Have you used ketamine as premedication in Dogs and Cats? Really? - NAVE Discussion #3

In this video, we will discuss a bit about the use of ketamine as a sedative in preanesthetic medication for dogs and cats. This practice has been common among vets, but do we really achieve sedation with ketamine?

If we consider the main effect of preanesthetic medication, which is sedation, ketamine won't help us. It actually promotes cerebral depression, mainly in the cortex, reducing sensations of touch, pain, vision, and temperature. However, other areas are stimulated, especially the limbic system, which is related to emotions. So, with the use of ketamine, we have stimulation of some parts of the brain and inhibition of others. Additionally, it does not promote muscle relaxation; on the contrary.

It's true that those who use ketamine in preanesthetic medication administer much lower doses than those that would cause dissociative anesthesia. However, there are few studies that have evaluated the efficacy of ketamine in "subanesthetic" doses as a sedative. In a study in dogs , where they received 3 mcg/kg of dexmedetomidine + 0.3 mg/kg of methadone and 1 or 2 mg/kg of ketamine, the authors found that sedation worsened in animals that received ketamine, with some animals showing drooling and dysphoria, clearly demonstrating the psychomimetic effects of this medication.

On the other hand, in a recent study with cats (Pinho, 2024) who received 7 mcg/kg of dexmedetomidine + 0.3 mg/kg of methadone + 1 mg/kg of ketamine, the addition of ketamine was beneficial, promoting intense sedation in the animals, with none of them showing psychomimetic effects. An important factor is that they used docile, easily handled cats. This certainly could have influenced the results.

That's a good point. In feral cats, it's often challenging to handle them without ketamine. However, when using higher doses, it's no longer preanesthetic medication but rather chemical restraint or almost dissociative anesthesia.

I believe that if we use the medications commonly used in premedication, such as phenothiazines, alpha 2 agonists, and opioids, especially combined, we can achieve adequate sedation in dogs and cats without the need to dissociate the animal. However, it's worth remembering that we need to maintain a quiet environment and give time for the drugs to take effect.

But I agree that this approach is widely carried out nowadays... and it will depend on how the professional sees it. I'm just discussing here the effect of ketamine as a sedative... what it doesn't promote...

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Read also about:

• Dissociative Anesthesia - Anesthesia Unravelled #11
• Dissociative Anesthetics - NAVE Answer!
• Beyond dissociative anesthesia: Ketamine as an analgesic adjuvant.

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Find out more:
– Arenillas et al. Sedative and analgesic effects of two subanaesthetic doses of ketamine in combination with methadone and a low dose of dexmedetomidine in healthy dogs. Vet Anaesth Analg, 48:545-553,2021.
– Pinho ISR. Influência de uma dose subanestésica de cetamina sobre o grau de sedação, variáveis fisiológicas e dose de propofol em gatos premedicados com dexmedetomidina e metadona: estudo clínico, prospectivo e randomizado. UFRGS. PPG em Ciências Veterinárias. Dissertação. 2024, 31p.

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