Can dolphins be tranquilized?

[hollian]

It’s my understanding that dolphins (and whales) have no involuntary breathing reflex, so they sleep with half of their brain at a time. So my question is, can a dolphin be tranquilized (for transportation) or put under general anesthesia (for surgery) without killing it?

[JZesbaugh]

Might need a respirator eh?

[Really_Not_All_That_Bright]

This article suggests they can be sedated, but not tranquilized, per se.

[Bear_Nenno]

I used to work at a Dolphin and whale hospital. While it is often repeated that they must sleep with one eye open, I have seen them also sleep with both eyes closed. I read research that showed bottle nose dolphins routinely sleeping for over and hour with both eyes closed. They were completely unresponsive which showed they were definitely asleep. During these periods they perform a tail kick at every breath that ensures they keep their blow hole above the water. Same study mentioned putting the dolphins under general anesthesia. As they slowly slipped from conscious to unconscious, they went from normal breathing, to autonomous breathing with tail kick, to no breathing at all. So they can be put under without killing them. Of course, they will need a respirator just like any other animal would.
As far as sedation for transport, I never saw it performed.

[Magiver]

They’re sedated for travel and are monitored during the process. I have personally seen it done.

[wevets]

Dolphins and other cetaceans can be sedated or anesthetized, as other posters have mentioned, but there are risks to the procedure that are not present in terrestrial mammals.

A good description of the process can be found here

@Lyamin et al. 2008

Dolphin autonomic breathing ceases at the very early stages of anaesthesia, possibly even before they lose the ability to process sensory information. This situation is understandable as the air-breathing aquatic mammal must have a precisely coordinated respiratory action to prevent inhaling water into the lungs while breathing. While anaesthesia in dolphins deepens, the most complex physiological processes are impaired first. Long periods of bilateral high voltage EEG slow wave activity of maximal amplitude are never recorded in dolphins during normal sleep. These episodes can be recorded only occasionally during long breathing pauses and they usually last less than several seconds. As mentioned earlier, diazepam may induce sustained periods of bilateral high voltage slow waves in the EEG; however, it appears that bilateral high voltage delta waves and respiration are not compatible in dolphins. The dolphin fails to respire during bilateral EEG delta waves while lying in slings with the blowhole above the water surface, even if it can move and is trying to take a breath by moving its head and body. Apneas become longer at these times, lasting several minutes, and breaths occur only after the bilateral delta waves in the EEG have disappeared. When a breath is taken, only bilateral desynchronized, bilateral low voltage slow waves or unilateral high voltage EEG patterns (or USWS) have been recorded. After the breath is taken, BSWS develops rapidly. These data strongly suggest that USWS is necessary for autonomic breathing in dolphins during the resting or sleeping periods and indicates that one of the primary proximate functions of USWS is to maintain breathing.

In this passage, USWS refers to Unihemispheric Slow Wave Sleep, a characteristic found in all cetaceans studied [sub]which isn’t actually all that many ;)[/sub] and in the Otariids (fur seals and sea lions,) where the brain hemispheres of the cetacean seem to decouple, with one hemisphere exhibiting the slow EEG waves of low amplitude characteristic of sleep, while the other hemisphere remains active in producing high amplitude EEG waves. In general, the hemispheres seem to switch every so often, and the eye associated with a hemisphere spends more time closed once it enters the slow wave sleep phase.

REM sleep in cetaceans is either non-existent or very very sparse.

There’s also huge problems and an unfortunately high probability of death associated with anesthetizing pinnipeds, and I imagine it’s similar in cetaceans. Sedation by depressing CNS activity works, but care must be taken - where a terrestrial mammal might enter BSWS (Bilateral Slow Wave Sleep,) a cetacean can’t, or if in such a condition must be on an artificial respirator.

[Ostrya]

I don’t know the porpoise of your question but now that you ask, I’d kinda like to know too. Just for the halibut.

[scr4]

@Bear_Nenno

So they can be put under without killing them. Of course, they will need a respirator just like any other animal would.

Are you saying humans would also suffocate if we were administered general anesthesia without a respirator?

[Bear_Nenno]

@scr4

Are you saying humans would also suffocate if we were administered general anesthesia without a respirator?

Kinda hard to breath when your diaphram is in a state of paralysis. That is what intubation is for. I am not an anesthesiologist, so perhaps there are ways to put someone under general anathesia without the need for a respirator. But I don’t believe it is outright wrong to make the assertion that general anasthesia requires intubation and a respirator.

[Bear_Nenno]

@Magiver

They’re sedated for travel and are monitored during the process. I have personally seen it done.

Completely knocked out, or just calmed a little? I never saw it done, but maybe it’s a matter of healthy vs sick animals.

[Skammer]

Years ago I worked for a large public aquarium that had dolphins and whales, and I can confirm that they were sedated for travel but remained conscious.