Bradycardia worries!

Re: Bradycardia worries!

Claire Bloor — Fri, 16 Mar 2012 21:02:24 GMT

Good points and advice provided and lots of things to think about.

Don't forget that unexplained bradycardia with no change in anaesthetic depth can be due to vagal stimulation......

Re: Bradycardia worries!

emvn80 — Tue, 28 Feb 2012 14:35:56 GMT

Sorry we couldn't be more useful! Sounds like you have ruled out many things logically. I know it is difficult in a busy general practice but if you have one (in the consulting room cupboard ;-) ) then placing a Doppler would be very helpful to you, will allow you to hear the pulse rate and let you check the BP is alright despite the low heart rate, as without knowing BP it is difficult to say whether you should be concerned or not. The fact the pulse quality is good is a positive thing. Good luck! :-)

Re: Bradycardia worries!

nathalieford — Tue, 28 Feb 2012 07:22:19 GMT

I really appreciate your comments.

I don't know what the dog's heart rates were before premed as the vet checks them and generally writes heart ok on computer which is definately something we need to improve on with heart rates being noted and then i would at least have a starting point. Post premed their heart rates range from 80-100 bpm.

We are able to monitor BP but it's not something we really do, mind you as a hospital i really feel we should. Peripheral pulse was strong and constant throughout however the dog that was castrated did go quite pale. The heart rate did not seem to change significantly once i had reduced the isoflurane. The kennel environment is kept at a constant temp of 24C and prep room and theatre the same so i don't think that it is due to hypothermia but will start doing temp during ops from now on.

It is quite unlikely that the premed bottle could've become contaminated but definately something to think about. We do not dilute the calmivet it's just as it comes and is only used for premeds.

I have experienced fit healthy dogs with low heart rates but i've had old patient's, ill patients all sorts that seem to just drop heart rate after induction.

Re: Bradycardia worries!

emvn80 — Mon, 27 Feb 2012 21:53:12 GMT

[quote user="Sal the 1st"]

yes this is what I was driving at

[/quote] Sal the first- great minds think alike ;-). Although saying that if that was the case then the depth of anaesthesia would appear deeper and they would be obviously profoundly sedated I would have thought?? I'm going with just fit dogs or hypothermia as likely reasons, be good to know what the peripheral pulse quality was like and what body temp was if possible. But if it was me and someone had diluted the Calmivet I'd throw it away just in case! Vagal stimulation would be another option but neither dogs were having surgery which should affect the vagal nerve nor are labs breeds known for having naturally high vagal tone.

Re: Bradycardia worries!

Sal the 1st — Mon, 27 Feb 2012 21:47:31 GMT

[quote user="emvn80"]... Saying that it may be worth double checking that everyone is drawing up the correct volume of premed and not going by the old 2mg/ml ACP. I guess if people were accidently administering the wrong (much higher) dose of acepromazine the dogs would be profoundly sedated and therefore have a lower isoflurane requirement which if you sill delivered the same amount as normal would make them more deeply anaesthetised, which would reduce the heart rate. How are you using the Calmivet? Has someone made up a diluted bottle? Could they have got the dilution wrong? Maybe throw it away just in case?

[/quote]

yes this is what I was driving at

Re: Bradycardia worries!

emvn80 — Mon, 27 Feb 2012 21:38:54 GMT

Just out of interest my own dog is a fit x-breed who has a resting heart rate of 45-50bpm which under anaesthesia drops to around 35-40bpm, but she is fit, healthy with good pulse quality and blood pressure so nothing to worry about! :-)

Re: Bradycardia worries!

emvn80 — Mon, 27 Feb 2012 21:35:00 GMT

... Saying that it may be worth double checking that everyone is drawing up the correct volume of premed and not going by the old 2mg/ml ACP. I guess if people were accidently administering the wrong (much higher) dose of acepromazine the dogs would be profoundly sedated and therefore have a lower isoflurane requirement which if you sill delivered the same amount as normal would make them more deeply anaesthetised, which would reduce the heart rate. How are you using the Calmivet? Has someone made up a diluted bottle? Could they have got the dilution wrong? Maybe throw it away just in case?

