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Every so often I come across these odd news stories detailing strange tales of dogs and cats who somehow managed to cheat euthanasia. Like the Rottweiler who “awoke” and came wandering into the living room after being euthanized by his veterinarian in the garage. Then there’s the account of the homeless cat who survived not one but two trips to the carbon monoxide gas chamber before shelter workers decided that killing her wasn’t such a good idea.
Inevitably, these reports whip pet owners everywhere into a froth of well-justified righteous indignation coupled with understandable bewilderment: “How, exactly, can a veterinarian allow that to happen? How could they not know whether she’s dead or not? Could this happen to my pet?”
Such strong reactions help explain how these seemingly annual news events trigger not just the ire of the public, but discussions on the merits and pitfalls of various euthanasia methods too. Which, as you might expect, also raises the unavoidable misconceptions concerning the mechanics of euthanasia and how the drugs employed to bring it on actually work.
That’s why it behooves us veterinarians to always make plain the euthanasia methodology we intend to employ. Because when it comes to something as emotionally fraught as euthanasia, there’s no such thing as too much communication.
So at the risk of overloading you with information, here’s an explanation of the most common method of euthanasia private veterinarians employ in their practices with explanations about the drugs that are typically involved:
But before we go there, let me first explain the goal, as described by the American Veterinary Medical Association’s Guidelines For the Euthanasia of Animals (2013):
“When euthanasia is the preferred option, the technique employed should result in rapid loss of consciousness followed by cardiac or respiratory arrest and, ultimately, a loss of brain function. In addition, animal handling and the euthanasia technique should minimize distress experienced by the animal prior to loss of consciousness.”
The Two-Injection Method
With that in mind, the currently favored method of achieving this goal in veterinary private practice settings is the so-called “two-injection method.” In this approach, an initial injection goes either in the vein (intravenous) or in the muscle (intramuscular), to elicit extreme sedation. Once sedation is accomplished (typically rendering a pet both completely unresponsive and thoroughly insensate) a second drug is then administered (typically as an intravenous injection) to overdose the animal and achieve cardiopulmonary arrest.
Both injections are technically considered “overdoses” of drugs we either currently use or historically have used in veterinary practice for sedation, tranquilization, analgesia and/or anesthesia. But it’s important to note that not every veterinarian uses the same drugs in the same way at the same doses.
Indeed, while the two-injection method may be the modern gold standard approach to euthanasia, there’s a surprising degree of variability when it comes to the drugs employed in the process and it’s impossible to detail them all here.
Here is a brief run-down of the most common drugs we use, categorized by their use as first or second injection drugs.
The goal: profound sedation or complete anesthesia with a minimum of pain or stress related to medical techniques or handling).
Common drugs used include:
- Tiletamine/zolezepam (Telazol®) is a pre-mixed cocktail of two drugs (tiletamine and zolazepam), which is employed commonly as a tranquilizer for both cats and dogs. Tiletamine is technically considered a dissociative anesthetic and zolazepam is a valium-like anti-anxiety drug. Neither drug is very pain-relieving by itself and yet, when combined, they lead to an extremely effective sedation that approximates complete anesthesia. When administered as an overdose as part of euthanasia, a state of complete anesthesia results.
- Ketamine is a dissociative anesthetic which is most often combined with valium to produce the same effect as tiletamine/zolezepam. Ketamine, however, has some additional pain-relieving effects, which makes this combination preferable to some veterinarians for routine use during certain medical procedures. As an overdose, however, as in the case of euthanasia, the differences between ketamine/valium and tiletamine/zolezepam are considered minuscule.
- Propofol is another drug we use commonly to induce anesthesia. The problem is that propofol (nicknamed “milk of amnesia” for its white color) is expensive compared to the above two alternatives. Still, it’s highly effective and commonly employed in the two-injection euthanasia protocol.
Note: The above drugs are most often delivered intravenously for euthanasia. That’s because propofol is an intravenous-only drug and both tiletamine/zolazepam and ketamine/valium may smart when delivered in the muscle. Nonetheless, a brief sting is considered acceptable by many vets (indeed, I use it as such in certain scenarios). But the biggest benefit of intravenous injection is the speed of action; most animals are deeply “asleep” within seconds.
- Dexmedetomidine: Marketed Dexdomitor by Zoetis, this drug is excellent to induce a pain-relieving sedation with a sting-less intramuscular injection for dogs. Mixed with opiates and other drugs, it also works well for painless intramuscular injection in cats.
- Acepromazine or “ace,” as it’s commonly referred to in vet circles, is a tranquilizer commonly used in veterinary practice to chill out aggressive or extremely active dogs. Ace is popular for its low cost and low human abuse potential. Some animals react to the sting of the needle when delivered intramuscularly, but it can easily be included in IV preparations.
- Xylazine is includes in many first-injection cocktails. It’s most commonly used as a tranquilizer in horses but it’s an inexpensive and highly-effective choice for overdosing small animals as part of the first injection.
Misconception alert: None of these drugs causes an “awake” form of paralysis you may have heard about. Many owners fear this but, rest assured, we are not merely rendering animals motionless with our choice of first injection drugs. Nothing less than a profound sedation with complete anesthesia is the goal of this stage.
The goal: cardiac arrest and respiratory arrest followed by a complete loss of brain function)
- Barbiturates are employed by almost all companion animal veterinarians as the second injection in the two-injection protocol or sometimes as the sole injection. Many different preparations of barbiturates are used to overdose animals quickly. These are almost always given intravenously for rapid onset of cardiac arrest (within fifteen to sixty seconds in most cases).
Sometimes, however, if the first injection is extremely effective (as it is designed to be), intracardiac (directly into the heart) injection is considered a humane alternative. This usually happens when the intravenous route becomes complicated by any condition that limits a veterinarian’s ready access to the veins. But here’s the thing: Intracardiac injections of drugs are painful and should NEVER be administered to an animal that is not anesthetized or verifiably unconscious.
An intraperitoneal injection (directly into the abdomen) of barbiturates in a conscious animal is, however, considered a humane method according to the AVMA’s guidelines. Nonetheless, it’s much less frequently undertaken than the intravenous route due to a) the long period of time before pets succumb and/or b) the disagreeable appearance of the process.
Whichever the approach, barbiturates, if dosed properly, lead irrevocably to death. Once the heart stops and respiration ceases, loss of brain function quickly follows. Owners nervous about this process who want to feel as certain as they can be that their pet has passed are always free to sit with their pets for a reassuring period of time.
I know this is a long post and you’ll no doubt have LOTS more questions but here’s hoping this post will at the very least help set your mind at ease about some of the medical issues you might not understand or may have misgivings about –– especially those that might naturally arise after hearing news reports about “incomplete” euthanasia.