including permanent death. Because pentobarbital is a highly alkaline substance and needles in organs are known to be painful, all patients must first be made unconscious and unaware (1,2). The important question becomes, how do we know they are ready for us to proceed?

There are many factors to consider before attempting euthanasia in animal patients, and the method is determined by veterinary teams, shelter staff, and researchers. Such factors include:

• Their experience with different techniques
• The presence of onlookers
• What types of drugs are available
• Use of pre-euthanasia sedation or anesthesia
• The signalment/health of the patient
• What medical equipment is handy
• The need for a postmortem exam (necropsy)

When it comes to intraorgan euthanasia injections, the requirement is that the patient must first be given anesthetic drugs to induce unconsciousness. Examples of such drugs include ketamine, tiletamine, and alfaxalone. These are all anesthetic drugs that, when given in proper doses, will render the animal patient unaware of the pentobarbital euthanasia injection into an organ. To put it more succinctly, unaware = unconsciousness = no pain. The practitioners overseeing the injection must determine if the anesthetic drug dosages are high enough to prevent the patient feeling anything. It is common for ketamine, tiletamine, and alfaxalone to be given in combination with sedatives like dexmedetomidine, butorphanol, and acepromazine to boost deeper sleep. They are given into the muscle or under the skin, and after 5-10 minutes, the patient is assessed for unconsciousness before pentobarbital is given.

So how do we know when our patients are unconscious and ready for an intraorgan injection? We read their body cues. Unless the veterinary team has access to devices that measure brain activity, e.g., electroencephalogram (EEG), observing and feeling the patient’s body is the most practical approach. Breathing changes, muscle tension/relaxation, eye movements, and pain tolerance are what we watch for. As an animal succumbs to anesthetic drugs, there are patterns of physical change we expect. It’s important to know how these drugs work in the body to predict alterations. For example, tiletamine is known to cause lip licking, head weaving, and increased sensitivity to noises in patients, before they lay their body down to sleep. The trained eye will pick up on this. Eventually the patient will be unresponsive to noises and simple touch, and then the real tests begin.

Patients that look unconscious need to be tested for any reactivity and most importantly, pain. The goal in assessing a sleeping patient is to try and make them respond to whatever you are doing to them. If they respond, they are still sensible and aren’t yet ready for an intraorgan euthanasia injection. 

Methods for Testing Consciousness in Patients Before an Intraorgan Euthanasia Injection

1. Give strong, significant pinches in between the toes and sensitive areas, e.g., ear flaps, inner thigh, lip. Use fingernails to pinch extremely hard, mimicking what a hemostat clamp might do.
2. Check for abdominal muscle tensing. There should be no tensing of any muscles, including when the body is shifted or repositioned in preparation for the euthanasia injection. 
3. Use clippers to shave legs for venous access. Patients should not lift their head or move their eyes when clippers are being used.
4. Raise the tail above the back. If unconscious, the patient will leave the tail where you place it rather than moving it down.

Everything we do to test for consciousness should be subtle for the client. They will see their pet’s body being touched but not in offensive or startling ways. In other words, pinching and testing for pain is a private affair. It takes a bit of finesse to make pinching look gentle but it can be done. When the patient is ready, the intraorgan euthanasia injection can begin. If they are not, it’s time to give more anesthetic drugs until they are. Reliable unconsciousness is worth waiting for.

References

1. Cooney, K, et al. (2012). Veterinary euthanasia techniques : a practical guide. Wiley-Blackwell.
2. Leary S, et al. 2020 edition. AVMA Guidelines for the Euthanasia of Animals. https://www.avma.org/sites/default/files/2020-02/Guidelines-on-Euthanasia-2020.pdf Accessed Feb 19, 2024.