Atropine as a premed

Re: Atropine as a premed

salome2001 — Mon, 08 Feb 2010 22:32:30 GMT

I'm not an opthalmic surgeon but other than that, I'd echo pretty much Rebecca's sentiments. Used it when I graduated in the early 90's (back in the thio/halothane era), haven't used it in at least 10 years routinely. Have it in the crash box for the occasional bradycardia (thanks Mike for the ballpark guidelines, could you post one for cats as well?) but TBH it keeps going out of date.

Re: Atropine as a premed

Rebecca Elks — Tue, 03 Mar 2009 22:26:02 GMT

As an ophthalmic surgeon I do occasionally see marked bradycardia with the so-called oculocardiac reflex ( vagally mediated). Even so, I no longer routinely premedicate with atropine, although I have been qualified long enough to have started my veterinary career using atropine routinely for small animal pre-meds (ideas have changed over the years). However we do have it to hand in theatre to use if necessary. My first response is however to stop what I am doing surgically and see if HR stabilises and well as the usual anaesthetic checks.

Re: Atropine as a premed

Martin McDowell — Sun, 01 Mar 2009 20:36:04 GMT

In the two surgeries I have worked in we have never routinely used atropine, in fact I only remember giving it once postoperatively to a hypersalivating cat.

In case bradicardia occurs we just closely monitored it but were never forced to give any additional meds, but the posts above to give some food for thought.

As far as the kidney dilemma is concerned I, also, heard that IV fluids are more important in view of BP rather than HR. But of course, we have all learnt that SOP can change.

Re: Atropine as a premed

Kevin Castle — Wed, 25 Feb 2009 14:36:42 GMT

Thanks for the feedback. I appreciate all the advice/opinions you guys are prepared to give

Re: Atropine as a premed

Mike Martin — Wed, 25 Feb 2009 13:31:32 GMT

Hey, we had a dog yesterday with a bradycardia during GA too. A whippet with a pulmonic stenosis for balloon valvuloplasty. HR began at 40/min following induction with propofol (premed, ACP/Morphine). Maintained on Iso, N2O and O2.

My first thought was maybe he over reacted to the propofol, so give it time. We had an arterial line and because the pressure was good - I was happy. HR dropped to 35. So our first step was to lighten the GA, ie turn down the iso. Over 15-20 mins we got it down to 3/4%. HR settled at 40-45. As long as the arterial pressure was good, colour was good, pulse ox >95%, I was happy. I'm not comfortable with messing with too many drugs which add to the complications and confusion. So we continued - intervention went fine. No problems. As we were suturing up (~90mins later), the dog's HR began to increase and he came light. On fininshing, he woke up well.

So when does the bradycardia worry me? I guess < 50/min I'm watching. <40/min I'm altering the GA in some way, eg lighten. At all stages greatly depends on blood pressure, other factors such as colour/pulse ox etc. If I don't get an art line, I'll use an oscillometric cuff - I realy like BP for monitoring the GA.

Re: Atropine as a premed

beldather — Tue, 24 Feb 2009 11:32:23 GMT

Kevin,

30 is quite low, but then it would depend on fitness levels as well (my first job we had nothing but working dog, their resting rate was about 50bpm for some of them, before meds).
Personally with that I'd just keep a good eye on blood pressure and any pulse deficits. If all fine, then I'd be a bit more relaxed. Never been a big fan of the pulse ox for any type of monitoring unless thorax is open.

Regards

Blair

Re: Atropine as a premed

Kevin Castle — Tue, 24 Feb 2009 10:32:33 GMT

[quote user="Mike Martin"]I prefer to save it for treatment of a bradycardia - although that is rare.[/quote]

Ok, I see the consensus is that Atropine is not necessary as a routine pre-med - this I now accept. BUT when does a slow heart rate actually become a significant (pathologic) bradycardia. We had a boxer yesterday, gave a pre-med of reduced dose ACP + Vetergesic + Metacam (all given approx 30-40mins pre-GA) and induced slowly with propofol and its heart rate dropped to 30 bpm although SpO2 was fine. Is this acceptable or are Boxers a special case where either ACP is to be avoided or often will need Atropine?

Re: Atropine as a premed

beldather — Sat, 21 Feb 2009 14:25:06 GMT

[quote user="Phil Elkins"] no one however has come up with an appropriate rationale for this and I still continue to give mine pre-op. I believe it may be due to the effects of reduced renal perfussion intra-op and the increased risk of kidney damage [/quote]

That appropriate rationale is as you stated, to prevent possible damage to kidneys due to poor perfusion. Intra-op fluids do not absolutely prevent poor perfusion, but they do help reduce the chance of it occuring, even with blood pressure monitoring (very few vets I would think do direct pressure measurements).
So on the basis that we can not guarantee to not cause perfusion problems with anaesthesia why take the risk of using an NSAID pre op, if your using good analgesia anyhow.
It's a balancing act of harm vs benefit, and everyone needs to make the decision of what they think is likely to cause the biggest problems.

