How low is too low? Opinions, please....

Re: How low is too low? Opinions, please....

Niall Taylor — Mon, 22 Jul 2013 12:39:56 GMT

[quote user="Braden Collins"]With hypothermia being the leading cause of anaesthetic deaths (sorry, can't find reference)[/quote]

That's quite a bold statement - a reference would be much appreciated.

Niall

Re: How low is too low? Opinions, please....

Hannah Wynne Richards — Mon, 22 Jul 2013 10:20:08 GMT

I wouldn't like to see a tempbelow 37. Try turning the heating up!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

I alsohave a heated op table

Wynne

Re: How low is too low? Opinions, please....

Holly Norman — Mon, 22 Jul 2013 09:13:15 GMT

Agree 35' seems a bit low. I attended a CPD at AHT about anaesthetic complications and one of the interesting points was that lower body temperature prolongs excretionof anaesthetic gas, meaning that cold animals get deeper. Personally I find that animals that have maintained a higher body temperature seem to recover better- I don't know if anyone else has found this?

We use heatpads under a vetbed for all anaesthetics. For dentals, we also use out of date fluid bags pinged in the microwave. One of our nurses injected some green food colouring so they wouldn't get confused with the rest of the fluids and they stay warmer for longer than 'hot hands'/ wheat bags.

Re: How low is too low? Opinions, please....

CatherineThomas — Mon, 22 Jul 2013 07:32:51 GMT

I find that the worst proceedures for heat loss are x-rays. Our x-ray room is at the end of the building and gets quite cold in winter, plus we don't have digital and only one plate so it takes so long to get a series of views with all of the re-positioning etc so difficult to keep wrapped in a blanket etc. Particularly when we take x-rays first and then move on to surgery or dental proceedures.

One of the things our nurses do is to put baby socks over their paws to reduce heat loss. I'm not sure where this idea came from or if it has any benefit, but the nurses seem quite keen on it. We have heat mats which have their own fleecy cover which then has a towel and an inco pad over the top for during surgery and we have electric heaters which are placed in the kennels on cold days, and to heat the x-ray room up before we use it.

Re: How low is too low? Opinions, please....

Braden Collins — Mon, 22 Jul 2013 07:10:00 GMT

With hypothermia being the leading cause of anaesthetic deaths (sorry, can't find reference), a Bair Hugger is an excellent investment. We added a few dollars to our theatre fee to cover the cost of the unit and blankets (you can use the blankets for several days if you're careful) and absolutely love it. The animals wake up so much quicker and smoother, the small dogs and cats have very stable anaesthetics and I would hate to be without it now. We got ours as a reconditioned unit from the children's hospital so wasn't too expensive and you can get generic blankets to reduce the cost.

Re: How low is too low? Opinions, please....

Utlendigur — Sun, 21 Jul 2013 23:43:12 GMT

[quote user="Anthony Todd"]

[quote user="Utlendigur"](but only under a vetbed).[/quote]

Trouble is when it gets wet, as others have said; direct heat transfer and total contact, like boiling an egg...

[/quote]

We often have inco-pads on top of the vet bed so the vetbed stays dry

Re: How low is too low? Opinions, please....

Anthony Todd — Sun, 21 Jul 2013 23:36:59 GMT

[quote user="Utlendigur"](but only under a vetbed).[/quote]

Trouble is when it gets wet, as others have said; direct heat transfer and total contact, like boiling an egg...

Re: How low is too low? Opinions, please....

Utlendigur — Sun, 21 Jul 2013 23:31:06 GMT

One tip we have found helps is to have vetbeds in the kennels from the time the animal is admitted, because they start to drop their temperature as soon as the premed takes effect. We quite often use bubble wrap on the table/round the animal, heat pads/snugglesafe (but only under a vetbed).

Re: How low is too low? Opinions, please....

Anthony Todd — Sun, 21 Jul 2013 22:54:25 GMT

We have had severe thermal burns from microwaved heat pads and the use of hot hands [rubber gloves filled with "hot" water] which have been shown to cause burns at 45C. Even low temp pads can cause them together with the fact that they notoriously unreliable with regard to constant temperature.

We rely on the animal moving away when too hot which doesn't happen under GA

Of course burns are a function of temperature multiplied by time and I seem to remember the lowest "burn temp is somewhere around 40C.

I was always a bit sceptical when raising body temp was discussed as, I believe, major heart surgery is done with the body temp lowered deliberately, even in neonates.

But maybe I've got it wrong.

I reckon often the risk of a burn outweighs the possible benefits.

Re: How low is too low? Opinions, please....

Rob Loxley — Sun, 21 Jul 2013 22:19:44 GMT

[quote user="John Flynn"]I think 35'C is all to common, but far from ideal.[/quote]

Agreed; we aim to keep >37C. We use low-power electrically heated pads; as for burn risk, always a vet bed on top of the pad and be very careful about the animal/bed getting wet (e.g. c/section) as heat conduction goes up. Forced warm air ventilation would be nice but isn't cheap when you consider multiple animals and pre and post op.