Re: Bradycardia worries!

nathalieford — Mon, 27 Feb 2012 21:34:47 GMT

The dog was showing signs of being on a lighter plane of anaesthesia all through the op as the vet kept saying the dog could feel what she was doing as was reacting eveytime she attempted to remove the cyst. I didn't however increase iso due to low heart rate. Got my head nurse to come in as way out of my comfort zone she couldn't explain it either.

Re: Bradycardia worries!

Sal the 1st — Mon, 27 Feb 2012 21:31:07 GMT

I havnt seen it myself but have heard it mentioned. I think it may have been mentioned on here - just off to look. Was the changeover and the incidence of bradycardia around the same time? It might have nothing to do with it at all but might be worth looking into??

Re: Bradycardia worries!

emvn80 — Mon, 27 Feb 2012 21:30:33 GMT

N definitely not... Calmivet is the same drug as ACP (acepromazine) and may cause hypotension by vasodilation but should not drop te heart rate. ... I assume the dogs had a full clinical exam and cardiac auscultation prior to anaesthesia which was normal?

Re: Bradycardia worries!

nathalieford — Mon, 27 Feb 2012 21:28:09 GMT

We have changed from acp to calmivet, is this a common side effect of that drug?

Re: Bradycardia worries!

emvn80 — Mon, 27 Feb 2012 21:28:03 GMT

I would start by saying don't panic! What were the dogs heart rates prior to anaesthesia? 48bpm isn't actually that low in a fit healthy dog, esp a big dog. I would not be overly concerned if the blood pressure is fine. Are you able to monitor blood pressure? What is the peripheral pulse quality like? Acepromazine should NOT reduce heart rate (whether ACP or Calmivet), the dose is reasonably high but it should not drop heart rate - it may drop blood pressure by vasodilation. Opioids cause a drop in heart rate but buprenorphine doesn't normally do this noticeably as it is a partial opioid. When you reduce the iso does the heart rate increase? I assume the dogs could not be cold already? Do you monitor temp? ACP will cause a reduction in body temp (as will anaesthesia obviously) and hypothermia is a common cause of bradycardia. Don't worry too much- I would check some pulse rates prior to induction and compare the before and after- maybe they were just fit dogs? Also check pulse quality/BP - place a Doppler if you have one... A slower heart rate doesn't necessarily mean a reduction in cardiac output or blood pressure in which case it doesn't matter. Also check body temperature under anaesthesia. Try reducing the iso as much as you can. Other things to rule out would be human error- Could the premed bottles have become contaminated with drugs like medetomidine (Domitor) or opiods like methadone which are known to reduce heart rate? Also as an aside- just chck basic things like sodalime is not exhausted, that you are supplying enough oxygen. Do you have a pulse oximeter on? I can't think why this would cause bradycardia but just checking! Hope this helps

Re: Bradycardia worries!

Amy Homer. RVN. NCert A&CC — Mon, 27 Feb 2012 21:14:02 GMT

i have had a few patients that dont seem to loose there blink reflex completely no matter how deep they are so maybe they are a llittle deep. ? also definatly would be worth checking bo and maybe giving an iv bolus. x

Re: Bradycardia worries!

Sal the 1st — Mon, 27 Feb 2012 21:05:21 GMT

have you just changed over from acp to calmivet by any chance? ( I know some practices did order in a lot of acp in anticipation of it not being available)

Re: Bradycardia worries!

nathalieford — Mon, 27 Feb 2012 20:45:47 GMT

Thanks for your reply. The sedation is given i/m at least 20-30 minutes before aneasthesia induction. The only other drug given is a NSAID.

We do not routinely monitor BP. We don't place anything on iv fluids unless it is indicated eg age or other underlying problems.

Re: Bradycardia worries!

Wispa — Mon, 27 Feb 2012 20:29:42 GMT

by what route are you giving the sedation and what is the time difference between giving the sedation and induction? are there any other drugs given at all?

do you monitor the BP of your patients as well? would be interesting to see if there is a corresponding drop in this, which could lead to concerns about renal ishaemia. one of the main side effects of ACP is hypotension which could be a contributing factor. Also, are your patients on iv fluids during anaesthesia?