Anaesthetic circuits for Cats

Re: Anaesthetic circuits for Cats

Nick Shackleton — Sun, 15 Nov 2009 22:46:59 GMT

Hot hands are good wrapped around your fluid line (not gloves thou) the use of a 500ml bag of saline heated up in a microwave. it can then be reheated as required and less likely to get pierced and the patient covered in either hot water or freezing cold water!!!! From wot I've read before sounds like you all you can to reduce risk of heat loss.

re: Dumping! I usually run my cicle as a semi-closed circuit. so if I want to give the patient a breath just close the valve fully and give a small breath. Do u have a manometer on you circles?? you should ideally only give a breath of 10-20cm/h2o pre breath.

As a general rule I use 4-8litres/min depending on the size of my patient. usually with a 2litre bag or 4 litres for the big dudes! usually use this flow rate for the first 15-20 mins and then reduce down, this ensure plenty of time for denitrogenation to take place. Also remember that if the patient is moved you should increase flow rates back up.

And yeah a Bain is a circuit for dogs 15kg plus!

Re: Anaesthetic circuits for Cats

Freckle — Sun, 15 Nov 2009 22:22:14 GMT

Really? Re the bain!! Either that is a typo on the wall at work, or I have been reading it wrong for months! Probably the latter!

Fair enough re the HME - the only anaesthetist I have ever worked with hated them, and that has rubbed off on me - would be interested in learning differently though, as we have them at work, but they never get used. We have no heated table, or bair hugger, and our heatpad is tiny and ineffective, so any ideas on maintaining normothermia uga would be great!

Re the circle - by 'dumping' do you mean fully opening the valve and emptying the reservoir bag? Can this method be used to give a one off breath with the circle?

This conversation is causing grey matter to stir - changing on to a different topic but still with circles - denitrogenation - I have always done double flow rates for the first few minutes? This is right? Right? lol! We only have o2 and iso in current practice, but many moons ago, I used circles with N20 and capnography, and I'm sure that is what we were told then. This still applies without N20 doesn't it? I've been doing it anyway - I would think that increased O2 for a few mins wouldn't cause any harm if I am muddled - Again!! Lol

Re: Anaesthetic circuits for Cats

Nick Shackleton — Sun, 15 Nov 2009 22:07:07 GMT

Bain is for 15kg plus not up to 15kg (so think you may of got a bit confused???)

Regards to HME I think it is down to personal preference, some anaesthetists like them some don't. Much like T-pieces with valves, some like them some don't. I prefer them through reasons taught to me. Yes they do increase dead space/resistance (but if you got a 2.5kg patient every 0.1 of degree that you can keep in the patient the better.

Regarding the circle. Iso concentrations can be changed quickly by dumping the gas in the bag and increasing your fresh gas flow rate.

Re: Anaesthetic circuits for Cats

Freckle — Sun, 15 Nov 2009 21:58:38 GMT

[quote user="Nick Shackleton"]

Also the use of Heat and Moisture Exchangers (HMEs) and heat reduce the amount of heat loss.

[/quote]

I did spend a few months once working with a veterinary anaesthetist (and constantly barraged him with questions lol), and he was not a fan of these, due to increase in resistance and dead space...?

Re: Anaesthetic circuits for Cats

Nick Shackleton — Sun, 15 Nov 2009 21:56:32 GMT

[quote user="Maisy"]

[quote user="Nick Shackleton"]

nothing much to add to be honest except that you can safely use N2O and O2 in a circle provided you use 50/50 concentrations and have capnography to measure inspired gases!

[/quote]

Bah, we didn't have a capnometer! Had to fight tooth and nail for a pulse ox, we would have had to wait another 100 years for another piece of equipment!

[/quote]

Awwwwwwwww poor maisy

Re: Anaesthetic circuits for Cats

Freckle — Sun, 15 Nov 2009 21:56:24 GMT

Thanks for the replys - very interesting re temp maintenance with circles - will bear that in mind in the future!

