Emergence delirium following dog castration - reflection - any advice how to reduce risk and control if it occurs

RE: Emergence delirium following dog castration - reflection - any advice how to reduce risk and control if it occurs

Benjamin Alyoshkin — Thu, 07 Jan 2021 13:25:30 GMT

Hi Richard, intriguing, thank you very much!

RE: Emergence delirium following dog castration - reflection - any advice how to reduce risk and control if it occurs

Benjamin Alyoshkin — Thu, 07 Jan 2021 13:24:02 GMT

Hi Karl, thank you very much indeed for your thoughts! PS Leahurst 2012?!

RE: Emergence delirium following dog castration - reflection - any advice how to reduce risk and control if it occurs

Iain Richards — Tue, 05 Jan 2021 12:54:36 GMT

I played with midazolam quite a lot in the past and really took to using it in all high risk sick animals. Following a pre-med it was good to give just before the induciton agent and reduced the induction dose needed. I did it once on a well animal - sight hound getting thio - disaster!! So for the reasons David cites, it was only ever done to reduce the impact in the sick.
As a fudge factor in guessing horse doses for field anaesthesia it works well, but they are hit with big dom/torb doses

RE: Emergence delirium following dog castration - reflection - any advice how to reduce risk and control if it occurs

Carl Bradbrook — Fri, 01 Jan 2021 14:02:27 GMT

Hi Ben,

As Emily mentions it takes time for the team to become accustomed to the changes in monitored parameters seen following switching from ACP to an alpha-2. The main differences initially observed will be an often profound bradycardia due to peripheral vasoconstriction and subsequent hypertension. This results in pale mucous membranes, which can certainly be worrying if ACP was previously used. Blood pressure measurement can be challenging due to the bradycardia, particularly if a bradyarrhythmia is present. In a healthy adult dog (or cat) blood pressure will be high or high end normal following alpha-2 administration.

In the case you describe, I would also avoid benzodiazepines in the premed. There is a risk of disinhibition in healthy, adult dogs and cats which can add to problems in challenging cases. Options to add to the alpha-2 opioid IM combination, as mentioned would be to include a low dose of ketamine (0.5-1mg/kg) or acepromazine (0.01mg/kg). I would also suggest to ensure sufficient time is given for any IM combinations to be fully effective, monitoring the patient closely but leaving them in a quiet environment where possible.

It may be that following induction of anaesthesia with propofol, that the dog remained at a light plane of anaesthesia, which often results in periods of apnoea, or the alpha-2/opioid premed and then amount of propofol given resulted in the patient being deeply anaesthetised and therefore apnoeic. You mention HR and BP were unstable- was this a bradyarrhythmia? I find it useful to monitor HR and PR in these cases- if you have an ECG you can measure HR and then PR with either a pulse-oximeter or by pulse palpation. The bradyarrhythmia often leads to the rate changing and a more accurate pulse palpation or use of two monitoring methods can provide reassurance that the changes are not as worrying as they may appear.

I always recommend to only consider using atipamezole during anaesthesia as a last resort, as it usually results in further problems with maintaining depth of anaesthesia and a poor recovery. As you found in this case in the recovery period you are left with only your opioid on board. This will be very different to the situation with ACP due to its long duration of action. We find alpha-2s often have to be re dosed during procedures over 60-90 mins, and often re dose in the recovery period to ensure a smooth transition. In this situation low doses of 1-2mcg/kg medetomdine or dexmedetomidine will be useful. I would look at HR, BP and as mentioned elsewhere in the thread ETCO2 (if available) as to markers of patient stability. If BP, ETCO2 and depth of anaesthesia are all stable and appropriate then I would not consider atipamezole.

It very much sounds like you were dealing with emergence delirium in this case, which you could have seen with any patient and therefore is less likely to be simply due to the patient alone.

RE: Emergence delirium following dog castration - reflection - any advice how to reduce risk and control if it occurs

Arlo Guthrie — Tue, 29 Dec 2020 10:40:49 GMT

Don't worry Ben, that's what I am here for, and it was no trouble at all!

RE: Emergence delirium following dog castration - reflection - any advice how to reduce risk and control if it occurs

Benjamin Alyoshkin — Mon, 28 Dec 2020 21:49:46 GMT

Hi Arlo

Thank you very much for letting me know. Sorry about my using the tangent button, for the inconvenience this caused, and thank you very much for your help!

Warm regards

Ben

RE: Emergence delirium following dog castration - reflection - any advice how to reduce risk and control if it occurs

Arlo Guthrie — Mon, 28 Dec 2020 10:13:28 GMT

Benjamin Alyoshkin - Hi Benjamin ... looks like you accidentally replied to a lot of comments in this thread using the tangent button, which then created a whole new lot of tangent threads, rather than keeping the discussion in this thread.

I have moved all of your posts back into this thread, and another reply from Emily. But please when you reply, please press the 'REPLY' link, not the one marked 'TANGENT' unless you very definitely want to start a new discussion topic!