I also do not routinely use atropine for premeds (eye enucleation is about it really) as I was taught that bradycardia in presence of normal blood pressure is of little concern. That makes sense to me so have stuck with that protocol (always ACP/Methadone prior to UK, acp/vetergesic since being here).

Regards

Blair

Re: Atropine as a premed

Phil Elkins — Wed, 11 Feb 2009 20:52:28 GMT

In New Zealand atropine is used as a standard alongside ACP/Morphine to prevent morphine induced bradycardia, particularly in older animals. I have never envisaged a major problem in previous anaesthetics without atropnie in the UK, but never had top spec monitoring equipment. Certainly at college with ECG monitoring, BP monitoring and regular blood gasses, atropine was not used as a routine.

As an aside, in New Zealand they have moved away from pre-op NSAID and now give them 4 hours post op as this is the current teaching from Massey. no one however has come up with an appropriate rationale for this and I still continue to give mine pre-op. I believe it may be due to the effects of reduced renal perfussion intra-op and the increased risk of kidney damage (although most animals have intra-op fluids)! As Tennyson said "Ours is not to question why; ours is just to do or die"!

Re: Atropine as a premed

james hunt — Tue, 03 Feb 2009 23:14:01 GMT

Isoflurane is a relatively irritant ether however does not usually produce enough airway irritation to require atropine to dry secretions.

Atropine is commonly used for premedication in US to reduce incidence of opioid (hydromorphone, oxymorphone) induced bradycardia.

For most opioids in common use for premedication in UK, i don't find a significant degree of bradycardia. (morphine, methadone, buprenorphine)

I use fentanyl/alfentanil relatively frequently and these potent opioids consistently produce bradycardia. In healthy adult animals I will usually tolerate a degree of bradycardia as long as blood pressure remains good (it generally does). Giving anticholinergics can produce tachydysrhythmias which can affect cardiac output (reduced ventricular filling) and increase myocardial work/oxygen demand.

In paediatric animals, cardiac output tends to be heart rate dependent so have a narrower tolerance for drops in HR.

If you do need to use anticholinergic consider glycopyrrolate?

Re: Atropine as a premed

Mike Martin — Tue, 03 Feb 2009 09:00:06 GMT

You're not alone in doing this, I've met a handful of pracititioners who also do this. But like others who have responded, I don't, and I'm aware of no problems. I prefer to save it for treatment of a bradycardia - although that is rare. Even if the bradycardia was at the end of the op (eg. PDA closure) and surgery was finished, I would give dopram (rather than atropine) to increase the heart rate and arouse the animal. Atropine's duration of action seems very short in my experience and I would doubt you would see a difference in HRs without using it. For your interest, my current sedation regime is posted: http://www.vetsurgeon.org/blogs/martin_referrals/archive/2009/01/05/sedation-of-the-cardiac-case-our-current-regime.aspx

Re: Atropine as a premed

Kevin Castle — Mon, 26 Jan 2009 13:42:17 GMT

We were taught that Atopine would prevent bradycardia during anaesthesia, esecially with abdominal surgery when there may be stimulation of the vagal nerve.

I guess I'll have to get used to slower heart rates under GA now. Maybe Atropine was more important in the days of Thiopentone and Halothane?

Re: Atropine as a premed

Evelyn Barbour-Hill — Sun, 25 Jan 2009 20:06:41 GMT

I used to premed with atropine on every cat (this was conventional advice) until I had a disastrous oesophageal ulceration due to gastric reflux. I never used it again and perceived no difference in anything.

Re: Atropine as a premed

ms1083 — Sun, 25 Jan 2009 19:58:20 GMT

What is the benefit of atropine? We were taught at University that atropine is no longer used as its main advantage was to reduce the salivation caused by ether. However, it has a role in ruminants to reduce the copious salivation and in specific (rare) small animal anaesthetic complications/conditions. Wouldn't imagine you would see any difference not using it on a day to day basis.

Re: Atropine as a premed

Kevin Castle — Fri, 23 Jan 2009 14:06:28 GMT

Dogs and cats. Have had very few anaesthetic deaths in over 20 yrs practice.

Re: Atropine as a premed

Ian Mostyn — Fri, 23 Jan 2009 12:57:00 GMT

What species are you talking about? I have never used atropine in dogs - always gone with acp/opiod/metacam as pre-med. I used to use it in cats (theory being to reduce xs salivation) but not for 8 years now. I was using xylazine then propofol, now I use a lot of medetomidine/butorphanol/ketamine. Can't say I miss atropine, it does have its issues. I keep it in my emergency box and it has helped revive a couple of dogs alongside adrenaline but that is my only recent use.

Ian