I knew that about the lack, but I didn't anticipate having to perform ippv for any length of time, just wanted to be able to give the odd breath if necc - can you do that with a rebreathing circuit? I always thought not...? I also wanted to be able to change the iso concentration quickly if needed - my understanding is that it takes significantly longer for the inhaled gas to reach the same concentration as the vaporiser with rebreathing circuits? Hence why I chose a non-rebreathing circuit. I would have much preffered the bain as I am more familiar with it, but we have a bsava manual photocopy on the wall at work that said they should only be used up to 15kg. Incidentally, what should be used for ippv in large patients?

Re the BP - thanks for the info! I'll try pushing for some equipment at work! We don't measure tbv, or weigh swabs, but to be honest there wasn't a great deal of blood loss apparent - perhaps 3 x 10cm swabs soaked through? And no great blood loss around the site.

Thanks again for the help - all my anaesthesia knowledge has been learnt on the job or from books or harrasing colleagues - can not WAIT to study it at college! I think it's the next module we're doing - whoooo!

Re: Anaesthetic circuits for Cats

Maisy — Sun, 15 Nov 2009 21:53:08 GMT

[quote user="Nick Shackleton"]

nothing much to add to be honest except that you can safely use N2O and O2 in a circle provided you use 50/50 concentrations and have capnography to measure inspired gases!

[/quote]

Bah, we didn't have a capnometer! Had to fight tooth and nail for a pulse ox, we would have had to wait another 100 years for another piece of equipment!

Re: Anaesthetic circuits for Cats

Nick Shackleton — Sun, 15 Nov 2009 21:42:31 GMT

[quote user="Maisy"]

[quote user="Freckle"]

does a rebreathing circuit make a significant difference to temp maintenence whilst uga? enough to go without the ippv option in a risky ga? i'm not being purposefully arsey lol! i am genuinley interested :)

[/quote]

I would say so, I tested this with a few patients just out of interest (dogs only, between using circle and Bain). The temperature remained more stable during lengthy procedures when a circle was used as the constant inhaling of cold gases is reduced by far. It's not that often though where IPPV is essential for long periods of time so you could use the circle for this briefly.

That's just my view though, I like circles! I only really use Bains/Lacks if likely to be using N2O with it. Nick has anaesthesia bods at work though so may have some more helpful info!

[/quote]

nothing much to add to be honest except that you can safely use N2O and O2 in a circle provided you use 50/50 concentrations and have capnography to measure inspired gases!

If we have a patient that requires long periods of IPPV they end up on the ventilator! and I kno it's not really available in GP.

Also the use of Heat and Moisture Exchangers (HMEs) and heat reduce the amount of heat loss.

Re: Anaesthetic circuits for Cats

Nick Shackleton — Sun, 15 Nov 2009 21:31:35 GMT

RE: BP: It is difficult to accurately assess mean arterial blood pressure in small animals, althou can be more successful in horses.

You don't have to buy any fancy equipment to measure BP. You need several different sized BP cuffs, a Sphigmometer and a stethoscope (that's how my dr used to check my BP)

Fluids sounds good. If BP is low you can give a bolus of crystalloids @ 10/ml/kg to help increase BP. and then move onto collids.

Do you ever work out TBV (Total Blood Volume)?? 90mls/kg (dogs) 60-70mls/kg (cats) Weighing blood soaked swabs can be quite scary. at 10% blood loss you should be thinking about colloids.

regards to temp. sounds like you did all you could.

BTW a lack is inefficient for performing IPPV long term. so therefore a circle or a bain would be more appropriate.

Re: Anaesthetic circuits for Cats

Maisy — Sun, 15 Nov 2009 21:28:45 GMT

[quote user="Freckle"]

[/quote]

That's just my view though, I like circles! I only really use Bains/Lacks if likely to be using N2O with it. Nick has anaesthesia bods at work though so may have some more helpful info!

Re: Anaesthetic circuits for Cats

Freckle — Sun, 15 Nov 2009 21:07:07 GMT

sorry - we didn't have BP monitoring equipment- the vet and i deduced the BP was low due to the poor quality of peripheral pulses compared to more central ones (which were still pretty crap, but less so than peripheral)

re fluids, the dog was on 100mls/kg/24hrs pre surgery, and 10mls/kg/hr during surgery - vet didn't want to increase it any further, I used heat pads, bubble wrap, booties, warmed fluids at point of entry etc etc to try and keep temp as high as possible, but she was still hypothermic during and post op.