RE: Emergence delirium following dog castration - reflection - any advice how to reduce risk and control if it occurs

Emily Rainbow — Mon, 28 Dec 2020 10:10:10 GMT

[quote userid="13186" url="~/001/veterinary-clinical/small-animal/anaesthesia/f/discussions/29561/emergence-delirium-following-dog-castration---reflection---any-advice-how-to-reduce-risk-and-control-if-it-occurs/227442#227442"]Hi Emily, your comment re this being a consequence of reversing alpha-2 makes more sense the more I think about it. Sadly, I do not have the anaesthetic sheet. The changes occurred during the pre-op preparation, before the dog was moved to the theatre. Surgical nurse reported that HR and BP were low and going down rather than being low but stable. We initiated ivft at 10ml/kg. There were two episodes of breath holding 2 min each, necessitating ippv, so I consented to reverse, giving initially half the amount of atipam. Having said that, there is another dimension to it - somebody else did comment on nurses' perception of CVS instability under alpha-2, so more follows below. Thank you[/quote]

Yes it’s taken a lot of coaching and reassurance for my nurses to be comfortable with the changes seen vs the ACP we used to use.

Bradycardia will occur due to the vasoconstriction caused by the alpha-2, don’t fight it! Unless it’s a puppy this is of no consequence as long as the rest of the cardiovascular parameters are ok - pulse ox, etco2, bp etc. Do not let them panic at the membrane colour either as this will change due to peripheral vasoconstriction.

I would also consider whether the breath holding caused panic and whether the additional IPPV actually deepened the GA too much causing the hypotension issues seen. Do you have etco2 to see whether the breath holding was actually an issue? It may be reassuring to your nurses to allow the dog more time to spontaneously breath if the capnograph is otherwise normal.

I would also consider the approach to hypotension under GA. I would always check GA depth first, try and reduce inhalant gases where possible as these are often the cause (use additional analgesia if too painful to reduce gases), then try fluid bolus and see if fluid responsive. Alpha-2s should preserve BP (despite the reduction in cardiac outflow) due to the vasoconstriction effect so my gut feeling is that something else was to blame for the hypotension.

RE: Emergence delirium following dog castration - reflection - any advice how to reduce risk and control if it occurs

Benjamin Alyoshkin — Mon, 28 Dec 2020 10:07:55 GMT

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This is commonly seen with dogs where the alpha-2 has been reversed in my experience. They wake up far too quickly and panic.

When I do see this happen following ‘normal’ anaesthetics I will give an additional 5ug/kg medetomidine ASAP which I find leads to a smoother recovery.

Can you go into more detail as to the changes you had under GA that led to you reversing the dog? We’re there perhaps other strategies you could have used and left the alpha-2 on board?

[/quote]

Hi Emily, your comment re this being a consequence of reversing alpha-2 makes more sense the more I think about it. Sadly, I do not have the anaesthetic sheet. The changes occurred during the pre-op preparation, before the dog was moved to the theatre. Surgical nurse reported that HR and BP were low and going down rather than being low but stable. We initiated ivft at 10ml/kg. There were two episodes of breath holding 2 min each, necessitating ippv, so I consented to reverse, giving initially half the amount of atipam. Having said that, there is another dimension to it - somebody else did comment on nurses' perception of CVS instability under alpha-2, so more follows below. Thank you

RE: Emergence delirium following dog castration - reflection - any advice how to reduce risk and control if it occurs

Benjamin Alyoshkin — Mon, 28 Dec 2020 10:06:23 GMT

[quote userid="3169" url="~/001/veterinary-clinical/small-animal/anaesthesia/f/discussions/29561/emergence-delirium-following-dog-castration---reflection---any-advice-how-to-reduce-risk-and-control-if-it-occurs/227398#227398"]

I've seen this with methadone and know others who've stopped using it for this reason.

You reversed the alpha 2.

Why was the dog asleep for more than 30 mins for a castration? Seems unusually long.

How heavy was the dog? Small dogs need higher doses of medetomidine.

I think if you're to the point of requiring "moderate restraint" for a cannula, give more sedative and more time.

In my general practitioners view - good pre-med = good anaesthetic. I don't think you achieved that.

[/quote]

Hi Michael, castration was about 30 minutes but the GA probably around 1 hour, pre-med administered good half an hour prior to induction (including waiting time and placing iv catheter). He was nearly 11kg, BCS 4.5-5/9. Fair comment re giving more time if the patient requires restraint after pre-med. Thank you

RE: Emergence delirium following dog castration - reflection - any advice how to reduce risk and control if it occurs

Benjamin Alyoshkin — Mon, 28 Dec 2020 10:05:01 GMT

[quote userid="4367" url="~/001/veterinary-clinical/small-animal/anaesthesia/f/discussions/29561/emergence-delirium-following-dog-castration---reflection---any-advice-how-to-reduce-risk-and-control-if-it-occurs/227411#227411"]

Bad Luck!

The midazolam may have reduced inhibitions before any sedative effect of the methadone and alpha-2 kicked in. It's aleady a hyped animal. The 4mg/kg dose is for he premeded animal, which this dog isn't. . Breathholding so iso conc not reached. Excitation on recovery (which is wher the midazolam might have been helpful) as no premed to help having reversed the alpah-2 (for justifiable reasons if BP falling, although I'd have thought it was up with all the curculating adrenaline).
It sounds like a chain reaction , one error leading to others. Not a blame, just stating it.