Other things to think about are putting a blanket over any exposed bits of animal, looking hard at ambient temperature (esp having the aircon on full blast in the hot weather!), warming any fluids and anaesthetic heat/moisture exchangers. And for all of this start preop (incl. don't underestimate how cooling lying on a steel kennel is) and continue postop.

Re: How low is too low? Opinions, please....

Glen McIntosh — Sun, 21 Jul 2013 22:02:29 GMT

Saw an interesting presentation at a conference a couple of years ago:

Physiology and Prevention of Perianesthetic Hypothermia

International Veterinary Emergency and Critical Care Symposium 2011

Matt Read, DVM, MVSc, DACVA

University of Calgary, Calgary, AB, Canada

The article is available in the 2011 IVECCS proceedings on VIN.

Worth a read.

I could email you a copy if you want.

Upshot is that actually the best way to prevent hypothermia in shorter anaesthetics (<1 hour) is to pre-warm the patient prior to induction. Warming blankets etc, inc bair huggers, will not prevent heat loss during this initial 1 hour period, but ARE useful in preventing hypothermia in longer proceedures and in warming patients up after anaesthetics.

From Physiology and Prevention of Perianesthetic Hypothermia, International Veterinary Emergency and Critical Care Symposium 2011, Matt Read, DVM, MVSc, DACVA:

"One technique that can be used to minimize intraoperative hypothermia is "pre-induction warming". Prewarming is a well-documented technique for preventing redistribution heat loss during the first hour of anesthesia of human patients. It is based on the observation that if the patient's periphery is warmed prior to anesthesia, the heat loss that typically occurs during the first hour of anesthesia (Phase 1) is lessened since there is a smaller temperature gradient between the body's normally cooler periphery and its warmer core. To use this method, a forced-air warming blanket is wrapped around the patient prior to anesthesia (i.e., while they become sedated following premedication) instead of simply applying the warming blanket after the induction of anesthesia (as is usually the case in most veterinary practices). This method works very well to minimize or actually prevent hypothermia entirely in many patients, especially during the first hour of anesthesia when much of their heat is lost. This is where having an understanding of the physiology behind hypothermia is crucial to actually making a difference to your patient - think about how long your procedure will last when you are deciding how to combat hypothermia. If you are performing a short procedure (< 1 hour), solely applying a warming technique after the induction of anesthesia will be ineffective, since redistribution heat losses that occur during this time can only be prevented by preinduction warming. A forced air warming device may help warm the animal up after the procedure, but it will not stop the heat loss from occurring first."

It also talks about "flexible resistive-polymer blankets" as being as effective as forced-air warming blankets (Bair huggers). By this they mean the "Hot Dog" blankets. We use these "hot dog blankets" and find them to be easier, more convenient and as effective as bair huggers. I think they are cheaper as well.

http://www.vetwarming.com/

Don't know if they are in the UK though.

Also, things like hot water bottles and microwave heat pads/bean bags etc really don't help prevent perioperative hypothermia at all, and as others have pointed out, can be quite dangerous.

Re: How low is too low? Opinions, please....

John Flynn — Sun, 21 Jul 2013 21:23:07 GMT

If you have an assistant to monitor the anaesthetic and rectal temperature of dentals, I find equipping them with a blanket and hair-dryer cheap and cheerful assuming the procedure will take time.

Easier to stop temperature going too low than raise it again I find.

I think 35'C is all to common, but far from ideal. On the plus side anaesthetic requirements will have reduced markedly at this temperature

Re: How low is too low? Opinions, please....

Stephen Courtney — Sun, 21 Jul 2013 21:21:26 GMT

We use Bair huggers for these guys. Had a couple of nasty burns from microwave heated products where they have been overheated or perhaps not wrapped up enough - too unpredictable maybe? Anyhoo we banned them.

Other alternatives are bubble wrap and foil, and heated mats, gloves filled with warm water etc.

FWIW i think 35 is probably too low for an elderly animal undergoing a lengthy procedure - what are their recoveries like? If they are OK then maybe not a big deal for most cases, but you'll often get the odd fragile one where it is.

You might also find using local anaesthetics (and good opiods/ nsaids ) during the dental procedures will allow you to use less anaesthetic agents which can make the anaesthesia far smoother

Re: How low is too low? Opinions, please....

Francisco Gomez — Sun, 21 Jul 2013 21:19:02 GMT

I think 35C is quite low but we sometimes get it too with long dentals. We had invested in a bair hugger and it does wonders. Now... I'm sure you know this, but I will say it anyway. Burns due to heated wheat bags and electric heating pads are not defensible. I believe that it is better to have a patient a bit low rather than having a burn. (Well, none, if you can avoid it)

We did have a burn (presumably) during a ga dental that I was doing (I was not concentrating on the patient temp and heating methods, that is what the QVN is for). It took a couple of months for this poor dog to heal his burns and expensive treatments. All of this at the expense of the practice, of course. Now the bair huggers don't seem that dear, do they?

*edit*

You could have burns with the 'hugger' as well, but I think they're safer...