Re: Anaesthetic circuits for Cats

Nick Shackleton — Sat, 14 Nov 2009 00:08:40 GMT

Forgot to say I would prob of chosen a circle. due to being able to use low flow rate this will allow to retain temperature lost due to open abdomen.

Re: Anaesthetic circuits for Cats

Nick Shackleton — Sat, 14 Nov 2009 00:05:58 GMT

prob best thing is to stick to what your comfortable using!

Just outta interest you say the dog had low BP, but you also state no monitoring equipment slightly confussing.

Did you do anything to counteract the low BP??? What fluid rate did you use???

Re: Anaesthetic circuits for Cats

Freckle — Fri, 13 Nov 2009 23:55:14 GMT

I much prefer jackson rees modified t piece (the one with the paediatric teddy bear valve) to mini lacks - probably just because i'm used to them.

what are the pros and cons for each circuit?

also we had an ill geriatric dog ga in today, closed pyo, 22kg - i chose the parallel lack over the circle cause she already had eplilepsy, and i would much rather have a circuit where i could control her iso better (takes time to take effect in a rebreathing circuit right?), and give her the odd breath if needed (not cont ippv - i know the lack isn't suited to that, but circle is less suited for the odd breath!). it wasn't needed thankfully, but it was a horrid ga! pale, weak thready peripheral pulses, and low BP It went OK though, but recovery was prolonged and vocal!

however my HN wanted to use the circle - he went on his lunch, so I used the lack - what would you have chosen? We have no monitoring equipment save stethoscopes and nurses!!

Re: Anaesthetic circuits for Cats

Nick Shackleton — Fri, 13 Nov 2009 21:47:23 GMT

I work on 2.5-3 x MV (minute volume)

MV = TV (tidal volume) x RR (resp rate)

TV = 15 - 20mls/kg

Re: Anaesthetic circuits for Cats

Mrs Dot Dot — Fri, 13 Nov 2009 21:26:00 GMT

Nick... can you tell me what flo rates you should use on a t-piece.... I've always used 200-300mls per kg bodyweight... is this right? thanks

Re: Anaesthetic circuits for Cats

Nicola Birch — Fri, 13 Nov 2009 19:44:40 GMT

Hello Mrs C!!! How the hell are you? Only have T-piece at the mo but am campaining for a mini Lack as much prefer that circuit for the uncomplicated cases as less drag and lower flow rates!

Hugs xx

Re: Anaesthetic circuits for Cats

Carol Cottrell — Thu, 12 Nov 2009 19:57:29 GMT

Thanks everyone!

Re: Anaesthetic circuits for Cats

Nick Shackleton — Thu, 12 Nov 2009 16:57:47 GMT

Spoken to anaesthetist at work today. Said it is ok to use lower flow rates when using a T-Piece provided that inspired carbon dioxide is measured (capnograph) and it does not creep up too high (1-3mmHg is usually acceptable) it should be ok.

Re: Anaesthetic circuits for Cats

Snowb — Thu, 12 Nov 2009 01:02:21 GMT

[quote user="Carol Cottrell"]

Hi Rachel,

Can you do IPPV with the Humphries ADE (am so behind with newer circuits!!)

Thanks, Carol

[/quote]

yes you can

Re: Anaesthetic circuits for Cats

Nick Shackleton — Wed, 11 Nov 2009 22:32:00 GMT

[quote user="Vicky C"]

I think that's why we still have the t-pieces.

[/quote]

Re: Anaesthetic circuits for Cats

Vicky RVN — Wed, 11 Nov 2009 22:26:25 GMT

I think that's why we still have the t-pieces.

Re: Anaesthetic circuits for Cats

Nick Shackleton — Wed, 11 Nov 2009 22:22:01 GMT

Mini lack are good but are inappropriate for IPPV, so make sure you swap to a T-piece if ventilation is required

Re: Anaesthetic circuits for Cats

Vicky RVN — Wed, 11 Nov 2009 22:17:31 GMT

We use mini lack. Do have t-pieces but very rarely used now.

Re: Anaesthetic circuits for Cats

dinkyd — Wed, 11 Nov 2009 22:12:07 GMT

Well im not greedy lol just a pocket size one would do me!