To me the key error is an inadequate premed for the patient, in hind sight, abaondon the procedure and try again with a bigger dose. What's the rationale for the midazolam?

Or it could be a cockerpoo with cocker rage, whcih some folk feel is a form of epilepsy. It's behavior needs waching

[/quote]

Hi Iain, I quite like including midazolam to reduce the CVS effects (dog already an athlete), potentiate sedation (frightened dog with a history of defensive behaviour). I agree, we certainly did not help the dog trying to rush through with him being in a high emotional state, not allowing enough time for pre-med to have its effect. Thank you!

RE: Emergence delirium following dog castration - reflection - any advice how to reduce risk and control if it occurs

Benjamin Alyoshkin — Mon, 28 Dec 2020 10:03:56 GMT

[quote userid="8991" url="~/001/veterinary-clinical/small-animal/anaesthesia/f/discussions/29561/emergence-delirium-following-dog-castration---reflection---any-advice-how-to-reduce-risk-and-control-if-it-occurs/227412#227412"]

Avoid any benzos for nervous dog, leads to disinhibition and worsening of aggression.

Acp/alpha2/opioid premed useful for these. Or swap ketamine for acp and you can essentially anaesthetise im and there's a slower recovery.

GA does sound long, peripheral BP with medetomidine is a pointless distraction, nurses always want to reverse alpha 2s, but if the dogs stable you're essentially de-pre-medding it which for a nervous aggressive animal doesn't make sense. In these often don't reverse at all, allow them to go home as soon as ambulatory, let them sleep it off at home.

[/quote]

Hi David, I thought that giving higher end of benzodiazepines' dose range helps to reduce the risk of paradoxical effects, but I may be wrong. I also completely share your comment that some nurses do want to reverse alpha-2 too soon. On this occasion, the surgical nurse questioned if using medetomidine was an optimum choice as the full-time staff seem to elect for ACP at the hospital in question. Thank you!

RE: Emergence delirium following dog castration - reflection - any advice how to reduce risk and control if it occurs

janine redman — Thu, 24 Dec 2020 21:32:54 GMT

There is a tendency for several of the vets and nurses at my practice to want to reverse medetomidine whereas I find the sedation and analgesia should contribute to a more stable protocol in most patients , certainly with a low dose . I find methadone can cause bouts of breath holding and the anaesthetic depth becomes variable . PPV May be required to achieve adequate depth of anaesthesia and an experienced nurse is helpful .

I tend to use buprenorphine and medetomidine sometimes with a small amount of ACP in anxious or aggressive patients especially young healthy ones. The additional local anaesthetic achieves adequate analgesia especially with additional NSAIDS so I don’t feel methadone is necessary.

RE: Emergence delirium following dog castration - reflection - any advice how to reduce risk and control if it occurs

Benjamin Alyoshkin — Thu, 24 Dec 2020 18:09:48 GMT

RE: Emergence delirium following dog castration - reflection - any advice how to reduce risk and control if it occurs

David Mills — Wed, 23 Dec 2020 23:33:53 GMT

Avoid any benzos for nervous dog, leads to disinhibition and worsening of aggression.

Acp/alpha2/opioid premed useful for these. Or swap ketamine for acp and you can essentially anaesthetise im and there's a slower recovery.

RE: Emergence delirium following dog castration - reflection - any advice how to reduce risk and control if it occurs

Iain Richards — Wed, 23 Dec 2020 22:09:00 GMT

Bad Luck!

To me the key error is an inadequate premed for the patient, in hind sight, abaondon the procedure and try again with a bigger dose. What's the rationale for the midazolam?

Or it could be a cockerpoo with cocker rage, whcih some folk feel is a form of epilepsy. It's behavior needs waching

RE: Emergence delirium following dog castration - reflection - any advice how to reduce risk and control if it occurs

Emily Rainbow — Wed, 23 Dec 2020 18:26:09 GMT

This is commonly seen with dogs where the alpha-2 has been reversed in my experience. They wake up far too quickly and panic.

When I do see this happen following ‘normal’ anaesthetics I will give an additional 5ug/kg medetomidine ASAP which I find leads to a smoother recovery.

Can you go into more detail as to the changes you had under GA that led to you reversing the dog? We’re there perhaps other strategies you could have used and left the alpha-2 on board?

RE: Emergence delirium following dog castration - reflection - any advice how to reduce risk and control if it occurs

Michael Woodhouse — Wed, 23 Dec 2020 17:26:53 GMT

I've seen this with methadone and know others who've stopped using it for this reason.

You reversed the alpha 2.

Why was the dog asleep for more than 30 mins for a castration? Seems unusually long.

How heavy was the dog? Small dogs need higher doses of medetomidine.

I think if you're to the point of requiring "moderate restraint" for a cannula, give more sedative and more time.

In my general practitioners view - good pre-med = good anaesthetic. I don't think you achieved that.